Co-reporter:Thomas G. Hörner ;Peter Klüfers
European Journal of Inorganic Chemistry 2016 Volume 2016( Issue 12) pp:1798-1807
Publication Date(Web):
DOI:10.1002/ejic.201600168
Abstract
A species model for the copper(II)/L-(+)-tartaric acid (LH2, tartH2) aqueous system between pH 1.9 and 12.3 has been established by potentiometric, UV/Vis spectroscopic, solubility and crystallographic studies. Eight species were detected, including the oligonuclear major species Cu8L6H–10 in the neutral region and the mononuclear major species CuL2H–4 in the alkaline region, the latter being associated with Fehling's solution. The octanuclear complex was isolated as its lithium salt Li7[Cu8(L-tartH–2)4(L-tartH–1)2(H2O)6]NO3·19H2O (1). The “Fehling species” CuL2H–4 was crystallized as its sodium, potassium and caesium salts, namely K2Na4[Cu(L-tartH–2)2]·12H2O (2), Na6[Cu(L-tartH–2)2]·9H2O (3), Na6[Cu(L-tartH–2)2]·14H2O (4), and Cs6[Cu(L-tartH–2)2]·8H2O (5). Each of them shows a distorted square-planar environment of copper(II), similar to the related non-chiral cuprate [Cu(rac-tartH–2-κ2O2,O3)2]6– (S. Albrecht, P. Klüfers, Z. Anorg. Allg. Chem. 2013, 639, 280–284). By comparing the components of the UV/Vis spectra of Fehling's solution and the solids, we confirmed the identity of the major solution species.
Co-reporter:Anna K. E. Gallien, Dominik Schaniel, Theo Woike and Peter Klüfers
Dalton Transactions 2014 vol. 43(Issue 35) pp:13278-13292
Publication Date(Web):14 Jul 2014
DOI:10.1039/C4DT01506A
Two different structure types were found for a series of mononuclear dinitrosyl complexes of the general formula [RuL2(NO)2X]BF4 (L = monodentate phosphane, X = Cl, Br, I). The {Ru(NO)2}8-type target compounds were prepared by the reduction of the respective {RuNO}6 precursors and subsequent oxidative addition of (NO)BF4. About one half of the new compounds share their molecular structure with the hitherto only representative of this class of dinitrosyls, Pierpont and Eisenberg's [RuCl(NO)2(PPh3)2]PF6·C6H6 (Inorg. Chem., 1972, 11, 1088–1094). The Cs-symmetric cations exhibit both a linear and a bent Ru–N–O fragment, in line with a formal 6 + 2 split of the {Ru(NO)2}8 electron sum in the sense of a [RuII(NO+)(1NO−)]2+ bonding. The coordination entity's configuration in this subgroup is described by IUPAC's polyhedral symbol SPY-5. Continuous shape measures (CShM) as defined by Alvarez et al. (Coord. Chem. Rev., 2005, 249, 1693–1708) reveal a uniform deviation from the L–M–L angles expected for SPY-5, in a narrower sense, towards a vacant octahedron (vOC-5). DFT calculations confirmed that Enemark and Feltham's analysis (Coord. Chem. Rev., 1974, 13, 339–406) of the electronic situation of the {Ru(NO)2}8 group remains adequate. The same holds for the second subclass of new compounds the existence of which had been predicted in the same paper by Enemark and Feltham, namely C2v-symmetric, TBPY-5-type cations with two almost equally bonded nitrosyl ligands. In agreement with an 8 + 0 distribution of the relevant electrons, the formal [Ru0(NO+)2]2+ entities are found for L/X couples that donate more electron density on the central metal. Two solid compounds (8a/b, 12a/b) were found in both structures including the special case of the PiPr3/Br couple 12a/b, which led to crystals that contained both structure types in the same solid. Conversely, four compounds showed a single form in the solid but both forms in dichloromethane solution in terms of the solutions’ IR spectra. The irradiation of crystalline 12 with blue laser light resulted in the photoisomerisation of, mainly, the bent 1NO− ligand in terms of low-temperature IR spectroscopy.
Co-reporter:Martin Steinborn, Mihael Suhanji and Peter Klüfers
Dalton Transactions 2013 vol. 42(Issue 16) pp:5749-5754
Publication Date(Web):13 Feb 2013
DOI:10.1039/C3DT32901A
Sugar phosphates provide metal-binding sites both at their sugar core and at their phosphate group(s). Mixed sugar-core–phosphate chelation has been considered as a typical bonding mode within the physiological pH range for the central metabolite D-fructose 1,6-bisphosphate. The ReVO(tmen) metal fragment was used to enrich this coordination type. The formation of the [ReO(tmen)(Fruf2,3H−21,6P2H2-κ3O2,3,P1)]− monoanion was determined by NMR spectroscopy and mass spectrometry. The model compound rac-glycerol 1-phosphate yielded similar results in terms of NMR spectroscopy. Crystal-structure analyses of [ReO(tmen)(rac-Glyc2,3H−21PH-κ3O2,3,P)]·2H2O and [ReO(phen)(rac-Glyc2,3H−21PH-κ3O2,3,P)]·MeOH confirmed the coordination pattern.
Co-reporter:M.Sc. Xaver Wurzenberger;Christine Neumann ;Dr. Peter Klüfers
Angewandte Chemie 2013 Volume 125( Issue 19) pp:5264-5266
Publication Date(Web):
DOI:10.1002/ange.201300787
Co-reporter:M.Sc. Xaver Wurzenberger;Christine Neumann ;Dr. Peter Klüfers
Angewandte Chemie International Edition 2013 Volume 52( Issue 19) pp:5159-5161
Publication Date(Web):
DOI:10.1002/anie.201300787
Co-reporter:Dr. Thorsten Allscher ;Dr. Peter Klüfers
Chemistry - A European Journal 2012 Volume 18( Issue 34) pp:10571-10584
Publication Date(Web):
DOI:10.1002/chem.201100979
Abstract
Alditols (“sugar alcohols”, “glycitols”) form palladium(II) complexes in neutral aqueous solution if they can provide the threitol partial structure. This requirement excludes erythritol, ribitol, and allitol when applied to the common tetritols, pentitols, and hexitols. The remaining alditols are able to arrange their threo-tetraol-O4 pattern to an almost planar rhomb, to which four PdIIN2 (N2=bidentate nitrogen ligand) centres bind in a butterfly-shaped Pd4 motif. Bridging is the exclusive bonding mode of the four alkoxido donors. In contrast to the butterfly complexes, all alditols are able to form a species at a pH intermediate between neutrality and the stronger alkaline conditions of non-bridging diolato-palladium(II) binding, namely, the μ-triolato bonding mode. A Pd2(μ-triolato) unit shows the middle O atom of a propanetriolato fragment as a bridging ligator, with the lateral O atoms binding in the terminal mode.
Co-reporter:David Heß, Peter Klüfers
Carbohydrate Research 2011 Volume 346(Issue 13) pp:1752-1759
Publication Date(Web):27 September 2011
DOI:10.1016/j.carres.2011.05.031
Phenylboronic acid esters are formed by the three common 2-deoxy aldoses: 2-deoxy-d-erythro-pentose (‘2-deoxy-d-ribose’), 2-deoxy-d-lyxo-hexose (‘2-deoxy-d-galactose’), and 2-deoxy-d-arabino-hexose (‘2-deoxy-d-glucose’). The major species that was formed from equimolar quantities of boronic acid and the aldose, was the 3,4-monoester of the pentopyranose in a skew-boat conformation, and the 4,6-monoester in the case of the two hexopyranoses. A double molar quantity of boronic acid led, for both 2-deoxy-hexoses, to the diester of the open-chain aldehydo isomer as the major product: the 3,5:4,6-diester for the lyxo-configured deoxy-hexose, and the 3,4:5,6-diester of the arabino-configured isomer. Minor products of all reactions were identified by a combined NMR/DFT methodology.
Co-reporter:Johanna Schulten, Peter Klüfers
Carbohydrate Research 2011 Volume 346(Issue 13) pp:1767-1775
Publication Date(Web):27 September 2011
DOI:10.1016/j.carres.2011.05.035
Excess di(tert-butyl)silylene (DTBS) bis(trifluoromethanesulfonate) formed bis-DTBS derivatives with the four aldopentoses (arabinose, lyxose, ribose and xylose). The structure of the bis-chelates was affected by the bulk of the DTBS groups and the requirement of flat silacycles in the case of five-membered chelate rings. These restrictions resulted in unusual cyclic bis-chelates for ribofuranose (κO1,5,κO2,3 bis-chelate) and lyxopyranose (κO1,4,κO2,3 bis-chelate of a twisted boat conformation). Most importantly, all aldopentoses formed bis-chelates of their open-chain aldehydo isomers. The bis-chelates of aldehydo-arabinose and -xylose were κO2,3,κO4,5-bonded and thus exhibited five-membered chelate rings. The bis-chelates of aldehydo-lyxose and -ribose were κO2,4,κO3,5-bonded and resembled six-membered chelate rings. For lyxose, the aldehydo bis-chelate was isolated as a solid. The molecular structures were assigned by a combined 1H, 13C, and 29Si NMR spectroscopic approach, which was supported by X-ray analyses on crystals of the bis-DTBS chelates of κO1,2,κO3,5-bonded rac-xylofuranose, κO1,5,κO2,3-bonded d-ribofuranose, and κO2,4,κO3,5-bonded aldehydo-d-lyxose.
Co-reporter:Xaver Wurzenberger;Dr. Holger Piotrowski ;Dr. Peter Klüfers
Angewandte Chemie 2011 Volume 123( Issue 21) pp:5078-5082
Publication Date(Web):
DOI:10.1002/ange.201006898
Co-reporter:Philipp Grimminger and Peter Klüfers
Dalton Transactions 2010 vol. 39(Issue 3) pp:715-719
Publication Date(Web):13 Oct 2009
DOI:10.1039/B912603A
The reaction of the oxidorhenium(V) precursor [ReOCl3(PPh3)2] with the proteinogenic amino acid L-histidine (L-hisH) and the glycosides methyl α-D-mannopyranoside (Me-α-D-Manp) and methyl β-D-ribopyranoside (Me-β-D-Ribp) in methanol/triethylamine yielded the crystalline compounds [ReO(L-his)(Me-α-D-Manp2,3H−2)]·2MeOH (1) and [ReO(L-his)(Me-β-D-Ribp3,4H−2)]·½MeOH (2). The mixed-ligand complexes based on the ReVO moiety were characterised by single-crystal X-ray diffraction, NMR spectroscopy, elemental analysis and mass spectrometry. Both complexes are hydrolytically stable over prolonged periods of time and are accessible also by a purely aqueous route by replacing the rhenium(V) precursor with a perrhenate/reductant couple.
Co-reporter:Thomas Schwarz, David Heß and Peter Klüfers
Dalton Transactions 2010 vol. 39(Issue 23) pp:5544-5555
Publication Date(Web):11 May 2010
DOI:10.1039/C002711A
The chelating properties of the common aldohexoses D-glucose, D-mannose, and D-galactose are characteristically modified in 2-substituted derivatives. The 2-amino-2-deoxy-aldohexoses provide mono- and bis-metallisable anionic ligands after their reaction with metal probes of the PdIIN2 type (N2 = bidentate nitrogen ligand). The 2-amino function reliably participates in metal binding of the, mostly pyranoidic, carbohydrate chelators. Acetylation of the amino function yields the biologically important 2-N-acetylamino-2-deoxy-hexoses (GlcNAc, ManNAc, and GalNAc). On reaction with the palladium probe, the metal-binding properties of the deprotonated acetylamino function depends on the steric requirements introduced by the acetyl residue which is forced into a coplanar arrangement with the chelate ring. In the two 2-deoxy-aldohexoses, 2-deoxy-arabino-D-hexose (the 2-deoxy derivative of both D-glucose and D-mannose, ‘2-deoxy-glucose’) and 2-deoxy-lyxo-D-hexose (‘2-deoxy galactose’), the 2-position cannot contribute to metal binding. As a result, furanose-1,3 chelation becomes an important metal-binding mode. Due to the decreased acidity of the 2-deoxy-glycose's 1-hydroxy function, monometallation also takes place at the pyranose's 3,4-site.
Co-reporter:Natascha Ghaschghaie, Thomas Hoffmann, Martin Steinborn and Peter Klüfers
Dalton Transactions 2010 vol. 39(Issue 23) pp:5535-5543
Publication Date(Web):15 May 2010
DOI:10.1039/B925537K
CoIII(tacn) and GaIII(tacn) fragments (tacn = 1,4,7-triazacyclononane) are suitable metal probes for the detection of the tridentate chelating sites of a glycose. Three moles of hydroxide per mole of cobalt or gallium support triple deprotonation of the chelating triol functions at a glycose's backbone. The individual chelating sites are detected using 1D and 2D NMR techniques. The metal-binding sites always include the hydroxy function at the anomeric carbon atom. Chelators are derived from both the pyranose and the furanose isomers while forming five- and six-membered chelate rings by the use of cis,cis-1,2,3-triol functions. The assignment of less frequently occurring ligand isomers are supported by a DFT approach. Crystal-structure analysis on Na4[Cr(β-D-Manf1,2,3H−3)2]NO3·8.5H2O (Man = mannose) additionally upholds the NMR assignments.
Co-reporter:Thorsten Allscher, Yvonne Arendt, Peter Klüfers
Carbohydrate Research 2010 Volume 345(Issue 16) pp:2381-2389
Publication Date(Web):2 November 2010
DOI:10.1016/j.carres.2010.08.006
Four methyl d-pentopyranosides (β-Ara, α-Lyx, β-Rib, β-Xyl), as well as Me-β-l-Ara, some of them residing in a well-defined conformation in the solution state (Ara, Xyl) and some showing pronounced chair inversion in solution (Lyx, Rib), form bidentate chelates of the general formula [Pd(chxn)(LH−2)-κO,O′] and [Pd(tmen)(LH−2)-κO,O′], chxn = (R,R)-cyclohexane-1,2-diamine, tmen = N,N,N′,N′-ethane-1,2-diamine and L = glycoside, with PdIIN2-type metal probes. The dynamic behaviour of the free glycosides is maintained in their chelates, the only case where the metal is bonded by a cis-vicinal diol function. Thus, one fluctuating chelate was detected with the lyxopyranoside in the κO2,3 binding mode, and two fluctuating chelates were found for the ribopyranoside (κO2,3 and κO3,4). No fluctuating chelate was found for the arabinopyranoside (the free arabinopyranoside being non-fluctuating as well), or for the xylopyranoside (no cis-vicinal diol function). In addition, syn-diaxial chelation (κO2,4) was observed for the ribopyranoside and the xylopyranoside. The spectroscopic results were supplemented by X-ray analyses.Conformational fluctuation of a glycoside (methyl β-d-ribopyranoside in the scheme) is maintained on chelation with diamine-palladium(II) probes if, and only if, a cis-vicinal chelate such as the depicted κO2,3-bonded complex is formed. Both in trans-vicinal and syn-diaxial chelates, fluctuation is frozen and the sterically only possible conformer is enriched. The NMR investigation is based on the invention of ‘Pd-tmen’, a new coordinating cellulose solvent.
Co-reporter:Richard Betz ;Peter Klüfers
Inorganic Chemistry 2009 Volume 48(Issue 3) pp:925-935
Publication Date(Web):December 29, 2008
DOI:10.1021/ic8014018
A series of spiro-arsoranes bearing a phenyl moiety as the fifth substituent were synthesized applying open-chain, as well as cyclic vicinal diols, as chelating molecules by condensation reactions in aprotic solvents. The products synthesized are the spiro compounds of the general formula PhAs(DiolH−2)2 derived from the vicinal diols meso-2,3-butanediol, PhAs(meso-2,3-ButdH−2)2 (1), exo-cis-2,3-norbornanediol, PhAs{exo-cis-NobdH−2}2 (2), cis-1,2-cyclopentanediol, PhAs(cis-1,2-CptdH−2)2 (3), anhydroerythritol, PhAs(AnErytH−2)2 (4), cis-1,2-cyclohexanediol, PhAs(cis-1,2-ChxdH−2)2 (5), and rac-trans-1,2-cyclohexanediol, rac-{PhAs(trans-1,2-ChxdH−2)2} (6) which were identified as mononuclear compounds. A novel dimeric double-spiro environment for oxyarsoranes was found in the reaction products derived from the sterically demanding diols 1,1′-bicyclohexyl-1,1′-diol {PhAs(BhxdH−2)O}2 (7) and perfluorpinacol, {PhAs(FpinH−2)O}2 (8). The stability of the compounds in acidic and neutral aqueous media in the presence of organic co-solvents was investigated. A convenient synthetic procedure for spiro-oxyarsoranes, applying water as the solvent, was developed and proven to be advantageous. All of the compounds synthesized in this study were characterized by means of melting-point measurement, single-crystal X-ray analysis, NMR, IR, Raman, UV/vis, and mass spectrometry. The principles found for these reactions were valid for the methyl glycosides of β-d-ribofuranose and α-d-mannopyranose. The spiro-arsorane derived from methyl α-d-mannopyranoside, PhAs(Me-α-d-Manp2,3H−2)2 (9), is the first example of a structurally characterized carbohydrate-arsenic(V) compound.
Co-reporter:Kathrin Gilg, Tobias Mayer, Natascha Ghaschghaie and Peter Klüfers
Dalton Transactions 2009 (Issue 38) pp:7934-7945
Publication Date(Web):31 Jul 2009
DOI:10.1039/B909431H
In aqueous solution, the reducing sugar phosphates D-arabinose 5-phosphate, D-ribose 5-phosphate, D-fructose 1,6-bisphosphate, D-fructose 6-phosphate, D-glucose 6-phosphate and D-mannose 6-phosphate provide metal-binding sites at their glycose core on reaction with PdII(en) or MIII(tacn) residues (M = Ga, Co; en = ethylenediamine, tacn = 1,4,7-triazacyclononane). The individual species were detected by one- and two-dimensional NMR spectroscopy. The coordination patterns are related to the metal-binding modes of the respective parent glycoses. In detail, ribo- and arabinofuranose phosphate favour κO1,3 coordination, whereas the ketofuranose core of fructose phosphate and fructose bisphosphate provides the κO2,3 chelator thus maintaining the configuration of the respective major solution anomer. On palladium excess, D-fructose 6-phosphate is metallated twice in a unique κO1,3:κO2,4 metallation pattern. Dimetallation is also found for the aldohexose phosphates. A mixed glycose-core–phosphate chelation was detected for PdII(en) and MIII(tacn) residues with M = Al, Ga in the pH range just above the physiological pH for the D-fructose 1,6-bisphosphate ligand. The results are discussed in relation to D-fructose-1,6-bisphosphate-metabolism in class-II aldolases.
Co-reporter:Anna Zangl, Peter Klüfers, Dominik Schaniel and Theo Woike
Dalton Transactions 2009 (Issue 6) pp:1034-1045
Publication Date(Web):07 Jan 2009
DOI:10.1039/B812246F
Five novel complexes containing the {RuNO}6 fragment and the anions derived from L-histidine (L-his), rac-3-amino-alanine (rac-dap), kojic acid (koj), methyliminodiacetic acid (mida), and thiodiacetic acid (tda) have been synthesised and characterised by single-crystal X-ray diffraction analysis, mass spectrometry, spectroscopic methods (NMR, UV–vis, IR) and elemental analysis. In the irradiated complexes, [Ru(NO)Cl2(L-his)] (1), [Ru(NO)Cl2(rac-dap)] (2), K[Ru(NO)Cl3(koj)] (3), K[Ru(NO)Cl2(mida)]·½H2O (4), and K[Ru(NO)Cl2(tda)]·H2O (5), the existence of the photoinduced long-lived metastable isonitrosyl state S1 and/or the side-on-bonded S2 state were detected by differential scanning calorimetry (DSC) and/or IR spectroscopy. For all complexes 1–5 full geometry optimisation, frequency analysis and calculation of the isotropic magnetic shielding tensors have been conducted in the framework of DFT theory.
Co-reporter:Helene Giglmeier, Tobias Kerscher, Peter Klüfers, Dominik Schaniel and Theo Woike
Dalton Transactions 2009 (Issue 42) pp:9113-9116
Publication Date(Web):07 Sep 2009
DOI:10.1039/B912162E
Following photoexcitation at 80 K, two phenomena were detected on solid samples of a single substance, the tetraphenylborate of the [Ru(NO)(terpy)(L)]+ cation (terpy = 2,2′:6′,2″-terpyridine, L = glycolate(2−) [oxyacetate]): the formation of photoinduced linkage isomers of the nitrosyl ligand, and photorelease of nitric oxide. Populations of about 9% and 4% were measured for the photoinduced isonitrosyl (MS1) and the side-on nitrosyl (MS2) linkage isomers, respectively. At room temperature, NO release in the solid was observed as the only reaction.
Co-reporter:Yvonne Arendt, Oliver Labisch, Peter Klüfers
Carbohydrate Research 2009 Volume 344(Issue 10) pp:1213-1224
Publication Date(Web):6 July 2009
DOI:10.1016/j.carres.2009.04.008
The [PdII{(R,R)-chxn}(OH)2] reagent (chxn = 1,2-diaminocyclohexane) is introduced as a metal probe for the detection of the bidentate chelating sites of a glycose. Two moles of hydroxide per mole palladium support double deprotonation of potentially chelating diol functions at a glycose’s backbone. The individual chelating sites are detected using one- and two-dimensional NMR techniques. At equimolar amounts of palladium(II) and aldose, the metal-binding sites include mostly the hydroxy function at the anomeric carbon atom. Chelators are derived from both the pyranose and the furanose isomers. Most pyranose-based chelators form five-membered chelate rings by using their 1,2-diol function. Though 1,2-diolate bonding is also common to the furanoses, the formation of six-membered chelate rings by 1,3-bonding is more significant for them. Metal-excess conditions provoke mostly bis-bidentate 1,2;3,4-chelation but unusual isomers form also: thus d-xylose is dimetallated in its all-axial β-pyranose form, and erythrose’s dimetallation results in the formation of two isomers of a metal derivative of the open-chain hydrate. The spectroscopic results are supported by crystal-structure determinations on [Pd{(R,R)-chxn}(α-d-Xylp1,2H−2-κO1,2)]·H2O (Xyl = xylose), [Pd{(R,R)-chxn}(α-d-Ribp1,2H−2-κO1,2)]·2.25H2O (Rib = ribose), [Pd{(R,R)-chxn}(α-l-Thrf1,3H−2-κO1,3)]·2H2O (Thr = threose) and [Pd{(R,R)-chxn}(α-d-Eryf1,3H−2-κO1,3)]·3H2O (Ery = erythrose).A prominent metal-binding site in the aqueous solution equilibrium of an aldose is provided by the furanose isomer in its 1,3-bonding mode. Since this binding mode does not lead to typical signal patterns in NMR spectra, structural work on single crystals was necessary to confirm this form of aldose chelating. The figure shows l-threose adopting this mode, but pentoses and hexoses also ligate that way to palladium(II) centres. 1,3-Bonding galactofuranose thus is the major isomer in an equimolar aqueous solution of the palladium reagent [PdII{(R,R)-chxn}(OH)2] (chxn = 1,2-diaminocyclohexane) and d-galactose.
Co-reporter:Thorsten Allscher, Peter Klüfers
Carbohydrate Research 2009 Volume 344(Issue 4) pp:539-540
Publication Date(Web):10 March 2009
DOI:10.1016/j.carres.2008.12.001
The crystal structure of the first monosaccharide–metal complex ever reported, a β-d-lyxofuranose-bridged dimolybdate [Taylor, G. E.; Waters, J. M. Tetrahedron Lett.1981, 22, 1277–1278] was re-determined since the original work shows unbalanced charges, and thus an unclear protonation state of the lyxose ligand. As a result, the complex was found to be a monoanion whose charge is balanced by an ammonium counterion. The lyxose O5 atom is non-deprotonated, and the carbohydrate ligand is trianionic due to deprotonation of the O1, O2 and O3 hydroxy functions.Add an ammonium counterion and a proton to the lyxofuranose-O5. This recipe makes the missing charge balance of a 1981 structure determination vanish. The correction is desirable since the title compound pioneered the field of metal complexation by reducing sugars: its publication almost three decades ago marks the first structure determination on a crystalline metal complex of a glycose.
Co-reporter:Anna Zangl, Peter Klüfers, Dominik Schaniel, Theo Woike
Inorganic Chemistry Communications 2009 Volume 12(Issue 10) pp:1064-1066
Publication Date(Web):October 2009
DOI:10.1016/j.inoche.2009.08.021
The two novel binuclear pyrazole-3,5-dicarboxylato-bridged {RuNO}6 complexes K2[{Ru(NO)Cl}2(μ-pzdc)2] (1) and [{Ru(NO)(H2O)}2(μ-pzdc)2]·4H2O (2) (pzdc = pyrazole-3,5-dicarboxylate) were synthesized and characterized by elemental analysis, mass spectrometry and spectroscopic methods (NMR, UV–vis, IR). 2 was investigated by means of single-crystal X-ray diffraction analysis. On irradiation, in both 1 and 2 the existence of photoinduced long-lived metastable isonitrosyl states SI were detected by low-temperature infrared spectroscopy.The pyrazole-3,5-dicarboxylato ligand is able to bridge two {RuNO}6 centres to binuclear complexes. The figure shows the crystallographically characterised nitrosyl aqua complex. Metastable photoinduced linkage isomers were detected in both this aqua complex and its chlorido analogue by means of IR spectroscopy after laser irradiation at low temperatures.
Co-reporter:Peter Klüfers ;Moritz M. Reichvilser
European Journal of Inorganic Chemistry 2008 Volume 2008( Issue 3) pp:384-396
Publication Date(Web):
DOI:10.1002/ejic.200700837
Abstract
Cyclic selenites, of the general formula (DiolH–2)SeO, derived from the diols ethane-1,2-diol, propane-1,2-diol, cis-cyclopentane-1,2-diol, cis-cyclohexane-1,2-diol, trans-cyclohexane-1,2-diol, 1,1′-bicyclopentyl-1,1′-diol, 1,1′-bicyclohexyl-1,1′-diol, propane-1,3-diol, 2,2-dimethylpropane-1,3-diol, 1,1-bis(hydroxymethyl)cyclopropane, 1,1-bis(hydroxymethyl)cyclopentane, 1,4-anhydroerythritol and the methyl glycosides of β-D-ribofuranose, β-D-ribopyranose, α-D-mannopyranose, β-D-xylopyranose have been prepared and characterised by multinuclear NMR spectroscopy and single-crystal X-ray diffraction. Even with the polyfunctional sugar derivatives, oxidation of substrates did not occur. It has been demonstrated that the title compounds are hydrolytically stable at low pH values. Experimental NMR spectroscopy and structural data are consistent with results of density functional calculations and bonding has been analysed by means of natural bond orbital (NBO) theory.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Co-reporter:Thorsten Allscher;Xaver Kästele;Gerhard Kettenbach Dr.;Peter Klüfers Dr.;Thomas Kunte Dr.
Chemistry – An Asian Journal 2007 Volume 2(Issue 8) pp:1037-1045
Publication Date(Web):19 JUN 2007
DOI:10.1002/asia.200700094
The C4, C5, and C6 sugar alcohols erythritol (Eryt), D-threitol (D-Thre), D-arabitol (D-Arab), ribitol (Ribt), xylitol (Xylt), dulcitol (Dulc), and D-mannitol (D-Mann) form chelate complexes upon dissolution in Pd-en, an aqueous solution of [PdII(en)(OH)2]. Stability rules are derived from the proportion of a respective species in the solution equilibrium. Crystal-structure analysis supports the NMR spectroscopic results for a series of binuclear compounds that contain the sugar alcohols as tetraanionic polyolato ligands: [Pd2(en)2(ErytH−4)]⋅ 10H2O, [Pd2(en)2(D-Arab1,2;3,4H−4)]⋅ 7H2O, [Pd2(en)2(Xylt1,2;3,4H−4)]⋅4H2O, [Pd2(en)2(D-Mann1,2;3,4H−4)]⋅5H2O, and [Pd2(en)2(Dulc2,3;4,5H−4)]⋅6H2O. In the case of the pentitols and hexitols, the metalated tetraanions are stabilized by intramolecular hydrogen bonds. The hydrogen bonds uniformly connect an alkoxide acceptor to the hydroxy donor group located at the δ carbon atom. As a consequence of hydrogen bonding, the open-chain carbohydrate ligands become rigid. Crystal-structure analysis provides information on the configurational requirements for rigidity. According to these rules, the hydrogen-bond-supported Dulc2,3;4,5H−4 tetraanion provides a geometrically persistent ligating pattern. Intramolecular hydrogen bonding seems to be the most-competitive variable to metalation of a polyol. [Pd2(tm-2,1:3,2-tet)(OH)3]OH (tm-2,1:3,2-tet=1,3-bis(2′-dimethylaminoethyl)hexahydropyrimidine) is a metallizing agent that can force full metalation even in a case as intractable as that of dulcitol. Accordingly, [Pd4(tm-2,1:3,2-tet)2-(DulcH−6)]Cl2⋅16H2O contains the fully deprotonated hexitol as the ligand.
Co-reporter:Klaus Benner Dr.;Johannes Ihringer;Peter Klüfers Dr.;Danira Marinov Dr.
Angewandte Chemie International Edition 2006 Volume 45(Issue 35) pp:
Publication Date(Web):26 JUL 2006
DOI:10.1002/anie.200601162
Mining new assemblies: A molecular bucket wheel consisting of three β-cyclodextrin units, three tetrahedral tetraaqualithium cations, and a tetravalent metal center has been prepared (see picture). The assembly, held together by a series of hydrogen bonds, is also stable in solution.
Co-reporter:Matthias Hinrichs Dipl.-Chem.;Florian R. Hofbauer;Peter Klüfers Dr.
Chemistry - A European Journal 2006 Volume 12(Issue 17) pp:
Publication Date(Web):28 MAR 2006
DOI:10.1002/chem.200501567
With the [Re(CO)3Br3]2− ion as a precursor for the ReI(CO)3 fragment, the diols (1R,2R)-cyclohexane-1,2-diol [(1R,2R)-Chxd], anhydroerythritol (AnEryt), and (1S,2S)-cyclopentane-1,2-diol [(1S,2S)-Cptd] form dinuclear monoanions in the salts (NBu4)[(Re2(CO)6{μ-(1R,2R)-ChxdH−1}3] (1), [K([18]crown-6)][Re2(CO)6(μ-OMe)2(μ-AnErytH−1)] (2) and (NBu4)[Re2(CO)6{μ-(1S,2S)-CptdH−1}3] (3). The monoanionic diolato ligands in these triply bridged dirhenates(I) are monodentate. Bridging triolato ligation in the trirhenates(I) is supported by the anions of glycerol (Glyc) and methyl β-D-ribopyranoside (Me-β-D-Ribp), the latter binding in its 1C4 conformation, in (DBUH)2[Re3(CO)9(μ3-O)(μ3-GlycH−3)]⋅0.5 MeCN (4 a), (NEt4)[Re3(CO)9(μ3-OMe)(μ3-GlycH−3)] (4 b) and (DBUH)[Re3(CO)9(μ3-OMe)(μ3-1C4-Me-β-D-Ribp2,3,4H−3)] (5). The chiral sugar alcohols L-threitol (L-Thre) and D-arabitol (D-Arab) act as tetra- and pentadentate ligands, respectively, in (NEt4)[Re2(CO)6(L-ThreH−3)]⋅MeCN (6) and (NEt4)2(DBUH)2[Re6(CO)18(D-ArabH−5)2] (7). Complexes 6 and 7 are free of supporting oxo or methoxo ligands and use solely the O-atom pattern of the polyol for the connection of the ReI(CO)3 moieties.
Co-reporter:Xaver Kästele;Peter Klüfers Dr.;Reinhold Tacke Dr.
Angewandte Chemie International Edition 2006 Volume 45(Issue 20) pp:
Publication Date(Web):26 APR 2006
DOI:10.1002/anie.200503534
Contrary to a recent claim that the zwitterionic bis(diolato)silicate 1 exhibits remarkable hydrolytic stability at pH 7–8, a closer look at 29Si and 13C NMR spectroscopic data of 1 under various conditions (solvent, pH, concentration) reveals that hydrolysis products are the predominant species in solution.
Co-reporter:Klaus Benner Dr.;Johannes Ihringer;Peter Klüfers Dr.;Danira Marinov Dr.
Angewandte Chemie 2006 Volume 118(Issue 35) pp:
Publication Date(Web):26 JUL 2006
DOI:10.1002/ange.200601162
Neue selbstorganisierte Systeme: Ein molekulares Schaufelrad aus drei β-Cyclodextrin-Einheiten, drei tetraedrischen Tetraaqualithium-Kationen und einem vierwertigen Metallzentrum wurde synthetisiert (siehe Bild). Das Assoziat, das durch eine Reihe von Wasserstoffbrücken zusammengehalten wird, ist auch in Lösung stabil.
Co-reporter:Xaver Kästele;Peter Klüfers Dr.;Reinhold Tacke Dr.
Angewandte Chemie 2006 Volume 118(Issue 20) pp:
Publication Date(Web):26 APR 2006
DOI:10.1002/ange.200503534
Anders als kürzlich behauptet ist das zwitterionische Bis(diolato)silicat 1 bei pH 7–8 nicht erstaunlich hydrolysestabil. Dies ergab eine genauere Analyse der 29Si- und 13C-NMR-spektroskopischen Daten von 1 unter einer Vielzahl unterschiedlicher Bedingungen (Lösungsmittel, pH, Konzentration), nach der in Lösung vor allem Hydrolyseprodukte vorliegen.
Co-reporter:Michael Barth;Xaver Kästele;Peter Klüfers
European Journal of Inorganic Chemistry 2005 Volume 2005(Issue 7) pp:
Publication Date(Web):7 APR 2005
DOI:10.1002/ejic.200300925
[mer-(dien)(NO)Ru(AnErytH–2)]BPh4·2 H2O (1), [mer-(dien)(NO)Ru(R,R-ChxdH–2)]BPh4 (2), [mer-(dien)(NO)Ru(EthdH–2)]BPh4 (3), and [mer-(dien)(NO)Ru(Me-β-D-Ribf2,3H–2)]BPh4·5.5 H2O (4) have been synthesized in the form of light pink crystals by the reaction of [mer-(dien)(NO)RuCl2]X with the respective diol in aqueous sodium hydroxide solution (dien = diethylenetriamine, AnEryt = anhydroerythritol, Chxd = cyclohexane-1,2-diol, Ethd = ethanediol, Rib = ribose; X = BPh4 or PF6). The nitrosyl ligand exhibits a strong trans influence which causes the trans-bonded oxygen atom of the diolato ligand to form a shorter bond with the Ru centre. Mean values are 2.038 for cis and 1.946 Å for transO-binding. Back donation is strongly supported by the diolato ligand resulting in low energies for the N–O stretch which can be observed as low as 1805 cm–1. trans-Oxygen atoms do not act as hydrogen-bond acceptors in any of the cases. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Co-reporter:Xaver Kästele;Peter Klüfers Dr.;Florian Kopp Dipl.-Chem.;Jörg Schuhmacher Dr.;Martin Vogt Dr.
Chemistry - A European Journal 2005 Volume 11(Issue 21) pp:
Publication Date(Web):3 AUG 2005
DOI:10.1002/chem.200500147
Anhydroerythritol (AnEryt) shares some of its ligand properties with furanosides and furanoses. Its bonding to silicon centers of coordination number four, five, and six was studied by X-ray and NMR methods, and compared to silicon bonding of related compounds. Diphenyl(cycloalkylenedioxy)silanes show various degrees of oligomerization depending on the diol component involved. For example, Ph2Si(cis-ChxdH−2) (1) and Ph2Si{(R,R)-trans-ChxdH−2)} (2; Chxd=cyclohexanediol) are dimeric, Ph2Si(AnErytH−2) (3) is monomeric, and Ph2Si(L-AnThreH−2) (4; AnThre=anhydrothreitol) is trimeric both in the solid state and in solution. Ph2Si(cis-CptdH−2) (5) (Cptd=cyclopentanediol) is monomeric in solution but dimerizes on crystallization. Si(AnErytH−2)2 (6) and Si(cis-CptdH−2)2 (7) are monomeric spiro compounds in solution but are pentacoordinate dimers in the crystalline state. Pentacoordinate silicate ions are found in A[Si(OH)(AnErytH−2)2] (A=Na, 8 a; Rb, 8 b; Cs, 8 c). Related compounds are formed by substitution of the hydroxo by a phenyl ligand. K[SiPh(AnErytH−2)2]⋅1/2 MeOH (9) is a prototypical example as it shows the two most significant isomers in one crystal structure: the syn/anti and the anti/anti form (syn and anti define the oxolane ring orientation close to, or apart from, the monodentate ligand, respectively). syn/anti Isomerism generally rules the appearance of the NMR spectra of pentacoordinate silicates of furanos(id)e ligands. NMR spectroscopic data are presented for various pentacoordinate bis(diolato)silicates of adenosine, cytidine, methyl-β-D-ribofuranoside, and ribose. In even more basic solutions, hexacoordinate silicates are enriched. Preliminary X-ray analyses are presented for Cs2[Si(CydH−2)3]⋅ 21.5 H2O (10) and Cs2[Si(cis-InsH−3)]⋅ cis-Ins⋅8 H2O (11) (Cyd=cytidine, Ins=inositol).
Co-reporter:Andreas Geißelmann Dr.;Peter Klüfers Dr.;Claudia Kropfgans Dr.;Peter Mayer Dr.;Holger Piotrowski Dr.
Angewandte Chemie 2005 Volume 117(Issue 6) pp:
Publication Date(Web):3 JAN 2005
DOI:10.1002/ange.200460079
Cyclodextrinliganden: Kohlenhydrate eignen sich als Gerüstmoleküle mit einem Muster aus metallbindenden Sauerstoffatomen. Die zweiwertigen Formen der biologisch wichtigen Metalle Eisen und Mangan können Teil solcher Assoziate sein (siehe Struktur; blau Fe, rot O, grün Gegenion, gelb H-Brücken zwischen Wassermolekülen). Die Assoziate werden durch günstige Beiträge, die nicht aus der Kohlenhydrat-Metall-Wechselwirkung resultieren, stabilisiert.
Co-reporter:Andreas Geißelmann Dr.;Peter Klüfers Dr.;Claudia Kropfgans Dr.;Peter Mayer Dr.;Holger Piotrowski Dr.
Angewandte Chemie International Edition 2005 Volume 44(Issue 6) pp:
Publication Date(Web):3 JAN 2005
DOI:10.1002/anie.200460079
Cyclodextrin ligands: Carbohydrates can be used as framework molecules that provide patterns of metal-binding oxygen atoms. The divalent forms of the biologically important metals iron and manganese can be part of such assemblies (see structure: Fe blue, O red, counterion green, hydrogen bonds between water molecules yellow). The assemblies are stabilized by favorable contributions other than the carbohydrate–metal interaction.
Co-reporter:Peter Klüfers Dr.;Florian Kopp Dipl.-Chem.;Martin Vogt Dr.
Chemistry - A European Journal 2004 Volume 10(Issue 18) pp:
Publication Date(Web):29 JUL 2004
DOI:10.1002/chem.200306059
Five-coordinate phenylsilicates are formed from the reaction of trimethoxy(phenyl)silane with monosaccharides in methanol in the presence of a stoichiometric amount of base. Five complexes have been isolated and characterized with two ketoses and three aldopentoses. The silicon central atom in [K([18]crown-6)][PhSi(β-D-Fruf 2,3H−2)2]⋅MeOH (1, Fru=fructose) is part of two chelate rings, with the ligands being β-D-fructofuranose-O 2,O 3 dianions. The β-furanose isomer is best suited for silicon ligation because it exhibits a torsion angle close to 0° for the most acidic diol function, thus assuring a flat chelate ring. The same structural principles are also found in [K([18]crown-6)][PhSi(β-D-Araf1,2H−2)2]⋅2 MeOH (2, Ara=arabinose), [K([18]crown-6)][PhSi(α-D-Ribf1,2H−2)2] (3, Rib=ribose), [K([18]crown-6)][PhSi(α-D-Xylf1,2H−2)2]⋅ acetone (4, Xyl=xylose), and [K([18]crown-6)][PhSi(α-D-Rulf2,3H−2)2] (5, Rul=ribulose).
Co-reporter:Peter Klüfers Dr.;Thomas Kunte Dr.
Chemistry - A European Journal 2003 Volume 9(Issue 9) pp:
Publication Date(Web):5 MAY 2003
DOI:10.1002/chem.200204342
The cellulose solvent Pd-en, an aqueous solution of [(en)PdII(OH)2] (en=ethylenediamine), reacts with the monosaccharides D-arabinose (D-Ara), D-ribose (D-Rib), rac-mannose (rac-Man), and D-galactose (D-Gal) under formation of dimetalated aldose complexes, if the molar ratio of Pd and sugar is 2:1 or larger. In the Pd2 complexes, the aldoses are tetra-deprotonated and act as bisdiolato ligands. Two crystalline pentose complexes were isolated: [(en)2Pd2(β-D-Arap1,2,3,4 H−4)]⋅5 H2O (1) and [(en)2Pd2(β-D-Ribp1,2,3,4 H−4)]⋅6.5 H2O (2), along with two hexose complexes. With rac-Man, the major solution species is crystallized as the 9.4-hydrate [(en)2Pd2(β-rac-Manp1,2,3,4 H−4)]⋅9.4 H2O (3). From the respective D-Gal solutions, [(en)2Pd2(β-D-Galf1,3,5,6 H−4)]⋅5 H2O⋅C2H5OH (4), with the sugar tetraanion in its furanose form, is crystallized though it is not the major species, rather the second most abundant in purely aqueous solutions. The Galf species is enriched in the mother liquors to the extent of 25 % of total sugar content. Substitution of the en ligand by two molecules of ammonia, methylamine, or isopropylamine, respectively, results in the formation of different solution species. With the bulkiest ligand, isopropylamine, monometalation of the aldoses in the 1,2-position is exclusively observed.
Co-reporter:Klaus Benner Dr.;Peter Klüfers Dr.;Martin Vogt Dipl.-Chem.
Angewandte Chemie International Edition 2003 Volume 42(Issue 9) pp:
Publication Date(Web):26 FEB 2003
DOI:10.1002/anie.200390274
Building bridges: Fumed colloidal silica can be dissolved in alkaline aqueous solutions of the open-chain sugar alcohols mannitol, xylitol, and threitol. These polyols are able to form six-coordinate silicon complexes that are stabilized by intramolecular hydrogen bonds. The prototypical core is shown (yellow bars: the intramolecular H bonds).
Co-reporter:Peter Klüfers;Oswald Krotz;Martin Oßberger
European Journal of Inorganic Chemistry 2002 Volume 2002(Issue 8) pp:
Publication Date(Web):2 JUL 2002
DOI:10.1002/1099-0682(200208)2002:8<1919::AID-EJIC1919>3.0.CO;2-6
The reaction of anhydroerythritol (AnEryt) and methyl-β-D-galactopyranoside (Me-β-D-Galp) with dichloro[hydridotris(pyrazolyl)borato]oxorhenium(V) [(tpb)ReOCl2] in methanol/triethylamine results in the formation of blue crystals of the diolato complexes [(tpb)ReO(AnErytH−2)] (1) and [(tpb)ReO(Me-β-D-Galp3,4H−2)] (2). The amounts of anti-1 and syn-1 isomers are investigated by means of NMR spectroscopy and depend on the solvent chosen. For 2, the generally rigid pyranoside ligand enters the complex in a conformation that is even more heavily strained than the corresponding isopropylidene sugar in terms of torsion angles. Though anti and syn isomers are also formed in non-aqueous media initially, various synthetic procedures are given to obtain pure syn-2. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
Co-reporter:Peter Klüfers;Thomas Kunte
European Journal of Inorganic Chemistry 2002 Volume 2002(Issue 6) pp:
Publication Date(Web):25 APR 2002
DOI:10.1002/1099-0682(200206)2002:6<1285::AID-EJIC1285>3.0.CO;2-T
The reaction of the reducing aldopentose lyxose towards the metal centres in the copper-based cellulose solvents Schweizer’s reagent (cupric hydroxide in aqueous ammonia) and Cu-en (cupric hydroxide in aqueous ethylenediamine) was investigated. Crystals of the trinuclear complexes [(NH3)4CuII3(β-D-Lyxp1,2,3H−3)2(H2O)2]·4H2O (1) and [(en)2CuII3(β-D-Lyxp1,2,3H−3)2(H2O)2]·4H2O (2) (Lyxp = lyxopyranose) were grown upon preventing Fehling-type aldose oxidation. One of the three cupric centres is coordinated by two chelating diolato ligands only, hence both ammonia and ethylenediamine are displaced from CuII by a carbohydrate ligand. A binuclear lyxose-palladium(II) complex is formed on reaction of lyxose with Pd-en ([(en)Pd(OH)2] in water), which is another cellulose solvent of the coordinating type. From racemic mixtures of the lyxose enantiomers, crystals of [(en)2PdII2(β-rac-LyxpH−4)]·7H2O (3) were obtained. 13C NMR spectra reveal the bimetallated lyxose tetraanions to be the main species in palladium-rich solutions. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
Co-reporter:Peter Klüfers Dr.;Thomas Kunte Dipl.-Chem.
Angewandte Chemie International Edition 2001 Volume 40(Issue 22) pp:
Publication Date(Web):16 NOV 2001
DOI:10.1002/1521-3773(20011119)40:22<4210::AID-ANIE4210>3.0.CO;2-Z
The most important monosaccharide—and not a single structurally characterized transition metal complex. That is the actual situation regarding basis data for understanding or designing metal-catalyzed reactions of D-glucose. This oversight is remedied with a palladium(II) complex and a structural analysis (see picture, en=ethylenediamine).
Co-reporter:Peter Klüfers Dr.;Thomas Kunte Dipl.-Chem.
Angewandte Chemie 2001 Volume 113(Issue 22) pp:
Publication Date(Web):15 NOV 2001
DOI:10.1002/1521-3757(20011119)113:22<4356::AID-ANGE4356>3.0.CO;2-W
Das wichtigste Monosaccharid – und nicht ein einziger strukturell aufgeklärter Übergangsmetallkomplex! Dies beschreibt die Verfügbarkeit von Basisdaten, wenn metallkatalysierte Reaktionen mit D-Glucose verstanden oder neu entworfen werden sollen. Mit dem Palladium(II)-Komplex (siehe Abbildung, en=Ethylendiamin) liegt nun eine erste Strukturanalyse vor.
Co-reporter:Kathrin Gilg, Tobias Mayer, Natascha Ghaschghaie and Peter Klüfers
Dalton Transactions 2009(Issue 38) pp:NaN7945-7945
Publication Date(Web):2009/07/31
DOI:10.1039/B909431H
In aqueous solution, the reducing sugar phosphates D-arabinose 5-phosphate, D-ribose 5-phosphate, D-fructose 1,6-bisphosphate, D-fructose 6-phosphate, D-glucose 6-phosphate and D-mannose 6-phosphate provide metal-binding sites at their glycose core on reaction with PdII(en) or MIII(tacn) residues (M = Ga, Co; en = ethylenediamine, tacn = 1,4,7-triazacyclononane). The individual species were detected by one- and two-dimensional NMR spectroscopy. The coordination patterns are related to the metal-binding modes of the respective parent glycoses. In detail, ribo- and arabinofuranose phosphate favour κO1,3 coordination, whereas the ketofuranose core of fructose phosphate and fructose bisphosphate provides the κO2,3 chelator thus maintaining the configuration of the respective major solution anomer. On palladium excess, D-fructose 6-phosphate is metallated twice in a unique κO1,3:κO2,4 metallation pattern. Dimetallation is also found for the aldohexose phosphates. A mixed glycose-core–phosphate chelation was detected for PdII(en) and MIII(tacn) residues with M = Al, Ga in the pH range just above the physiological pH for the D-fructose 1,6-bisphosphate ligand. The results are discussed in relation to D-fructose-1,6-bisphosphate-metabolism in class-II aldolases.
Co-reporter:Anna Zangl, Peter Klüfers, Dominik Schaniel and Theo Woike
Dalton Transactions 2009(Issue 6) pp:NaN1045-1045
Publication Date(Web):2009/01/07
DOI:10.1039/B812246F
Five novel complexes containing the {RuNO}6 fragment and the anions derived from L-histidine (L-his), rac-3-amino-alanine (rac-dap), kojic acid (koj), methyliminodiacetic acid (mida), and thiodiacetic acid (tda) have been synthesised and characterised by single-crystal X-ray diffraction analysis, mass spectrometry, spectroscopic methods (NMR, UV–vis, IR) and elemental analysis. In the irradiated complexes, [Ru(NO)Cl2(L-his)] (1), [Ru(NO)Cl2(rac-dap)] (2), K[Ru(NO)Cl3(koj)] (3), K[Ru(NO)Cl2(mida)]·½H2O (4), and K[Ru(NO)Cl2(tda)]·H2O (5), the existence of the photoinduced long-lived metastable isonitrosyl state S1 and/or the side-on-bonded S2 state were detected by differential scanning calorimetry (DSC) and/or IR spectroscopy. For all complexes 1–5 full geometry optimisation, frequency analysis and calculation of the isotropic magnetic shielding tensors have been conducted in the framework of DFT theory.
Co-reporter:Helene Giglmeier, Tobias Kerscher, Peter Klüfers, Dominik Schaniel and Theo Woike
Dalton Transactions 2009(Issue 42) pp:NaN9116-9116
Publication Date(Web):2009/09/07
DOI:10.1039/B912162E
Following photoexcitation at 80 K, two phenomena were detected on solid samples of a single substance, the tetraphenylborate of the [Ru(NO)(terpy)(L)]+ cation (terpy = 2,2′:6′,2″-terpyridine, L = glycolate(2−) [oxyacetate]): the formation of photoinduced linkage isomers of the nitrosyl ligand, and photorelease of nitric oxide. Populations of about 9% and 4% were measured for the photoinduced isonitrosyl (MS1) and the side-on nitrosyl (MS2) linkage isomers, respectively. At room temperature, NO release in the solid was observed as the only reaction.
Co-reporter:Thomas Schwarz, David Heß and Peter Klüfers
Dalton Transactions 2010 - vol. 39(Issue 23) pp:NaN5555-5555
Publication Date(Web):2010/05/11
DOI:10.1039/C002711A
The chelating properties of the common aldohexoses D-glucose, D-mannose, and D-galactose are characteristically modified in 2-substituted derivatives. The 2-amino-2-deoxy-aldohexoses provide mono- and bis-metallisable anionic ligands after their reaction with metal probes of the PdIIN2 type (N2 = bidentate nitrogen ligand). The 2-amino function reliably participates in metal binding of the, mostly pyranoidic, carbohydrate chelators. Acetylation of the amino function yields the biologically important 2-N-acetylamino-2-deoxy-hexoses (GlcNAc, ManNAc, and GalNAc). On reaction with the palladium probe, the metal-binding properties of the deprotonated acetylamino function depends on the steric requirements introduced by the acetyl residue which is forced into a coplanar arrangement with the chelate ring. In the two 2-deoxy-aldohexoses, 2-deoxy-arabino-D-hexose (the 2-deoxy derivative of both D-glucose and D-mannose, ‘2-deoxy-glucose’) and 2-deoxy-lyxo-D-hexose (‘2-deoxy galactose’), the 2-position cannot contribute to metal binding. As a result, furanose-1,3 chelation becomes an important metal-binding mode. Due to the decreased acidity of the 2-deoxy-glycose's 1-hydroxy function, monometallation also takes place at the pyranose's 3,4-site.
Co-reporter:Natascha Ghaschghaie, Thomas Hoffmann, Martin Steinborn and Peter Klüfers
Dalton Transactions 2010 - vol. 39(Issue 23) pp:NaN5543-5543
Publication Date(Web):2010/05/15
DOI:10.1039/B925537K
CoIII(tacn) and GaIII(tacn) fragments (tacn = 1,4,7-triazacyclononane) are suitable metal probes for the detection of the tridentate chelating sites of a glycose. Three moles of hydroxide per mole of cobalt or gallium support triple deprotonation of the chelating triol functions at a glycose's backbone. The individual chelating sites are detected using 1D and 2D NMR techniques. The metal-binding sites always include the hydroxy function at the anomeric carbon atom. Chelators are derived from both the pyranose and the furanose isomers while forming five- and six-membered chelate rings by the use of cis,cis-1,2,3-triol functions. The assignment of less frequently occurring ligand isomers are supported by a DFT approach. Crystal-structure analysis on Na4[Cr(β-D-Manf1,2,3H−3)2]NO3·8.5H2O (Man = mannose) additionally upholds the NMR assignments.
Co-reporter:Martin Steinborn, Mihael Suhanji and Peter Klüfers
Dalton Transactions 2013 - vol. 42(Issue 16) pp:NaN5754-5754
Publication Date(Web):2013/02/13
DOI:10.1039/C3DT32901A
Sugar phosphates provide metal-binding sites both at their sugar core and at their phosphate group(s). Mixed sugar-core–phosphate chelation has been considered as a typical bonding mode within the physiological pH range for the central metabolite D-fructose 1,6-bisphosphate. The ReVO(tmen) metal fragment was used to enrich this coordination type. The formation of the [ReO(tmen)(Fruf2,3H−21,6P2H2-κ3O2,3,P1)]− monoanion was determined by NMR spectroscopy and mass spectrometry. The model compound rac-glycerol 1-phosphate yielded similar results in terms of NMR spectroscopy. Crystal-structure analyses of [ReO(tmen)(rac-Glyc2,3H−21PH-κ3O2,3,P)]·2H2O and [ReO(phen)(rac-Glyc2,3H−21PH-κ3O2,3,P)]·MeOH confirmed the coordination pattern.
Co-reporter:Anna K. E. Gallien, Dominik Schaniel, Theo Woike and Peter Klüfers
Dalton Transactions 2014 - vol. 43(Issue 35) pp:NaN13292-13292
Publication Date(Web):2014/07/14
DOI:10.1039/C4DT01506A
Two different structure types were found for a series of mononuclear dinitrosyl complexes of the general formula [RuL2(NO)2X]BF4 (L = monodentate phosphane, X = Cl, Br, I). The {Ru(NO)2}8-type target compounds were prepared by the reduction of the respective {RuNO}6 precursors and subsequent oxidative addition of (NO)BF4. About one half of the new compounds share their molecular structure with the hitherto only representative of this class of dinitrosyls, Pierpont and Eisenberg's [RuCl(NO)2(PPh3)2]PF6·C6H6 (Inorg. Chem., 1972, 11, 1088–1094). The Cs-symmetric cations exhibit both a linear and a bent Ru–N–O fragment, in line with a formal 6 + 2 split of the {Ru(NO)2}8 electron sum in the sense of a [RuII(NO+)(1NO−)]2+ bonding. The coordination entity's configuration in this subgroup is described by IUPAC's polyhedral symbol SPY-5. Continuous shape measures (CShM) as defined by Alvarez et al. (Coord. Chem. Rev., 2005, 249, 1693–1708) reveal a uniform deviation from the L–M–L angles expected for SPY-5, in a narrower sense, towards a vacant octahedron (vOC-5). DFT calculations confirmed that Enemark and Feltham's analysis (Coord. Chem. Rev., 1974, 13, 339–406) of the electronic situation of the {Ru(NO)2}8 group remains adequate. The same holds for the second subclass of new compounds the existence of which had been predicted in the same paper by Enemark and Feltham, namely C2v-symmetric, TBPY-5-type cations with two almost equally bonded nitrosyl ligands. In agreement with an 8 + 0 distribution of the relevant electrons, the formal [Ru0(NO+)2]2+ entities are found for L/X couples that donate more electron density on the central metal. Two solid compounds (8a/b, 12a/b) were found in both structures including the special case of the PiPr3/Br couple 12a/b, which led to crystals that contained both structure types in the same solid. Conversely, four compounds showed a single form in the solid but both forms in dichloromethane solution in terms of the solutions’ IR spectra. The irradiation of crystalline 12 with blue laser light resulted in the photoisomerisation of, mainly, the bent 1NO− ligand in terms of low-temperature IR spectroscopy.
Co-reporter:Philipp Grimminger and Peter Klüfers
Dalton Transactions 2010 - vol. 39(Issue 3) pp:NaN719-719
Publication Date(Web):2009/10/13
DOI:10.1039/B912603A
The reaction of the oxidorhenium(V) precursor [ReOCl3(PPh3)2] with the proteinogenic amino acid L-histidine (L-hisH) and the glycosides methyl α-D-mannopyranoside (Me-α-D-Manp) and methyl β-D-ribopyranoside (Me-β-D-Ribp) in methanol/triethylamine yielded the crystalline compounds [ReO(L-his)(Me-α-D-Manp2,3H−2)]·2MeOH (1) and [ReO(L-his)(Me-β-D-Ribp3,4H−2)]·½MeOH (2). The mixed-ligand complexes based on the ReVO moiety were characterised by single-crystal X-ray diffraction, NMR spectroscopy, elemental analysis and mass spectrometry. Both complexes are hydrolytically stable over prolonged periods of time and are accessible also by a purely aqueous route by replacing the rhenium(V) precursor with a perrhenate/reductant couple.
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