Eine Studie zur P₄-Umwandlung an niedervalenten Eisenkomplexen wird vorgestellt, bei der β-Diketiminato(L)-Fe^I-Komplexe vom Typ [LFe(tol)] (tol=Toluol; L=L¹ (1 a), L² (1 b), L³ (1 c)) mit unterschiedlichen Kombinationen von aromatischen und Rückgrat-Substituenten am Liganden genutzt werden. Die Produkte [(LFe)₄(μ₄-η²:η²:η²:η²-P₈)] (L=L¹ (2 a), L² (2 b)), die ein P₈-Gerüst enthalten, werden durch die Reaktion von 1 a,b mit P₄ in Toluol bei Raumtemperatur erhalten. Bei Verwendung eines etwas sperrigeren Liganden in 1 c wird [(L³Fe)₂(μ-η⁴:η⁴-P₄)] (2 c) gebildet, welches eine cyclo-P₄-Einheit enthält. Die Verbindungen 2 a–c wurden umfassend charakterisiert und ihre elektronische Struktur durch SQUID-Magnetisierung und ⁵⁷Fe-Mössbauer-Spektroskopie sowie mittels DFT-Methoden untersucht.

A study of P₄ transformations at low-valent iron is presented using β-diketiminato (L) Fe^I complexes [LFe(tol)] (tol=toluene; L=L¹ (1 a), L² (1 b), L³ (1 c)) with different combinations of aromatic and backbone substituents at the ligand. The products [(LFe)₄(μ₄-η²:η²:η²:η²-P₈)] (L=L¹ (2 a), L² (2 b)) containing a P₈ core were obtained by the reaction of 1 a,b with P₄ in toluene at room temperature. Using a slightly more sterically encumbered ligand in 1 c results in the formation of [(L³Fe)₂(μ-η⁴:η⁴-P₄)] (2 c), possessing a cyclo-P₄ moiety. Compounds 2 a–c were comprehensively characterized and their electronic structures investigated by SQUID magnetization and ⁵⁷Fe Mössbauer spectroscopy as well as by DFT methods.

A new and selective one-step synthesis was developed for the first activation stage of white phosphorus by organic radicals. The reactions of NaCp^R with P₄ in the presence of CuX or FeBr₃ leads to the clean formation of organic substituted P₄ butterfly compounds Cp^R₂P₄ (Cp^R: Cp^BIG=C₅(4-nBuC₆H₄)₅ (1 a), Cp′′′=C₅H₂tBu₃ (1 b), Cp*=C₅Me₅ (1 c) und Cp^4iPr=C₅HiPr₄ (1 d)). The reaction proceeds via the activation of P₄ by Cp^R radicals mediated by transition metals. The newly formed organic derivatives of P₄ have been comprehensively characterized by NMR spectroscopy and X-ray crystallography.

Reactions of the sandwich complexes [Cp*Fe(η⁵-E₅)] (Cp*=η⁵-C₅Me₅; E=P (1), As (2)) with the monovalent Group 13 metals Tl⁺, In⁺, and Ga⁺ containing the weakly coordinating anion [TEF] ([TEF]=[Al{OC(CF₃)₃}₄]⁻) are described. Here, the one-dimensional coordination polymers [M(μ,η⁵:η¹-E₅FeCp*)₃]_n[TEF]_n (E=P, M=Tl (3 a), In (3 b), Ga (3 c); E=As, M=Tl (4 a), In (4 b)) are obtained as sole products in good yields. All products were analyzed by single-crystal X-ray diffraction, revealing a similar assembly of the products with η⁵-bound E₅ ligands and very weak σ-interactions between one P or As atom of the ring to the neighbored Group 13 metal cation. By exchanging the [TEF] anion of 4 a for the larger [FAl] anion ([FAl]=[FAl{OC₆F₁₀(C₆F₅)}₃]⁻), the coordination compound [Tl{(η⁵-As₅)FeCp*}₃][FAl] (5) without any σ-interactions of the As₅-ring is obtained. All products are readily soluble in CH₂Cl₂ and exhibit a dynamic coordination behavior in solution, which is supported by NMR spectroscopy and ESI-MS spectrometry as well as by osmometric molecular-weight determination. For a better understanding of the proceeding equilibrium DFT calculations of the cationic complexes were performed for the gas phase and in solution. Furthermore, the ³¹P{¹H} magic-angle spinning (MAS) NMR spectra of 3 a–c are presented and the first crystal structure of the starting material 2 was determined.

Slow diffusion reactions of the pentaphosphaferrocene [Cp*Fe(η⁵-P₅)] (Cp*=η⁵-C₅Me₅ (1)) with CuX (X=Cl, Br, I) in different stoichiometric ratios and solvent mixtures result in the formation of one- and two-dimensional polymeric compounds 2–6 with molecular formula [{Cu(μ-X)}{Cp*Fe(μ₃,η⁵:η¹:η¹-P₅)}]_n (X=Cl (2 a), I (2′c)), [{Cu(μ-I)}{Cp*Fe(μ₃,η⁵:η¹:η¹-P₅)}]_n (3), [{CuX}{Cp*Fe(μ₄,η⁵:η¹:η¹:η¹-P₅)}]_n (X=Cl (4 a), Br (4 b), I (4 c), Br (4′b), I (4′c)), [{Cu₃(μ-I)₂(μ₃-I)}{Cp*Fe(μ₅,η⁵:η¹:η¹:η¹:η¹-P₅)}]_n (5) and [{Cu₄(μ-X)₄(CH₃CN)}{Cp*Fe(μ₇,η⁵:η²:η¹:η¹:η¹:η¹:η¹-P₅)}]_n (X=Cl (6 a), Br (6 b)), respectively. The polymeric compounds have been characterised by single-crystal X-ray diffraction analyses and, for selected examples, by magic angle spinning (MAS) NMR spectroscopy. The solid-state structures demonstrate the versatile coordination modes of the cyclo-P₅ ligand of 1, extending from two to five coordinating phosphorus atoms in either σ or σ-and-π fashion. In compounds 2 a, 2′c and 3, two phosphorus atoms of 1 coordinate to copper atoms in a 1,2 coordination mode (2 a, 2′c) and an unprecedented 1,3 coordination mode (3) to form one-dimensional polymers. Compounds 4 a–c, 4′b, 4′c and 5 represent two-dimensional coordination polymers. In compounds 4, three phosphorus atoms coordinate to copper atoms in a 1,2,4 coordination mode, whereas in 5 the cyclo-P₅ ligand binds in an unprecedented 1,2,3,4 coordination mode. The crystal structures of 6 a,b display a tilted tube, in which all P atoms of the cyclo-P₅ ligand are coordinated to copper atoms in σ- and π-bonding modes.

Treatment of the pentaphosphaferrocene [Cp*Fe(η⁵-P₅)] with Cu^I halides in the presence of different templates leads to novel fullerene-like spherical molecules that serve as hosts for the templates. If ferrocene is used as the template the 80-vertex ball [Cp₂Fe]@[{Cp*Fe(η⁵-P₅)}₁₂{CuCl}₂₀] (4), with an overall icosahedral C₈₀ topological symmetry, is obtained. This result shows the ability of ferrocene to compete successfully with the internal template of the reaction system [Cp*Fe(η⁵-P₅)], although the 90-vertex ball [{Cp*Fe(η⁵:η¹:η¹:η¹:η¹:η¹-P₅)}₁₂(CuCl)₁₀(Cu₂Cl₃)₅{Cu(CH₃CN)₂}₅] (2 a) containing pentaphosphaferrocene as a guest is also formed as a byproduct. With use of the triple-decker sandwich complex [(CpCr)₂(μ,η⁵-As₅)] as a template the reaction between [Cp*Fe(η⁵-P₅)] and CuBr leads to the 90-vertex ball [(CpCr)₂(μ,η⁵-As₅)]@[{Cp*Fe(η⁵-P₅)}₁₂{CuBr}₁₀{Cu₂Br₃}₅{Cu(CH₃CN)₂}₅] (6), in which the complete molecule acts as a template. However, if the corresponding reaction is instead carried out with CuCl, cleavage of the triple-decker complex is found and the 80-vertex ball [CpCr(η⁵-As₅)]@[{Cp*Fe(η⁵-P₅)}₁₂{CuCl}₂₀] (5) is obtained. This accommodates as its guest [CpCr(η⁵-As₅)], which has only 16 valence electrons in a triplet ground state and is not known as a free molecule. The triple-decker sandwich complex [(CpCr)₂(μ,η⁵-As₅)] requires 53.1 kcal mol⁻¹ to undergo cleavage (as calculated by DFT methods) and therefore this reaction is clearly endothermic. All new products have been characterized by single-crystal X-ray crystallography. A favoured orientation of the guest molecules inside the host cages has been identified, which shows π⋅⋅⋅π stacking of the five-membered rings (Cp and cyclo-As₅) of the guests and the cyclo-P₅ rings of the nanoballs of the hosts.

The coordination behavior of 1,2,4-triphosphaferrocenes [FeCp^R(η⁵-P₃C₂tBu₂)] [Cp^R = Cp (1), Cp″′ = η⁵-C₅H₂tBu₃ (3)] towards Cu^I halides is significantly influenced by the substitution pattern of the cyclopentadienyl ring attached to the iron atom. The reaction of the Cp derivative 1 with CuBr in a 1:1 stoichiometry leads to the dimeric complex [{FeCp(η⁵:η¹:η¹-P₃C₂tBu₂)}{μ-CuBr(MeCN)}]₂ (5b), in which two 1,2,4-triphosphaferrocenes are linked by two CuBr units. By using a 1:2 stoichiometry, the 1D polymeric compound [{FeCp(η⁵:η¹:η¹:η¹-P₃C₂tBu₂)}μ-{(CuBr)₃(MeCN)₂}]_n (6) is formed in which the triphosphaferrocenes are bridged by (CuBr)₂{CuBr(MeCN)₂} units. Starting from CuI, independent of the stoichiometry, the cage compound [{FeCp(η⁵:η¹:η¹-P₃C₂tBu₂)}₃{Cu(μ-I)}₃{Cu(μ₃-I)}₃{Cu(NCMe)}(μ₆-I)](7) is formed. However, if the bulky Cp″′ derivative 3 is used already in a 1:1 stoichiometry with CuBr, a transformation of the initially five-membered 1,2,4-triphospholyl ring into a four-membered 1,2-diphosphete ligand is observed, which is linked by CuBr moieties forming the dimeric paramagnetic complex [{FeCp″′(η⁴:η¹:η¹-P₂C₂tBu₂)}(μ-CuBr)]₂ (9). Furthermore, applying a 1:2 stoichiometry between 3 and CuX (X = Br, I) the complete fragmentation of the 1,2,4-triphospholyl ring under mild conditions into a tetraphosphabutadiene ligand is observed. In the formed 1D polymeric complexes [{(FeCp″′)₂(μ,η⁴:η¹:η¹-P₄)}{(μ-CuX)₂(MeCN)}]_n [X = Br (10a), I (10b)] this ligand represents now the middle deck of the triple-decker sandwich complexes linked by four-membered [(CuX)₂(CH₃CN)] moieties. Moreover, the reaction of the Cp derivative 1 with the Ag salt of the weakly coordinating anion [Al{OC(CF₃)₃}]₄^– leads to the dimeric Ag(CH₃CN)-bridged dicationic product [{FeCp(η⁵-P₃C₂tBu₂)}Ag(MeCN)]₂[Al{OC(CF₃)₃}₄]₂ (11).

The reaction of the [{CpMo(CO)₂}₂(μ,η²:η²-P₂)] (Cp=cyclopentadienyl) metallo-ligand 2 with pre-organized Cu^I bi- and trimetallic precursors afforded new coordination complexes with unprecedented coordination modes for a Mo₂P₂ complex. Variable-temperature solution and solid-state ³¹P NMR spectroscopy measurements were performed and X-ray diffraction studies revealed an η²:η¹ coordination mode for the Mo₂P₂ unit of 2 in the Cu^I bimetallic complexes 3 and 4. DFT calculations were carried out to highlight the bonding situation of this unprecedented coordination mode in the Cu^I bimetallic compound 3. It is built up from a side-on coordination of the PP σ bond to one copper ion and from the interaction of the lone pair of one phosphorus atom with the second copper ion. The remaining available lone pair of the second phosphorus atom can be involved as well to interact with an additional metal centre, as evidenced in the Cu^I trimetallic compound 5 in which an η²:η¹:η¹ coordination mode of the ligand 2 is observed. Derivative 3 can be used as a molecular clip to obtain discrete π-stacked dimers through a ligand exchange reaction between acetonitrile ligands and cyano-capped π-conjugated systems, indicating the stability of the new η²:η¹ coordination mode.

Photolysis of [Cp*As{W(CO)₅}₂] (1 a) in the presence of Mes*PPMes* (Mes*=2,4,6-tri-tert-butylphenyl) leads to the novel 1,3-diphospha-2-arsaallyl radical [(CO)₅W(μ,η²:η¹-P₂AsMes*₂)W(CO)₄] (2 a). The frontier orbitals of the radical 2 a are indicative of a stable π-allylic system that is only marginally influenced by the d orbitals of the two tungsten atoms. The SOMO and the corresponding spin density distribution of the radical 2 a show that the unpaired electron is preferentially located at the two equivalent terminal phosphorus atoms, which has been confirmed by EPR spectroscopy. The protonated derivative of 2 a, the complex [(CO)₅W(μ,η²:η¹-P₂As(H)Mes*₂)W(CO)₄] (6 a) is formed during chromatographic workup, whereas the additional products [Mes*PPMes*{W(CO)₅}] as the Z-isomer (3) and the E-isomer (4), and [As₂{W(CO)₅}₃] (5) are produced as a result of a decomposition reaction of radical 2 a. Reduction of radical 2 a yields the stable anion [(CO)₅W(μ,η²:η¹-P₂AsMes*₂)W(CO)₄]⁻ in 7 a, whereas upon oxidation the corresponding cationic complex [(CO)₅W(μ,η²:η¹-P₂AsMes*₂)W(CO)₄][SbF₆] (8 a) is formed, which is only stable at low temperatures in solution. Compounds 2 a, 7 a, and 8 a represent the hitherto elusive complexed redox congeners of the diphospha-arsa-allyl system. The analogous oxidation of the triphosphaallyl radical [(CO)₅W(μ,η²:η¹- P₃Mes*₂)W(CO)₄] (2 b) also leads to an allyl cation, which decomposes under CH activation to the phosphine derivative [(CO)₅W{μ,η²:η¹-P₃(Mes*)(C₅H₂tBu₂C(CH₃)₂CH₂)}W(CO)₄] (9), in which a CH bond of a methyl group of the Mes* substituent has been activated. All new products have been characterized by NMR spectrometry and IR spectroscopy, and compounds 2 a, 3, 6 a, 7 a, and 9 by X-ray diffraction analysis.

Thermolysis of [Cp*P{W(CO)₅}₂] (1) in the presence of [{CpMo(CO)₂}₂] leads to the novel complexes [{(CO)₂Cp*W}{CpMo(CO)₂}(μ,η²:η¹:η¹-P₂{W(CO)₅}₂)] (6; Cp=η⁵-C₅H₅, Cp*=η⁵-C₅Me₅), [{(μ-O)(CpMoWCp*)W(CO)₄}{μ₃-PW(CO)₅}₂] (7), [{CpMo(CO)₂}₂{Cp*W(CO)₂}{μ₃-PW(CO)₅}] (8) and [{CpMo(CO)₂}₂{Cp*W(CO)₂}(μ₃-P)] (9). The structural framework of the main products 8 and 9 can be described as a tetrahedral Mo₂WP unit that is formed by a cyclisation reaction of [{CpMo(CO)₂}₂] with an [Cp*(CO)₂WPW(CO)₅] intermediate containing a WP triple bond and subsequent metal–metal and metal–phosphorus bond formation. Photolysis of 1 in the presence of [{CpMo(CO)₂}₂] gives 8, 9 and phosphinidene complex [(μ₃-PW(CO)₅){CpMo(CO)₂W(CO)₅}] (10), in which the P atom is in a nearly trigonal-planar coordination environment formed by one {CpMo(CO)₂} and two {W(CO)₅} units. Comprehensive structural and spectroscopic data are given for the products. The reaction pathways are discussed for both activation procedures, and DFT calculations reveal the structures with minimum energy along the stepwise Cp* migration process under formation of the intermediate [Cp*(CO)₂WPW(CO)₅].

Reaction of complex [Cp₂Mo₂(CO)₄(μ,η²-P₂)] (Cp=C₅H₅ (1)) with CuPF₆, AgX (X=BF₄, ClO₄, PF₆, SbF₆, Al{OC(CF₃)₃}₄) and [(Ph₃P)Au(THF)][PF₆] (THF=tetrahydrofuran), respectively, results in the facile formation of the dimers 3 b–h of the general formula [M₂({Cp₂Mo₂ (CO)₄(μ,η²:η²-P₂)}₂)({Cp₂Mo₂(CO)₄ (μ,η²:η¹:η¹-P₂)}₂)][X]₂ (M=Cu, Ag, Au; X=BF₄, ClO₄, PF₆, SbF₆, Al{OC(CF₃)₃}₄). As revealed by X-ray crystallography, all these dimers comprise dicationic moieties that are well-separated from the weakly coordinating anions in the solid state. If 1 is allowed to react with AgNO₂ and LAuCl (L=CO or tetrahydrothiophene), respectively, the dimer [Ag₂{Cp₂Mo₂ (CO)₄(μ,η²:η¹:η¹-P₂)}₂(η²-NO₂)₂] (5) and the complex [AuCl{Cp₂Mo₂(CO)₄(μ,η²:η¹-P₂)}] (6) are formed, which have also been characterised by X-ray crystallography. In compounds 5 and 6, the anions remain coordinated to the Group 11 metal centres. Spectroscopic data suggest that the dimers 3 b–h display dynamic behaviour in solution and this is discussed by using the comprehensive results obtained for 3 g (M=Ag; X=Al{OC(CF₃)₃}₄) as a basis. The interpretation of the experimental results is facilitated by density functional theory (DFT) calculations on 3 g (structures, energetics, NMR shielding tensors). The ³¹P magic angle spinning (MAS) NMR spectra recorded for the dimers 3 b (M=Cu; X=PF₆) and 3c (M=Ag; X=BF₄) as well as that of the previously reported one-dimensional (1 D) polymer [Ag₂{Cp₂Mo₂(CO)₄(μ,η²:η¹:η¹-P₂)}₃(μ,η¹:η¹-NO₃)]_n[NO₃]_n (4) are also discussed herein and the strong dependence of the chemical shift of the phosphorus atoms within each compound on subtle structural differences in the solid state is demonstrated. Furthermore, the X-ray crystallographic and ³¹P MAS NMR spectroscopic characterisation of a new polymorph of 1 is reported.