Naturally occurring polymers are promising biocompatible materials that have many applications for emerging therapies, drug delivery systems, and diagnostic agents. The handling and processing of such materials still constitutes a major challenge, which can limit the full exploitation of their properties. This study explores an ambient environment processing technique: coaxial electrospray (CO-ES) to encapsulate genistein (an isoflavonoid and model drug), superparamagnetic iron oxide nanoparticles (SPIONs, 10–15 nm), and a fluorophore (BODIPY) into a layered (triglyceride tristearin shell) particulate system, with a view to constructing a theranostic agent. Mode mapping of CO-ES led to an optimized atomization engineering window for stable jetting, leading to encapsulation of SPIONs within particles of diameter 0.65–1.2 μm and drug encapsulation efficiencies of around 92%. Electron microscopy was used to image the encapsulated SPIONs and confirm core–shell triglyceride encapsulation in addition to further physicochemical characterization (AFM, FTIR, DSC, and TGA). Cell viability assays (MTT, HeLa cells) were used to determine optimal SPION loaded particles (∼1 mg/mL), while in vitro release profile experiments (PBS, pH = 7.4) demonstrate a triphasic release profile. Further cell studies confirmed cell uptake and internalization at selected time points (t = 1, 2, and 4 h). The results suggest potential for using the CO-ES technique as an efficient way to encapsulate SPIONs together with sensitive drugs for the development of multimodal particles that have potential application for combined imaging and therapy.Keywords: drug delivery; electrospraying; encapsulation; imaging; nanoparticle; theranostics;

The catalytic activity of a series of neutral and cationic, homo- and heteroleptic, mono- and bimetallic palladium(II) compounds based on dithiocarbamate and dithiooxamide S,S-donor ligands is described. High activity was observed in the regio- and chemo-selective C–H functionalization of benzo[h]quinoline to 10-alkoxybenzo[h]quinoline and 8-methylquinoline to 8-(methoxymethyl)quinoline in the presence of the oxidant PhI(OAc)2. The best performance was found for [Pd(Me2dazdt)2]I6 (Me2dazdt = N,N′-dimethyl-perhydrodiazepine-2,3-dithione), [PdI2(Me2dazdt)] and [Pd(Cy2DTO)2]I8 (Cy2DTO = N,N′-dicyclohexyl-dithiooxamide) which are all obtained directly as products of sustainable Pd-metal leaching processes used to recover palladium from scrap metal. These compounds provided almost quantitative yields under milder conditions (50 °C, 1–3 mol% Pd loading) and much shorter reaction times (1–3 h) than reported previously. These results illustrate how the complexes obtained from the selective and sustainable recovery of Pd from automotive heterogeneous Three Way Catalysts (TWC) can be employed directly in homogeneous catalysis, avoiding further metal recovery steps and valorising the metal complex itself in a ‘circular economy’ model.

The versatile rhenium complex [ReCl(CO)3(bpyCCH)] (HCCbpy = 5-ethynyl-2,2′-bipyridine) is used to generate a series of bimetallic complexes through the hydrometallation of [MHCl(CO)(BTD)(PPh3)2] (M = Ru, Os; BTD = 2,1,3-benzothiadiazole). The ruthenium complex [Ru{CHCH-bpyReCl(CO)3}Cl(BTD)(CO)(PPh3)2] was characterised structurally. Ligand exchange reactions with bifunctional linkers bearing oxygen and sulfur donors provide access to tetra- and pentametallic complexes such as [{M{CHCH-bpyReCl(CO)3}(CO)(PPh3)2}2(S2CNC4H8NCS2)] and Fe[C5H4CO2M{CHCH-bpyReCl(CO)3}(CO)(PPh3)2]2. The effect of the group 8 metal on the photophysical properties of the rhenium centre was investigated using the complexes [Ru{CHCH-bpyReCl(CO)3}Cl(BTD)(CO)(PPh3)2] and [M{CHCH-bpyReCl(CO)3}{S2P(OEt)2}(CO)(PPh3)2] (M = Ru, Os). This revealed the quenching of the rhenium-based emission in favour of weak radiative processes based on the Ru and Os centres. The potential for exploiting this effect is illustrated by the reaction of [Ru{CHCH-bpyReCl(CO)3}Cl(CO)(BTD)(PPh3)2] with carbon monoxide, which results in a 5-fold fluorescence enhancement in the dicarbonyl product, [Ru{CHCH-bpyReCl(CO)3}Cl(CO)2(PPh3)2], as the quenching effect is disrupted.

The sensing of carbon monoxide (CO) using electrochemical cells or semiconducting metal oxides has led to inexpensive alarms for the home and workplace. It is now recognised that chronic exposure to low levels of CO also poses a significant health risk. It is perhaps surprising therefore that the CO is used in cell-signalling pathways and plays a growing role in therapy. However, the selective monitoring of low levels of CO remains challenging, and it is this area that has benefited from the development of probes which give a colour or fluorescence response. This feature article covers the design of chromo-fluorogenic probes and their application to CO sensing in air, solution and in cells.

The disulfide ligand (SC6H4CO2H-4)2 acts as a simple but versatile linker for a range of group 8 transition metals through reaction of the oxygen donors. This leads to a range of homobimetallic ruthenium and osmium alkenyl compounds, [{M(CH═CHR)(CO)(PPh3)2(O2CC6H4S-4)}2] (M = Ru, Os; R = C6H4Me-4). Additional metal-based functionality can be added through the use of precursors incorporating rhenium bipyridine units (R = (bpy)ReCl(CO)3). The more robust diphosphine ligands in [{Ru(dppm)2(O2CC6H4S-4)}2]2+ (dppm = diphenylphosphinomethane) allow reduction of the disulfide bond with sodium borohydride to yield the thiol complex [Ru(O2CC6H4SH-4)(dppm)2]+. This complex reacts with [AuCl(PPh3)] to afford the bimetallic compound [Ru(dppm)2(O2CC6H4S-4)Au(PPh3)]+. However, an improved route to the same and related heterobimetallic compounds is provided by the reaction of cis-[RuCl2(dppm)2] with [Au(SC6H4CO2H-4)(L)] (L = PPh3, PCy3, PMe3, IDip) in the presence of base and NH4PF6 (IDip = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). The heterotrimetallic compound [Au(SC6H4CO2Ru(dppm)2)2]+ is accessible through the reaction of the homoleptic gold(I) dithiolate [Au(SC6H4CO2H-4)2]PPN (PPN = bis(triphenylphosphine)iminium) with cis-[RuCl2(dppm)2]. Without departure from the same methodology, greater complexity can be incorporated into the system to provide the penta- and heptametallic assemblies [(dppf){AuSC6H4CO2Ru(dppm)2}2]2+ and [(dppf){AuSC6H4CO2Os(CH═CH-bpyReCl(CO)3)(CO)(PPh3)2}2]. The same stepwise approach provides the dinuclear organometallic complexes [(L)Au(SC6H4CO2-4)M(CH═CHC6H4Me-4)(CO)(PPh3)2] (M = Ru, Os; L = PPh3, IDip). Complexes containing three metals from different groups of the periodic table [(L)Au(SC6H4CO2-4)M{CH═CH-bpyReCl(CO)3}(CO)(PPh3)2] (M = Ru, Os) can also be prepared, with one ruthenium example (L = PPh3) being structurally characterized. In order to illustrate the versatility of this approach, the synthesis and characterization (IR and NMR spectroscopy, TEM, EDS, and TGA) of the functionalized gold and palladium nanoparticles Au@[SC6H4CO2Ru(dppm)2]+ and Pd@[SC6H4CO2Ru(dppm)2]+ is reported.

The HCl salt of the aminodiphosphine ligand HN(CH2CH2PPh2)2 reacts with [M(CO)4(pip)2] (M = Mo, W; pip = piperidine) to yield [M{κ2-HN(CH2CH2PPh2)2}(CO)4]. The molybdenum analogue readily loses a carbonyl ligand to form [Mo{κ3-HN(CH2CH2PPh2)2}(CO)3], which was structurally characterized. The same ligand backbone is used to form the new bifunctional ligand, KS2CN(CH2CH2PPh2)2, which reacts with nickel and cobalt precursors to yield [Ni{S2CN(CH2CH2PPh2)2}2] and [Co{S2CN(CH2CH2PPh2)2}3]. Addition of [AuCl(tht)] (tht = tetrahydrothiophene) to [Ni{S2CN(CH2CH2PPh2)2}2] leads to formation of the pentametallic complex, [Ni{S2CN(CH2CH2PPh2AuCl)2}2]. In contrast, addition of [PdCl2(py)2] (py = pyridine) to [Ni{S2CN(CH2CH2PPh2)2}2] does not lead to a trimetallic complex but instead yields the transmetalated cyclic compound [Pd{S2CN(CH2CH2PPh2)2}]2, which was structurally characterized. The same product is obtained directly from [PdCl2(py)2] and KS2CN(CH2CH2PPh2)2. In contrast, the same reaction with [PtCl2(NCPh)2] yields the oligomer, [Pt{S2CN(CH2CH2PPh2)2}]n. Reaction of KS2CN(CH2CH2PPh2)2 with cis-[RuCl2(dppm)2] provides [Ru{S2CN(CH2CH2PPh2)2}(dppm)2]+, which reacts with [AuCl(tht)] to yield [Ru{S2CN(CH2CH2PPh2AuCl)2}(dppm)2]+. Addition of [M(CO)4(pip)2] (M = Mo, W) to the same precursor leads to formation of the bimetallic compounds [(dppm)2Ru{S2CN(CH2CH2PPh2)2}M(CO)4]+, while treatment with [ReCl(CO)5] yields [(dppm)2Ru{S2CN(CH2CH2PPh2)2}ReCl(CO)3]+. Reaction of KS2CN(CH2CH2PPh2)2 with [Os(CH═CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) provides [Os(CH═CHC6H4Me-4){S2CN(CH2CH2PPh2)2}(CO)(PPh3)2], but reaction with the analogous ruthenium precursor fails to yield a clean product.

The aza-crown ether compounds 1-aza-15-crown-5 and 1,10-diaza-18-crown-6 react with sodium hydroxide and carbon disulfide to provide the dithiocarbamates [15]aneO4-NCS2Na and NaS2CN-[18]aneO4-NCS2Na in good yield. The complexes [MRCl(CO)(L)(PPh3)2] (M = Ru, R = H, CH═CHC6H4Me-4, CH═CHBut, CH═CH-pyrenyl-1, C(C≡CPh)═CHPh; M = Os, R = H, CH═CH-pyrenyl-1; L = 2,1,3-benzothiadiazole or no ligand) undergo reaction with [15]aneO4-NCS2Na and NaS2CN-[18]aneO4-NCS2Na to yield [MR(S2CN-[15]aneO4)(CO)(PPh3)2] and [{MR(CO)(PPh3)2}2(S2CN-[18]aneO4-NCS2)], respectively. In a similar manner, cis-[RuCl2(dppm)2] provides [Ru(S2CN-[15]aneO4)(dppm)2]+ and [{Ru(dppm)2}2(S2CN-[18]aneO4-NCS2)]2+, respectively. Reaction of [Ru(CH═CHC6H4Me-4)(S2CN-[15]aneO4)(CO)(PPh3)2] with excess HC≡CBut leads to the formation of the alkynyl complex [Ru(C≡CBut)(S2CN-[15]aneO4)(CO)(PPh3)2]. Treatment of [OsHCl(CO)(BTD)(PPh3)2] with [HC≡C-bpyReCl(CO)3] results in the bimetallic compound [Os{CH═CH-bpyReCl(CO)3}Cl(CO)(BTD)(PPh3)2]. This reacts with [15]aneO4-NCS2Na and NaS2CN-[18]aneO4-NCS2Na to yield [Os{CH═CH-bpyReCl(CO)3}(S2CN-[15]aneO4)(CO)(PPh3)2] and [{Os{CH═CH-bpyReCl(CO)3}(CO)(PPh3)2}2(S2CN-[18]aneO4-NCS2)], respectively. NMR studies provide information on the selectivity of binding of Li and Na ions. The structures of [RuR(S2CN-[15]aneO4)(CO)(PPh3)2] (R = H, CH═CHC6H4Me-4, CH═CH-pyrenyl-1) are also reported.

The chromo-fluorogenic detection of carbon monoxide in air has been achieved using a simple, inexpensive system based on ruthenium(II). This probe shows exceptional sensitivity and selectivity in its sensing behavior in the solid state. A color response visible to the naked eye is observed at 5 ppb of CO, and a remarkably clear color change occurs from orange to yellow at the onset of toxic CO concentrations (100 ppm) in air. Even greater sensitivity (1 ppb) can be achieved through a substantial increase in turn-on emission fluorescence in the presence of carbon monoxide, both in air and in solution. No response is observed with other gases including water vapor. Immobilization of the probe on a cellulose strip allows the system to be applied in its current form in a simple optoelectronic device to give a numerical reading and/or alarm.

The room-temperature ionic liquid, [C4C1im][HSO4], provides a multi-faceted medium in which to convert fructose to the versatile chemical building block, 5-hydroxymethylfurfural (HMF). A range of metal salts have been investigated in order to establish some of the properties required for the optimization of this process. This has led to almost quantitative conversion of fructose to 5-HMF in a system that is both selective for the desired product, less energy intensive, and more environmentally benign than the commercial process.Keywords: Biorefinery; Biorenewables; Catalysis; Cellulose; Lignocelluloses; Platform chemicals

The gold(I) complexes [Au{S2CN(CH2CH═CH2)2}(L)] [L = PPh3, PCy3, PMe3, CNtBu, IDip] are prepared from KS2CN(CH2CH═CH2)2 and [(L)AuCl]. The compounds [L2(AuCl)2] (L2 = dppa, dppf) yield [(L2){AuS2CN(CH2CH═CH2)2}2], while the cyclic complex [(dppm){Au2S2CN(CH2CH═CH2)2}]OTf is obtained from [dppm(AuCl)2] and AgOTf followed by KS2CN(CH2CH═CH2)2. The compound [Au2{S2CN(CH2CH═CH2)2}2] is prepared from [(tht)AuCl] (tht = tetrahydrothiophene) and the diallyldithiocarbamate ligand. This product ring-closes with [Ru(═CHPh)Cl2(SIMes)(PCy3)] to yield [Au2(S2CNC4H6)2], whereas ring-closing of [Au{S2CN(CH2CH═CH2)2}(PR3)] fails. Warming [Au2{S2CN(CH2CH═CH2)2}2] results in formation of gold nanoparticles with diallydithiocarbamate surface units, while heating [Au2(S2CNC4H6)2] with NaBH4 results in nanoparticles with 3-pyrroline dithiocarbamate surface units. Larger nanoparticles with the same surface units are prepared by citrate reduction of HAuCl4 followed by addition of the dithiocarbamate. The diallydithiocarbamate-functionalized nanoparticles undergo ring-closing metathesis using [Ru(═CHC6H4OiPr-2)Cl2(SIMes)]. The interaction between the dithiocarbamate units and the gold surface is explored using computational methods to reveal no need for a countercation. Preliminary calculations indicate that the Au–S interactions are substantially different from those established in theoretical and experimental studies on thiolate-coated nanoparticles. Structural studies are reported for [Au{S2CN(CH2CH═CH2)2}(PPh3)] and [Au2{S2CN(CH2CH═CH2)2}2]. In the latter, exceptionally short intermolecular aurophilic interactions are observed.

The new DO3A-derived dithiocarbamate ligand, DO3A-tBu-CS2K, is formed by treatment of the ammonium salt [DO3A-tBu]HBr with K2CO3 and carbon disulfide. DO3A-tBu-CS2K reacts with the ruthenium complexes cis-[RuCl2(dppm)2] and [Ru(CH═CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) to yield [Ru(S2C-DO3A-tBu)(dppm)2]+ and [Ru(CH═CHC6H4Me-4)(S2C-DO3A-tBu)(CO)(PPh3)2], respectively. Similarly, the group 10 metal complexes [Pd(C,N-C6H4CH2NMe2)Cl]2 and [PtCl2(PPh3)2] form the dithiocarbamate compounds, [Pd(C,N-C6H4CH2NMe2)(S2C-DO3A-tBu)] and [Pt(S2C-DO3A-tBu)(PPh3)2]+, under the same conditions. The linear gold complexes [Au(S2C-DO3A-tBu)(PR3)] are formed by reaction of [AuCl(PR3)] (R = Ph, Cy) with DO3A-tBu-CS2K. However, on reaction with [AuCl(tht)] (tht = tetrahydrothiophene), the homoleptic digold complex [Au(S2C-DO3A-tBu)]2 is formed. Further homoleptic examples, [M(S2C-DO3A-tBu)2] (M = Ni, Cu) and [Co(S2C-DO3A-tBu)3], are formed from treatment of NiCl2·6H2O, Cu(OAc)2, or Co(OAc)2, respectively, with DO3A-tBu-CS2K. The molecular structure of [Ni(S2C-DO3A-tBu)2] was determined crystallographically. The tert-butyl ester protecting groups of [M(S2C-DO3A-tBu)2] (M = Ni, Cu) and [Co(S2C-DO3A-tBu)3] are cleaved by trifluoroacetic acid to afford the carboxylic acid products, [M(S2C-DO3A)2] (M = Ni, Cu) and [Co(S2C-DO3A)3]. Complexation with Gd(III) salts yields trimetallic [M(S2C-DO3A-Gd)2] (M = Ni, Cu) and tetrametallic [Co(S2C-DO3A-Gd)3], with r1 values of 11.5 (Co) and 11.0 (Cu) mM–1 s–1 per Gd center. DO3A-tBu-CS2K can also be used to prepare gold nanoparticles, Au@S2C-DO3A-tBu, by displacement of the surface units from citrate-stabilized nanoparticles. This material can be transformed into the carboxylic acid derivative Au@S2C-DO3A by treatment with trifluoroacetic acid. Complexation with Gd(OTf)3 or GdCl3 affords Au@S2C-DO3A-Gd with an r1 value of 4.7 mM–1 s–1 per chelate and 1500 mM–1 s–1 per object.

The new, unsymmetrical dithiocarbamate ligands, KS2CN(CH2CH═CH2)Me and KS2CN(CH2C≡CH)Me, are formed from the respective amines on reaction with KOH and carbon disulfide. The homoleptic complexes [Ni{S2CN(CH2CH═CH2)Me}2] and [M{S2CN(CH2C≡CH)Me}2] (M = Ni, Pd, Pt) are formed on reaction with suitable metal precursors. Conversion between the two pendant functionalities was confirmed by hydrogenation of [Ni{S2CN(CH2C≡CH)Me}2] to yield [Ni{S2CN(CH2CH═CH2)Me}2]. The monodithiocarbamate compounds of group 8, 10, and 11 metals, [Ru{S2CN(CH2CH═CH2)Me}(dppm)2]+, [Ru(CH═CHC6H4Me-4){S2CN(CH2CH═CH2)Me}(CO)(PPh3)2], [Ni{S2CN(CH2CH═CH2)Me}(dppp)]+, and [Au{S2CN(CH2CH═CH2)Me}(PPh3)] were formed successfully. Using KS2CN(CH2C≡CH)Me, the complex [Ru{S2CN(CH2C≡CH)Me}(dppm)2]+ was obtained from cis-[RuCl2(dppm)2]. One palladium example, [Pd{S2CN(CH2C≡CH)Me}(PPh3)2]+, was also isolated in low yield. However, under the typical conditions employed, a rearrangement reaction prevented isolation of further group 10 propargyl-dithiocarbamate products. Over the extended reaction time required, Me(HC≡CCH2)NCS2– was found to undergo a remarkable, atom-efficient cyclization to form the thiazolidine-2-thione, H2C═CCH2N(Me)C(═S)S, in high yield, with MeC═CHN(Me)C(═S)S as the minor product. The reactivity of the pendant triple bonds in [Ni{S2CN(CH2C≡CH)Me}2] was probed in the reaction with [RuH(CO)(S2P(OEt)2)(PPh3)2] to form the trimetallic example [Ni{S2CN(Me)CH2CH═CHRu(CO)(S2P(OEt)2)(PPh3)2}2], while the copper(I) catalyzed reaction with benzylazide yielded the triazole product, [Ni{S2CN(Me)CH2(C2HN3)Bz}2]. KS2CN(CH2C≡CH)Me was also used to prepare the gold nanoparticles, Au@S2CN(CH2C≡CH)Me. Structural studies are reported for [Ru(CH═CHC6H4Me-4){S2CN(CH2CH═CH2)Me}(CO)(PPh3)2] and [Ru{S2CN(CH2C≡CH)Me}(dppm)2]PF6.

Immobilised [Cu(NHC)] catalysts are reported for the preparation of 1,2,3-triazoles. In addition to showing outstanding catalytic activity, the catalyst systems are easy to prepare and can be recycled many times.

The versatile precursors [Ru(CH═CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) and [Ru(C(C≡CPh)═CHPh)Cl(CO)(PPh3)2] were treated with isonicotinic acid, 4-cyanobenzoic acid, and 4-(4-pyridyl)benzoic acid under basic conditions to yield [Ru(vinyl)(O2CC5H4N)(CO)(PPh3)2], [Ru(vinyl)(O2CC6H4CN-4)(CO)(PPh3)2], and [Ru(vinyl){O2CC6H4(C5H4N)-4}(CO)(PPh3)2], respectively. The osmium analogue [Os(CH═CHC6H4Me-4)(O2CC5H4N)(CO)(PPh3)2] was also prepared. cis-[RuCl2(dppm)2] was used to prepare the cationic compounds [Ru(O2CC5H4N)(dppm)2]+ and [Ru{O2CC6H4(C5H4N)-4}(dppm)2]+. The treatment of 2 equiv of [Ru(C(C≡CPh)═CHPh)(O2CC5H4N)(CO)(PPh3)2] and [Ru(O2CC5H4N)(dppm)2]+ with AgOTf led to the trimetallic compounds [{Ru(C(C≡CPh)═CHPh)(CO)(PPh3)2(O2CC5H4N)}2Ag]+ and [{Ru(dppm)2(O2CC5H4N)}2Ag]3+. In a similar manner, the reaction of [Ru(O2CC5H4N)(dppm)2]+ with PdCl2 or K2PtCl4 yielded [{Ru(dppm)2(O2CC5H4N)}2MCl2]2+ (M = Pd, Pt). The reaction of [RuHCl(CO)(BTD)(PPh3)2] with HC≡CC6H4F-4 provided [Ru(CH═CHC6H4F-4)Cl(CO)(BTD)(PPh3)2], which was treated with isonicotinic acid and base to yield [Ru(CH═CHC6H4F-4)(O2CC5H4N)(CO)(PPh3)2]. The addition of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) resulted in the formation of [Ru(CH═CHC6H4F-4){O2CC5H4N(AuC6F5)}(CO)(PPh3)2]. Similarly, [Ru(vinyl)(O2CC6H4CN-4)(CO)(PPh3)2] reacted with [Au(C6F5)(tht)] to provide [Ru(vinyl){O2CC6H4(CNAuC6F5)-4}(CO)(PPh3)2]. The reaction of 4-cyanobenzoic acid with [Au(C6F5)(tht)] yielded [Au(C6F5)(NCC6H4CO2H-4)]. This compound was used to prepare [Ru(CH═CHC6H4F-4){O2CC6H4(CNAuC6F5)-4}(CO)(PPh3)2], which was also formed on treatment of [Ru(CH═CHC6H4F-4)(O2CC6H4CN-4)(CO)(PPh3)2] with [Au(C6F5)(tht)]. The known compound [RhCl2(NC5H4CO2)(NC5H4CO2Na)3] and the new complex [RhCl2{NC5H4(C6H4CO2)-4}{NC5H4(C6H4CO2Na)-4}3] were prepared from RhCl3·3H2O and isonicotinic acid or 4-(4-pyridyl)benzoic acid, respectively. The former was treated with [Ru(CH═CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] to yield [RhCl2{NC5H4CO2(Ru(CH═CHC6H4Me-4)(CO)(PPh3)2}4]Cl. As an alternative route to pentametallic compounds, the Pd-coordinated porphyrin [(Pd-TPP)(p-CO2H)4] was treated with 4 equiv of [Ru(CH═CHR)Cl(CO)(BTD)(PPh3)2] in the presence of a base to yield [(Pd-TPP){p-CO2Ru(CH═CHR)(CO)(PPh3)2}4] (R = C6H4Me-4, CPh2OH). Where R = CPh2OH, treatment with HBF4 led to the formation of [(Pd-TPP){p-CO2Ru(═CHCH═CPh2)(CO)(PPh3)2}4](BF4)4. [(Pd-TPP){p-CO2Ru(dppm)2}4](PF6)4 was prepared from [(Pd-TPP)(p-CO2H)4] and cis-[RuCl2(dppm)2]. The reaction of AgNO3 with sodium borohydride in the presence of [Ru(O2CC5H4N)(dppm)2]+ or [RuR{O2CC6H4(C5H4N)-4}(dppm)2]+ provided silver nanoparticles Ag@[NC5H4CO2Ru(dppm)2]+ and Ag@[NC5H4{C6H4CO2Ru(dppm)2}-4]+.

The palladium(II) dimer, [Pd(C,N-C6H4CH2NMe2)Cl]2 reacts with two equivalents of the NHC·CS2 zwitterionic ligands [NHC = IPr (1,3-diisopropylimidazol-2-ylidene), ICy (1,3-dicyclohexylimidazol-2-ylidene), IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IDip (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), SIMes (1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene)] in the presence of NH4PF6, to yield the cationic products [Pd(C,N-C6H4CH2NMe2)(S2C·NHC)]+. In a similar fashion, the compounds [Pd(C,N-bzq)(S2C·NHC)]+ (bzq = benzo[h]quinolinyl, NHC = ICy, IMes, IDip) are obtained from the corresponding dimer [Pd(C,N-bzq)Cl]2. The bis(phosphine) compounds [Pd(S2C·NHC)(PPh3)2]2+ (NHC = ICy, IMes, IDip, SIMes) are obtained on treatment of [PdCl2(PPh3)2] with NHC·CS2 zwitterions in the presence of NH4PF6. The reaction of [PdCl2(dppf)] with IMes·CS2 and NH4PF6 provides the complex [Pd(S2C·IMes)(dppf)]2+. The complexes [Pd(S2C·NHC)(PPh3)2](PF6)2 (NHC = IMes, IDip) were active pre-catalysts (1 mol% loading) for the conversion of benzo[h]quinoline to 10-methoxybenzo[h]quinoline in the presence of PhI(OAc)2 and methanol. The intermediacy of [Pd(C,N-bzq)(S2C·NHC)]+ was supported by the high yield of 10-methoxybenzo[h]quinoline using [Pd(C,N-bzq)(S2C·IDip)]+ to promote the same reaction. Small amounts of 2,10-dimethoxybenzo[h]quinoline were also isolated from these reactions. Using [Pd(C,N-bzq)(S2C·IDip)]+ and N-chlorosuccinimide as the oxidant led to the formation of 10-chlorobenzo[h]quinoline in moderate yield from benzo[h]quinoline. The molecular structures of [Pd(S2C·IMes)(PPh3)2](PF6)2 and [Pd(S2C·IMes)(dppf)](PF6)2 were determined crystallographically.

The ruthenium(II) complexes [Ru(CHCHR){κ2-S2P(OEt)2}(CO)(PPh3)2] (R = But, C6H4Me-4) are formed on reaction of (NH4)[S2P(OEt)2] with [Ru(CHCHR)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole), while the enynyl complex [Ru(C(CCPh)CHPh)Cl(CO)(PPh3)2] loses a phosphine on treatment with the same ligand to yield [Ru(η3-PhCC–CCHPh){κ2-S2P(OEt)2}(CO)(PPh3)]. The stilbenyl complexes [Ru(CPhCHPh)Cl(CA)(PPh3)2] (A = O, S) react with (NH4)[S2P(OEt)2] to provide the dimers [Ru(CPhCHPh){μ–κ1–κ2–S2P(OEt)2}(CA)(PPh3)]2. Treatment of the thiocarbonyl complex with carbon monoxide results in migratory insertion of the vinyl and CS ligands to provide [Ru(η2-SCCPhCHPh){κ2-S2P(OEt)2}(CO)(PPh3)]. On treatment with excess 4-ethynyltoluene, the known compound [RuH{κ2-S2P(OEt)2}(CO)(PPh3)2] undergoes insertion of the alkyne to provide an alternative route to [Ru(CHCHC6H4Me-4){κ2-S2P(OEt)2}(CO)(PPh3)2]. The compounds [Ru(CHCHR){κ2-S2P(OEt)2}(CO)(PPh3)2] (R = n-C4H9, CH2OSi(But)Me2, CO2Me, Fc, CPh2OH, (HO)C6H10) were prepared cleanly by this route using HCCR. On stirring [RuH{κ2-S2P(OEt)2}(CO)(PPh3)2] over a longer period of time with excess 4-ethynyltoluene, the acetylide [Ru(CCC6H4Me–4){κ2-S2P(OEt)2}(CO)(PPh3)2] is generated. Heating [Ru(CHCHC6H4Me-4){κ2-S2P(OEt)2}(CO)(PPh3)2] with excess 3,3-dimethylbut-1-yne in 1,2-dichloroethane led to elimination of the vinyl ligand and formation of the acetylide compound [Ru(CCBut){κ2-S2P(OEt)2}(CO)(PPh3)2]. A small amount of the side product, [RuCl{κ2-S2P(OEt)2}(CO)(PPh3)2], was also formed. This could be obtained directly from the reaction of [RuH{κ2-S2P(OEt)2}(CO)(PPh3)2] with N-chlorosuccinimide. The related mixed-donor ligand, K[OP(S)(OEt)2], reacts with [Ru(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] to yield [Ru(CHCHC6H4Me-4){κ2-OP(S)(OEt)2}(CO)(PPh3)2]. The molecular structure of [Ru(CHCHCPh2OH){κ2-S2P(OEt)2}(CO)(PPh3)2] was determined crystallographically.

The ruthenium(II) complexes [Ru(R)(κ2-S2C·IPr)(CO)(PPh3)2]+ (R = CHCHBut, CHCHC6H4Me-4, C(CCPh)CHPh) are formed on reaction of IPr·CS2 with [Ru(R)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(CCPh)CHPh)Cl(CO)(PPh3)2] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CHCHC6H4Me-4)(κ2-S2C·ICy)(CO)(PPh3)2]+ and [Ru(C(CCPh)CHPh)(κ2-S2C·ICy)(CO)(PPh3)2]+ are formed in the same manner when ICy·CS2 is employed. The ligand IMes·CS2 reacts with [Ru(R)Cl(CO)(BTD)(PPh3)2] to form the compounds [Ru(R)(κ2-S2C·IMes)(CO)(PPh3)2]+ (R = CHCHBut, CHCHC6H4Me-4, C(CCPh)CHPh). Two osmium analogues, [Os(CHCHC6H4Me-4)(κ2-S2C·IMes)(CO)(PPh3)2]+ and [Os(C(CCPh)CHPh)(κ2-S2C·IMes)(CO)(PPh3)2]+ were also prepared. When the more bulky diisopropylphenyl derivative IDip·CS2 is used, an unusual product, [Ru(κ2-SC(H)S(CHCHC6H4Me-4)·IDip)Cl(CO)(PPh3)2]+, with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] also reacts with IMes·CS2 and NH4PF6 to yield the analogous product [Ru{κ2-SC(H)S(CHCHC6H4Me-4)·IMes}Cl(CO)(PPh3)2]+via the intermediate [Ru(CHCHC6H4Me-4)(κ2-S2C·IMes)(CO)(PPh3)2]+. Structural studies are reported for [Ru(CHCHC6H4Me-4)(κ2-S2C·IPr)(CO)(PPh3)2]PF6 and [Ru(C(CCPh)CHPh)(κ2-S2C·ICy)(CO)(PPh3)2]PF6.

The new 2-phenylthiocarbamoyl-1,3-dimesitylimidazolium inner salt (IMes·CSNPh) reacts with [AuCl(L)] in the presence of NH4PF6 to yield [(L)Au(SCNPh·IMes)]+ (L = PMe3, PPh3, PCy3, CNBut). The carbene-containing precursor [(IDip)AuCl] reacts with IMes·CSNPh under the same conditions to afford the complex [(IDip)Au(SCNPh·IMes)]+ (IDip = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). Treatment of the diphosphine complex [(dppm)(AuCl)2] with one equivalent of IMes·CSNPh yields the digold metallacycle, [(dppm)Au2(SCNPh·IMes)]2+, while reaction of [L2(AuCl)2] with two equivalents of IMes·CSNPh results in [(L2){Au(SCNPh·IMes)}2]2+ (L2 = dppb, dppf, or dppa; dppb = 1,4-bis(diphenylphosphino)butane, dppf = 1,1′-bis(diphenylphosphino)ferrocene, dppa = 1,4-bis(diphenylphosphino)acetylene). The homoleptic complex [Au(SCNPh·IMes)2]+ is formed on reaction of [AuCl(tht)] (tht = tetrahydrothiophene) with two equivalents of the imidazolium-2-phenylthiocarbamoyl ligand. This product reacts with AgOTf to yield the mixed metal compound [AuAg(SCNPh·IMes)2]2+. Over time, the unusual trimetallic complex [Au(AgOTf)2(SCNPh·IMes)2]+ is formed. The sulfur-oxygen mixed-donor ligands IMes·COS and SIMes·COS (SIMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) were used to prepare [(L)Au(SOC·IMes)]+ and [(L)Au(SOC·SIMes)]+ from [(L)AuCl] (L = PPh3, CNtBu). The bimetallic examples [(dppf){Au(SOC·IMes)}2]2+ and [(dppf){Au(SOC·SIMes)}2]2+ were synthesized from the reaction of [(dppf)(AuCl)2] with the appropriate ligand. Reaction of [(tht)AuCl] with one equivalent of IMes·COS or SIMes·COS yields [Au(SOC·IMes)2]+ and [Au(SOC·SIMes)2]+, respectively. The compounds [(Ph3P)Au(SCNPh·IMes)]PF6, [(Cy3P)Au(SCNPh·IMes)]PF6 and [Au(AgOTf)2(SCNPh·IMes)2]OTf were characterized crystallographically.

The ligands KS2CN(Bz)CH2CH2N(Bz)CS2K (K2L1), N(CH2CH2N(Me)CS2Na)3 (Na3L2), and the new chelates {(CH2CH2)NCS2Na}3 (Na3L3) and {CH2CH2N(CS2Na)CH2CH2CH2NCS2Na}2 (Na4L4), react with the gold(I) complexes [ClAu(PR3)] (R = Me, Ph, Cy) and [ClAu(IDip)] to yield di-, tri-and tetragold compounds. Larger metal units can also be coordinated by the longer, flexible linker, K2L1. Thus two equivalents of cis-[PtCl2(PEt3)2] react with K2L1 in the presence of NH4PF6 to yield the bimetallic complex [L1{Pt(PEt3)2}2](PF6)2. The compounds [NiCl2(dppp)] and [MCl2(dppf)] (M = Ni, Pd, Pt; dppp = 1,3-bis(diphenylphosphino)propane, dppf = 1,1'-bis(diphenylphosphino)ferrocene) also yield the dications, [L1{Ni(dppp)}2]2+ and [L1{Ni(dppf)}2]2+ in an analogous fashion. In the same manner, reaction between [(L′2)(AuCl)2] (L′2 = dppm, dppf; dppm = bis(diphenylphosphino)methane) and KS2CN(Bz)CH2CH2N(Bz)CS2K yield [L1{Au2(L′2)}2]. The molecular structures of [L1{M(dppf)}2](PF6)2 (M = Ni, Pd) and [L1{Au(PR3)}2] (R = Me, Ph) are reported.

The imidazolium-2-dithiocarboxylate ligands IPr·CS2, IMes·CS2, and IDip·CS2 react with [AuCl(PPh3)] to yield [(Ph3P)Au(S2C·IPr)]+, [(Ph3P)Au(S2C·IMes)]+, and [(Ph3P)Au(S2C·IDip)]+, respectively. The compounds [(L)Au(S2C·IMes)]+ are prepared from the reaction of IMes·CS2 with [AuCl(L)] (L = PMe3, PCy3, CNtBu). The carbene-containing precursor [(IDip)AuCl] reacts with IPr·CS2 and IMes·CS2 to afford the complexes [(IDip)Au(S2C·IPr)]+ and [(IDip)Au(S2C·IMes)]+ with two carbene units, one bound to the metal center and the other to the dithiocarboxylate unit. Treatment of the diphosphine-gold complex [(dppm)(AuCl)2] with 1 equiv of IMes·CS2 yields [(dppm)Au2(S2C·IMes)]2+, while the reaction of [L2(AuCl)2] (L2 = dppb, dppf) with 2 equiv of IMes·CS2 results in [(L2){Au(S2C·IMes)}2]2+. The homoleptic complexes [Au(S2C·IPr)2]2+, [Au(S2C·IMes)2]2+, and [Au(S2C·IDip)2]2+ are obtained from the reaction of [AuCl(tht)] with 2 equiv of the appropriate imidazolium-2-dithiocarboxylate ligand. The compounds [(Ph3P)Au(S2C·NHC)]+ (NHC = IMes, IDip) and [(IDip)Au(S2C·NHC)]+ (NHC = IPr, IMes) are characterized crystallographically. The IMes·CS2 ligand is also used to prepare functionalized gold nanoparticles with diameters of 11.5 (±1.2) and 2.6 (±0.3) nm.

The complex cis-[RuCl2(dppm)2] reacts with the amine-terminated dithiocarbamates KS2CN(CH2CH2NEt2)2 and KS2CN(CH2CH2CH2NMe2)2 to form the compounds [Ru{S2CN(CH2CH2NEt2)2}(dppm)2]+ and [Ru{S2CN(CH2CH2CH2NMe2)2}(dppm)2]+, respectively. The methoxy-terminated dithiocarbamate compound [Ru{S2CN(CH2CH2OMe)2}(dppm)2]+ was also prepared from the same precursor using KS2CN(CH2CH2OMe)2. The alkenyl complexes [RuRCl(CO)(BTD)(PPh3)2] (R = CHCHBut, CHCHC6H4Me-4, CHCHCPh2OH), [Ru(C(CCBut)CHBut)Cl(CO)(PPh3)2] and [Os(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] also react cleanly with KS2CN(CH2CH2CH2NMe2)2 and KS2CN(CH2CH2NEt2)2 to yield [MR{S2CN(CH2CH2CH2NMe2)2}(CO)(PPh3)2] and [MR{S2CN(CH2CH2NEt2)2}(CO)(PPh3)2], respectively. In a similar fashion, the compounds [RuR{S2CN(CH2CH2OMe2)2}(CO)(PPh3)2] (R = CHCHBut, CHCHC6H4Me-4, C(CCBut)CHBut) were also prepared. Treatment of [Ru(CHCHBut){S2CN(CH2CH2CH2NMe2)2}(CO)(PPh3)2] and [Ru{S2CN(CH2CH2NEt2)2}(dppm)2]+ with trifluoroacetic acid affords the ammonium complexes [Ru(CHCHBut){S2CN(CH2CH2CH2NHMe2)2}(CO)(PPh3)2]2+ and [Ru{S2CN(CH2CH2NHEt2)2}(dppm)2]2+, while the same reagent generates the tricationic vinylcarbene complex [Ru(CHCHCPh2){S2CN(CH2CH2CH2NHMe2)2}(CO)(PPh3)2]3+ through loss of water from [Ru(CHCHCPh2OH){S2CN(CH2CH2CH2NMe2)2}(CO)(PPh3)2]. The structures of [Ru{S2CN(CH2CH2OMe)2}(dppm)2]PF6 and [Ru(CHCHC6H4Me-4){S2CN(CH2CH2OMe)2}(CO)(PPh3)2] were determined crystallographically.

The complex cis-[RuCl2(dppm)2] reacts with the diallyldithiocarbamate KS2CN(CH2CH═CH2)2 to form [Ru{S2CN(CH2CH═CH2)2}(dppm)2]+. The same ligand was also used to prepare the alkenyl complexes [RuR{S2CN(CH2CH═CH2)2}(CO)(PPh3)2] (R = CH═CHBut, CH═CHC6H4Me-4, C(C≡CBut)═CHBut) from the corresponding precursors [RuRCl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) and [Ru(C(C≡CBut)═CHBut)Cl(CO)(PPh3)2]. The complexes [Ni{S2CN(CH2CH═CH2)2}(dppp)]+ (dppp =1,3-bis(diphenylphosphino)propane) and [M{S2CN(CH2CH═CH2)2}(dppf)]+ (M = Ni, Pd, Pt; dppf = 1,1′-bis(diphenylphosphino)ferrocene) were prepared from the respective precursors [MCl2(L2)] (L2 = dppp, dppf) and KS2CN(CH2CH═CH2)2 in the presence of NH4PF6. In a similar manner, treatment of the cyclometalated dimer [Pd(C,N-CH2C6H4NMe2)Cl]2 with the dithiocarbamate ligand yielded [Pd(C,N-CH2C6H4NMe2){S2CN(CH2CH═CH2)2}]. The homoleptic literature complexes [Ni{S2CN(CH2CH═CH2)2}2] and [Co{S2CN(CH2CH═CH2)2}3] were also prepared and characterized. Ring-closing metathesis catalyzed by [Ru(═CHPh)Cl2(SIMes)(PCy3)] converted [Ni{S2CN(CH2CH═CH2)2}2], [Pd(C,N-CH2C6H4NMe2){S2CN(CH2CH═CH2)2}], [Ni{S2CN(CH2CH═CH2)2}(dppp)]+, [Pt{S2CN(CH2CH═CH2)2}(dppf)]+, [Ru{S2CN(CH2CH═CH2)2}(dppm)2]+, and [Ru(CH═CHC6H4Me-4){S2CN(CH2CH═CH2)2}(CO)(PPh3)2] into the corresponding 3-pyrroline dithiocarbamate compounds [Ni(S2CNC4H6)2], [Pd(C,N-CH2C6H4NMe2)(S2CNC4H6)], [Ni(S2CNC4H6)(dppp)]+, [Pt(S2CNC4H6)(dppf)]+, [Ru(S2CNC4H6)(dppm)2]+, and [Ru(CH═CHC6H4Me-4)(S2CNC4H6)(CO)(PPh3)2], respectively. These complexes were also directly prepared from the reaction of the appropriate starting materials with preformed KS2CNC4H6. The more sterically crowded complex [Co{S2CN(CH2CH═CH2)2}3] failed to give a reaction with the metathesis catalyst, although it could be prepared directly from KS2CNC4H6 and cobalt acetate. The compounds [Ru(CH═CHC6H4Me-4){S2CN(CH2CH═CH2)2}(CO)(PPh3)2], [Ni{S2CN(CH2CH═CH2)2}(dppp)]PF6, and [Ni(S2CNC4H6)(dppp)]PF6 were characterized crystallographically.

Reaction of [AuCl(PPh3)] with the zwitterion S2CNC4H8NH2 yields [(Ph3P)Au(S2CNC4H8NH2)]BF4. Treatment of this species with NEt3 and CS2 followed by [AuCl(PPh3)] leads to [{(Ph3P)Au}2(S2CNC4H8NCS2)], which can also be obtained directly from [AuCl(PPh3)] and KS2CNC4H8NCS2K. A heterobimetallic variant, [(dppm)2Ru(S2CNC4H8NCS2)Au(PPh3)]+, can be prepared by the sequential reaction of [(dppm)2Ru(S2CNC4H8NH2)]2+ with NEt3 and CS2 followed by [AuCl(PPh3)]. Reaction of the same ruthenium precursor with [(dppm)(AuCl)2] under similar conditions yields the trimetallic complex [(dppm)2Ru(S2CNC4H8NCS2)Au2(dppm)]2+. Attempts to prepare the compound [(dppm)Au2(S2CNC4H8NH2)]2+ from [(dppm)(AuCl)2] led to isolation of the known complex [{(dppm)Au2}2(S2CNC4H8NCS2)]2+ via a symmetrization pathway. [{(dppf)Au2}2(S2CNC4H8NCS2)]2+ was successfully prepared from [(dppf)(AuCl)2] and crystallographically characterized. In addition, a gold(III) trimetallic compound, [{(dppm)2Ru(S2CNC4H8NCS2)}2Au]3+, and a tetrametallic gold(I) species, [{(dppm)2Ru(S2CNC4H8NCS2)Au}2]2+, were also synthesized. This methodology was further exploited to attach the zwitterionic (dppm)2Ru(S2CNC4H8NCS2) unit to the surface of gold nanoparticles, which were generated in situ and found to be 3.4 (±0.3) and 14.4 (±2.5) nm in diameter depending on the method employed. Nanoparticles with a mixed surface topography were also explored.

Homobimetallic complexes of nickel, palladium and platinum, [(L2M)2(S2CNC4H8NCS2)]2+, are formed on reaction of the piperazine bis(dithiocarbamate) linker, KS2CNC4H8NCS2K, with [MCl2L2] (M = Ni, L2 = dppe, dppf; M = Pd, L2 = dppf; M = Pt, L = PEt3, PMePh2, PPh3, L2 = dppf). [{Pd(C,N-C6H4CH2NMe2)}2(S2CNC4H8NCS2)] can be obtained in the same way. On reaction of [MCl2L2] (M = Pd, Pt) with the zwitterion S2CNC4H8NH2, a symmetrisation process occurs to yield a mixture of the complexes [M(S2CNC4H8NH2)L2]2+ and [(L2M)2(S2CNC4H8NCS2)]2+. However, the monometallic complexes [L2Ni(S2CNC4H8NH2)]2+ (L2 = dppe, dppf) and [(L2Ni)2(S2CNC4H8NCS2)]2+ can be prepared without ready symmetrisation. Starting from the previously reported [(dppm)Ru(S2CNC4H8NH2)]2+, the heterotrimetallic products [(dppm)Ru(S2CNC4H8NCS2)M(dppf)]2+ (M = Pd, Pt) can be prepared without symmetrisation occurring. The crystal structures of five complexes are reported. The metalla-dithiocarbamate complexes [L2Ni(S2CNC4H8NCS2)] (L2 = dppe, dppf) were used to functionalise the surface of gold nanoparticles by the displacement of a citrate shell to yield NiAu and FeNiAu materials.

The homobimetallic ruthenium(II) and osmium(II) complexes [{RuR(CO)(PPh3)2}2(S2COCH2C6H4CH2OCS2)] (R = CHCHBut, CHCHC6H4Me-4, C(CCPh)CHPh, CHCHCPh2OH) and [{Os(CHCHC6H4Me-4)(CO)(PPh3)2}2(S2COCH2C6H4CH2OCS2)] form readily from the reactions of [MRCl(CO)(BTD)(PPh3)2] (M = Ru or Os; BTD = 2,1,3-benzothiadiazole) with the dixanthate KS2COCH2C6H4CH2OCS2K. Addition of KS2COCH2C6H4CH2OCS2K to two equivalents of cis-[RuCl2(dppm)2] leads to the formation of [{(dppm)2Ru}2(S2COCH2C6H4CH2OCS2)]2+. The benzoate complexes [RuR{O2CC6H4(CH2OH)-4}(CO)(PPh3)2] (R = CHCHBut, CHCHC6H4Me-4, C(CCPh)CHPh) are obtained by treatment of [RuRCl(CO)(BTD)(PPh3)2] with 4-(hydroxymethyl)benzoic acid in the presence of base. Reaction of [RuHCl(CO)(PPh3)3] or [RuRCl(CO)(BTD)(PPh3)2] with 4-(hydroxymethyl)benzoic acid in the absence of base leads to formation of the chloride analogue [RuCl{O2CC6H4(CH2OH)-4}(CO)(PPh3)2]. The unsymmetrical complex [{Ru(CHCHC6H4Me-4)(CO)(PPh3)2}2(O2CC6H4CH2OCS2)] forms from the sequential treatment of [Ru(CHCHC6H4Me-4){O2CC6H4(CH2OH)-4}(CO)(PPh3)2] with base, CS2 and [Ru(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2]. The new mixed-donor xanthate-carboxylate ligand, KO2CC6H4CH2OCS2K is formed by treatment of 4-(hydroxymethyl)benzoic acid with excess KOH and two equivalents of carbon disulfide. This ligand reacts with two equivalents of [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] or cis-[RuCl2(dppm)2] to yield [{(dppm)2Ru}2(O2CC6H4CH2OCS2)]2+ or [{Ru(CHCHC6H4Me-4)(CO)(PPh3)2}2(O2CC6H4CH2OCS2)], respectively. Electrochemical experiments are also reported in which communication between the metal centres is investigated.

•A novel [(NHC)PdII] unit has been immobilised on silica coated nanoparticles.•Good activity shown in Suzuki-Miyaura and chloroarene dehalogenation reactions.•Pd-mediated transfer hydrogenation of carbonyl compounds is demonstratedA novel NHC–palladium(II) (NHC = N-heterocyclic carbene) complex and its immobilised version have been prepared and fully characterised. Optimisation studies led to good catalytic activities in Suzuki-Miyaura cross coupling and chloroarene dehalogenation reactions. Furthermore, the unexpected palladium-mediated transfer hydrogenation of a carbonyl compound is reported.Download full-size image

The sensing of carbon monoxide (CO) using electrochemical cells or semiconducting metal oxides has led to inexpensive alarms for the home and workplace. It is now recognised that chronic exposure to low levels of CO also poses a significant health risk. It is perhaps surprising therefore that the CO is used in cell-signalling pathways and plays a growing role in therapy. However, the selective monitoring of low levels of CO remains challenging, and it is this area that has benefited from the development of probes which give a colour or fluorescence response. This feature article covers the design of chromo-fluorogenic probes and their application to CO sensing in air, solution and in cells.

The versatile rhenium complex [ReCl(CO)3(bpyCCH)] (HCCbpy = 5-ethynyl-2,2′-bipyridine) is used to generate a series of bimetallic complexes through the hydrometallation of [MHCl(CO)(BTD)(PPh3)2] (M = Ru, Os; BTD = 2,1,3-benzothiadiazole). The ruthenium complex [Ru{CHCH-bpyReCl(CO)3}Cl(BTD)(CO)(PPh3)2] was characterised structurally. Ligand exchange reactions with bifunctional linkers bearing oxygen and sulfur donors provide access to tetra- and pentametallic complexes such as [{M{CHCH-bpyReCl(CO)3}(CO)(PPh3)2}2(S2CNC4H8NCS2)] and Fe[C5H4CO2M{CHCH-bpyReCl(CO)3}(CO)(PPh3)2]2. The effect of the group 8 metal on the photophysical properties of the rhenium centre was investigated using the complexes [Ru{CHCH-bpyReCl(CO)3}Cl(BTD)(CO)(PPh3)2] and [M{CHCH-bpyReCl(CO)3}{S2P(OEt)2}(CO)(PPh3)2] (M = Ru, Os). This revealed the quenching of the rhenium-based emission in favour of weak radiative processes based on the Ru and Os centres. The potential for exploiting this effect is illustrated by the reaction of [Ru{CHCH-bpyReCl(CO)3}Cl(CO)(BTD)(PPh3)2] with carbon monoxide, which results in a 5-fold fluorescence enhancement in the dicarbonyl product, [Ru{CHCH-bpyReCl(CO)3}Cl(CO)2(PPh3)2], as the quenching effect is disrupted.

The homobimetallic ruthenium(II) and osmium(II) complexes [{RuR(CO)(PPh3)2}2(S2COCH2C6H4CH2OCS2)] (R = CHCHBut, CHCHC6H4Me-4, C(CCPh)CHPh, CHCHCPh2OH) and [{Os(CHCHC6H4Me-4)(CO)(PPh3)2}2(S2COCH2C6H4CH2OCS2)] form readily from the reactions of [MRCl(CO)(BTD)(PPh3)2] (M = Ru or Os; BTD = 2,1,3-benzothiadiazole) with the dixanthate KS2COCH2C6H4CH2OCS2K. Addition of KS2COCH2C6H4CH2OCS2K to two equivalents of cis-[RuCl2(dppm)2] leads to the formation of [{(dppm)2Ru}2(S2COCH2C6H4CH2OCS2)]2+. The benzoate complexes [RuR{O2CC6H4(CH2OH)-4}(CO)(PPh3)2] (R = CHCHBut, CHCHC6H4Me-4, C(CCPh)CHPh) are obtained by treatment of [RuRCl(CO)(BTD)(PPh3)2] with 4-(hydroxymethyl)benzoic acid in the presence of base. Reaction of [RuHCl(CO)(PPh3)3] or [RuRCl(CO)(BTD)(PPh3)2] with 4-(hydroxymethyl)benzoic acid in the absence of base leads to formation of the chloride analogue [RuCl{O2CC6H4(CH2OH)-4}(CO)(PPh3)2]. The unsymmetrical complex [{Ru(CHCHC6H4Me-4)(CO)(PPh3)2}2(O2CC6H4CH2OCS2)] forms from the sequential treatment of [Ru(CHCHC6H4Me-4){O2CC6H4(CH2OH)-4}(CO)(PPh3)2] with base, CS2 and [Ru(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2]. The new mixed-donor xanthate-carboxylate ligand, KO2CC6H4CH2OCS2K is formed by treatment of 4-(hydroxymethyl)benzoic acid with excess KOH and two equivalents of carbon disulfide. This ligand reacts with two equivalents of [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] or cis-[RuCl2(dppm)2] to yield [{(dppm)2Ru}2(O2CC6H4CH2OCS2)]2+ or [{Ru(CHCHC6H4Me-4)(CO)(PPh3)2}2(O2CC6H4CH2OCS2)], respectively. Electrochemical experiments are also reported in which communication between the metal centres is investigated.

Homobimetallic complexes of nickel, palladium and platinum, [(L2M)2(S2CNC4H8NCS2)]2+, are formed on reaction of the piperazine bis(dithiocarbamate) linker, KS2CNC4H8NCS2K, with [MCl2L2] (M = Ni, L2 = dppe, dppf; M = Pd, L2 = dppf; M = Pt, L = PEt3, PMePh2, PPh3, L2 = dppf). [{Pd(C,N-C6H4CH2NMe2)}2(S2CNC4H8NCS2)] can be obtained in the same way. On reaction of [MCl2L2] (M = Pd, Pt) with the zwitterion S2CNC4H8NH2, a symmetrisation process occurs to yield a mixture of the complexes [M(S2CNC4H8NH2)L2]2+ and [(L2M)2(S2CNC4H8NCS2)]2+. However, the monometallic complexes [L2Ni(S2CNC4H8NH2)]2+ (L2 = dppe, dppf) and [(L2Ni)2(S2CNC4H8NCS2)]2+ can be prepared without ready symmetrisation. Starting from the previously reported [(dppm)Ru(S2CNC4H8NH2)]2+, the heterotrimetallic products [(dppm)Ru(S2CNC4H8NCS2)M(dppf)]2+ (M = Pd, Pt) can be prepared without symmetrisation occurring. The crystal structures of five complexes are reported. The metalla-dithiocarbamate complexes [L2Ni(S2CNC4H8NCS2)] (L2 = dppe, dppf) were used to functionalise the surface of gold nanoparticles by the displacement of a citrate shell to yield NiAu and FeNiAu materials.

The ligands KS2CN(Bz)CH2CH2N(Bz)CS2K (K2L1), N(CH2CH2N(Me)CS2Na)3 (Na3L2), and the new chelates {(CH2CH2)NCS2Na}3 (Na3L3) and {CH2CH2N(CS2Na)CH2CH2CH2NCS2Na}2 (Na4L4), react with the gold(I) complexes [ClAu(PR3)] (R = Me, Ph, Cy) and [ClAu(IDip)] to yield di-, tri-and tetragold compounds. Larger metal units can also be coordinated by the longer, flexible linker, K2L1. Thus two equivalents of cis-[PtCl2(PEt3)2] react with K2L1 in the presence of NH4PF6 to yield the bimetallic complex [L1{Pt(PEt3)2}2](PF6)2. The compounds [NiCl2(dppp)] and [MCl2(dppf)] (M = Ni, Pd, Pt; dppp = 1,3-bis(diphenylphosphino)propane, dppf = 1,1'-bis(diphenylphosphino)ferrocene) also yield the dications, [L1{Ni(dppp)}2]2+ and [L1{Ni(dppf)}2]2+ in an analogous fashion. In the same manner, reaction between [(L′2)(AuCl)2] (L′2 = dppm, dppf; dppm = bis(diphenylphosphino)methane) and KS2CN(Bz)CH2CH2N(Bz)CS2K yield [L1{Au2(L′2)}2]. The molecular structures of [L1{M(dppf)}2](PF6)2 (M = Ni, Pd) and [L1{Au(PR3)}2] (R = Me, Ph) are reported.

The new 2-phenylthiocarbamoyl-1,3-dimesitylimidazolium inner salt (IMes·CSNPh) reacts with [AuCl(L)] in the presence of NH4PF6 to yield [(L)Au(SCNPh·IMes)]+ (L = PMe3, PPh3, PCy3, CNBut). The carbene-containing precursor [(IDip)AuCl] reacts with IMes·CSNPh under the same conditions to afford the complex [(IDip)Au(SCNPh·IMes)]+ (IDip = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). Treatment of the diphosphine complex [(dppm)(AuCl)2] with one equivalent of IMes·CSNPh yields the digold metallacycle, [(dppm)Au2(SCNPh·IMes)]2+, while reaction of [L2(AuCl)2] with two equivalents of IMes·CSNPh results in [(L2){Au(SCNPh·IMes)}2]2+ (L2 = dppb, dppf, or dppa; dppb = 1,4-bis(diphenylphosphino)butane, dppf = 1,1′-bis(diphenylphosphino)ferrocene, dppa = 1,4-bis(diphenylphosphino)acetylene). The homoleptic complex [Au(SCNPh·IMes)2]+ is formed on reaction of [AuCl(tht)] (tht = tetrahydrothiophene) with two equivalents of the imidazolium-2-phenylthiocarbamoyl ligand. This product reacts with AgOTf to yield the mixed metal compound [AuAg(SCNPh·IMes)2]2+. Over time, the unusual trimetallic complex [Au(AgOTf)2(SCNPh·IMes)2]+ is formed. The sulfur-oxygen mixed-donor ligands IMes·COS and SIMes·COS (SIMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) were used to prepare [(L)Au(SOC·IMes)]+ and [(L)Au(SOC·SIMes)]+ from [(L)AuCl] (L = PPh3, CNtBu). The bimetallic examples [(dppf){Au(SOC·IMes)}2]2+ and [(dppf){Au(SOC·SIMes)}2]2+ were synthesized from the reaction of [(dppf)(AuCl)2] with the appropriate ligand. Reaction of [(tht)AuCl] with one equivalent of IMes·COS or SIMes·COS yields [Au(SOC·IMes)2]+ and [Au(SOC·SIMes)2]+, respectively. The compounds [(Ph3P)Au(SCNPh·IMes)]PF6, [(Cy3P)Au(SCNPh·IMes)]PF6 and [Au(AgOTf)2(SCNPh·IMes)2]OTf were characterized crystallographically.

The complex cis-[RuCl2(dppm)2] reacts with the amine-terminated dithiocarbamates KS2CN(CH2CH2NEt2)2 and KS2CN(CH2CH2CH2NMe2)2 to form the compounds [Ru{S2CN(CH2CH2NEt2)2}(dppm)2]+ and [Ru{S2CN(CH2CH2CH2NMe2)2}(dppm)2]+, respectively. The methoxy-terminated dithiocarbamate compound [Ru{S2CN(CH2CH2OMe)2}(dppm)2]+ was also prepared from the same precursor using KS2CN(CH2CH2OMe)2. The alkenyl complexes [RuRCl(CO)(BTD)(PPh3)2] (R = CHCHBut, CHCHC6H4Me-4, CHCHCPh2OH), [Ru(C(CCBut)CHBut)Cl(CO)(PPh3)2] and [Os(CHCHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] also react cleanly with KS2CN(CH2CH2CH2NMe2)2 and KS2CN(CH2CH2NEt2)2 to yield [MR{S2CN(CH2CH2CH2NMe2)2}(CO)(PPh3)2] and [MR{S2CN(CH2CH2NEt2)2}(CO)(PPh3)2], respectively. In a similar fashion, the compounds [RuR{S2CN(CH2CH2OMe2)2}(CO)(PPh3)2] (R = CHCHBut, CHCHC6H4Me-4, C(CCBut)CHBut) were also prepared. Treatment of [Ru(CHCHBut){S2CN(CH2CH2CH2NMe2)2}(CO)(PPh3)2] and [Ru{S2CN(CH2CH2NEt2)2}(dppm)2]+ with trifluoroacetic acid affords the ammonium complexes [Ru(CHCHBut){S2CN(CH2CH2CH2NHMe2)2}(CO)(PPh3)2]2+ and [Ru{S2CN(CH2CH2NHEt2)2}(dppm)2]2+, while the same reagent generates the tricationic vinylcarbene complex [Ru(CHCHCPh2){S2CN(CH2CH2CH2NHMe2)2}(CO)(PPh3)2]3+ through loss of water from [Ru(CHCHCPh2OH){S2CN(CH2CH2CH2NMe2)2}(CO)(PPh3)2]. The structures of [Ru{S2CN(CH2CH2OMe)2}(dppm)2]PF6 and [Ru(CHCHC6H4Me-4){S2CN(CH2CH2OMe)2}(CO)(PPh3)2] were determined crystallographically.

The palladium(II) dimer, [Pd(C,N-C6H4CH2NMe2)Cl]2 reacts with two equivalents of the NHC·CS2 zwitterionic ligands [NHC = IPr (1,3-diisopropylimidazol-2-ylidene), ICy (1,3-dicyclohexylimidazol-2-ylidene), IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IDip (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), SIMes (1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene)] in the presence of NH4PF6, to yield the cationic products [Pd(C,N-C6H4CH2NMe2)(S2C·NHC)]+. In a similar fashion, the compounds [Pd(C,N-bzq)(S2C·NHC)]+ (bzq = benzo[h]quinolinyl, NHC = ICy, IMes, IDip) are obtained from the corresponding dimer [Pd(C,N-bzq)Cl]2. The bis(phosphine) compounds [Pd(S2C·NHC)(PPh3)2]2+ (NHC = ICy, IMes, IDip, SIMes) are obtained on treatment of [PdCl2(PPh3)2] with NHC·CS2 zwitterions in the presence of NH4PF6. The reaction of [PdCl2(dppf)] with IMes·CS2 and NH4PF6 provides the complex [Pd(S2C·IMes)(dppf)]2+. The complexes [Pd(S2C·NHC)(PPh3)2](PF6)2 (NHC = IMes, IDip) were active pre-catalysts (1 mol% loading) for the conversion of benzo[h]quinoline to 10-methoxybenzo[h]quinoline in the presence of PhI(OAc)2 and methanol. The intermediacy of [Pd(C,N-bzq)(S2C·NHC)]+ was supported by the high yield of 10-methoxybenzo[h]quinoline using [Pd(C,N-bzq)(S2C·IDip)]+ to promote the same reaction. Small amounts of 2,10-dimethoxybenzo[h]quinoline were also isolated from these reactions. Using [Pd(C,N-bzq)(S2C·IDip)]+ and N-chlorosuccinimide as the oxidant led to the formation of 10-chlorobenzo[h]quinoline in moderate yield from benzo[h]quinoline. The molecular structures of [Pd(S2C·IMes)(PPh3)2](PF6)2 and [Pd(S2C·IMes)(dppf)](PF6)2 were determined crystallographically.

The ruthenium(II) complexes [Ru(R)(κ2-S2C·IPr)(CO)(PPh3)2]+ (R = CHCHBut, CHCHC6H4Me-4, C(CCPh)CHPh) are formed on reaction of IPr·CS2 with [Ru(R)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(CCPh)CHPh)Cl(CO)(PPh3)2] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CHCHC6H4Me-4)(κ2-S2C·ICy)(CO)(PPh3)2]+ and [Ru(C(CCPh)CHPh)(κ2-S2C·ICy)(CO)(PPh3)2]+ are formed in the same manner when ICy·CS2 is employed. The ligand IMes·CS2 reacts with [Ru(R)Cl(CO)(BTD)(PPh3)2] to form the compounds [Ru(R)(κ2-S2C·IMes)(CO)(PPh3)2]+ (R = CHCHBut, CHCHC6H4Me-4, C(CCPh)CHPh). Two osmium analogues, [Os(CHCHC6H4Me-4)(κ2-S2C·IMes)(CO)(PPh3)2]+ and [Os(C(CCPh)CHPh)(κ2-S2C·IMes)(CO)(PPh3)2]+ were also prepared. When the more bulky diisopropylphenyl derivative IDip·CS2 is used, an unusual product, [Ru(κ2-SC(H)S(CHCHC6H4Me-4)·IDip)Cl(CO)(PPh3)2]+, with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CHCHC6H4Me-4)Cl(BTD)(CO)(PPh3)2] also reacts with IMes·CS2 and NH4PF6 to yield the analogous product [Ru{κ2-SC(H)S(CHCHC6H4Me-4)·IMes}Cl(CO)(PPh3)2]+via the intermediate [Ru(CHCHC6H4Me-4)(κ2-S2C·IMes)(CO)(PPh3)2]+. Structural studies are reported for [Ru(CHCHC6H4Me-4)(κ2-S2C·IPr)(CO)(PPh3)2]PF6 and [Ru(C(CCPh)CHPh)(κ2-S2C·ICy)(CO)(PPh3)2]PF6.

Immobilised [Cu(NHC)] catalysts are reported for the preparation of 1,2,3-triazoles. In addition to showing outstanding catalytic activity, the catalyst systems are easy to prepare and can be recycled many times.