The preparation and molecular structure oftrans-[MoCl2(PMe2Ph)4]

Summary The compoundtrans-[MoCl₂(PMe₂Ph)₄] has been prepared by the reduction of MoCl₅ (by Mg) or of [MoCl₃(PMe₂Ph)₃] (by LiBuⁿ) in the presence of PMe₂Ph in tetrahydrofuran (THF). It has _eff=2.84 B.M. and crystallises in space group P1 witha=11.591(3),b=12.931(3),c=12.703(3) Å, = 95.28(2), =105.97(2), =103.54(2)°. Refinement of the structure gave R=0.036. The Mo-Cl and Mo-P distances average 2.443(6) and 2.534(8) Å, respectively.Low-valent phosphine complexes of the Group VI metals continue to attract much attention because of their involvement in studies of the catalytic activation of dinitrogen⁽¹⁾, dihydrogen(^{2, 3}), alkenes and alkynes(⁴). As a by-product during our studies of dinitrogen(¹) and hydride(²) complexes of molybdenum and tungsten, we obtainedtrans-[MoCl_2- (PMe₂Ph)₄] as yellow, paramagnetic crystals (_eff= 2.84 B.M.). We first obtained the compound during the attempted synthesis ofcis-[Mo(N₂)₂(PMe₂Ph)₄] by reduction of MoCl₅ with Mg in the presence of PMe₂Ph (see Experimental). Upon identification of the compound we found that it could be readily synthesised by treatment of [MoCl₃(PMe₂Ph)₃]⁽⁵⁾ with LiBuⁿ in THF in the presence of PMe₂Ph (experimental).The complex was shown to have thetrans structure by x-ray analysis (Figure). Analogues oftrans-[MoCl₂(PMe₂Ph)₄] have been prepared, namely [CrCl₂(Me₂PCH₂CH₂PMe₂)₂]⁽⁶⁾,trans- [MoCl₂(PMe₃)₄]⁽⁷⁾, [WCl₂(PMe₂Ph)₄]⁽⁸⁾ and [WCl₂(PMe₃)₄]⁽⁴⁾, of which onlytrans-[MoCl₂(PMe₃)₄] has been examined by X-rays⁽⁷⁾. Its principal structural parametersi.e. d(Mo-Cl)= 2.420(6), d(Mo-P)_av=2.496(3) Å⁽⁶⁾ are close to those found here fortrans-[MoCl₂(PMe₂Ph)₄].     

Electroanalytical study of the kinetics of thefac-mer isomerization of [ReCl(CO)3(PMe2Ph)2]+ in acetonitrile

Summary The isomerization offac-[ReCl(CO)₃(PMe₂Ph)₂]⁺ to the corresponding meridional-trans isomer has been studied by electroanalytical techniques in MeCN solvent. Chronoamperometric and cyclic voltammetric data relative to the oxidation offac- andmer-[ReCl(CO)₃(PMe₂Ph)₂] allow the accurate determination of the very high kinetic rate constant for the isomerization and permit discussion of thermodynamic aspects of redox homogeneous chemical reactions involving species of the different redox couples arising from the anodic processes.     

Synthese und Kristallstrukturen der mehrkernigen Rhenium–Nitrido‐Komplexe [Re2N2Cl4(PMe2Ph)4(MeCN)] und [Re4N3Cl9(PMe2Ph)6]

Synthesis and Structures of the Multinuclear Rhenium Nitrido Complexes [Re₂N₂Cl₄(PMe₂Ph)₄(MeCN)] and [Re₄N₃Cl₉(PMe₂Ph)₆] The binuclear rhenium complex [Re₂N₂Cl₄(PMe₂Ph)₄(MeCN)] ( 1 ) is obtained as a byproduct of the synthesis of [(Me₂PhP)₃(MeCN)ClReNZrCl₅] from [ReNCl₂(PMe₂Ph)₃] and [ZrCl₄(MeCN)₂] in toluene. It crystallizes as 1 · 2 toluene in the monoclinic space group P2₁/n with a = 1517.0(3); b = 1847.7(2); c = 1952.4(6) pm; β = 106.44(1)° and Z = 4. The two Re atoms are connected by an asymmetric nitrido bridge Re≡N–Re with distances Re–N of 169.9(5) and 208.7(5) pm. In course of the reaction of [ReNCl₂(PMe₂Ph)₃] with [ZrCl₄(THF)₂] in CH₂Cl₂ hydrochloric acid is formed by acting of the Lewis acid on the solvent. HCl protonates and eliminates phosphine ligands of the educt [ReNCl₂(PMe₂Ph)₃] to form the phosphonium salt [PMe₂PhH]₂[ZrCl₆] ( 2 ). It crystallizes in the monoclinic space group C2/c with a = 1536.9(3); b = 1148.8(1); c = 1402.2(3) pm, β = 100.70(2)° and Z = 4. The remaining fragments of the rhenium complex combine to yield the tetranuclear mixed valent complex [Re₄N₃Cl₉(PMe₂Ph)₆] ( 3 ), crystallizing as 3 · CH₂Cl₂ in the triclinic space group P 1 with a = 1312.9(19); b = 1661.4(2); 1897.1(2) pm; α = 78.62(1)°; β = 86.77(1)°; γ = 68.28(1)° and Z = 2. The four Re atoms occupy the corners of a tetrahedron. Its edges are formed by three nitrido and three chloro bridges. The asymmetric nitrido bridges Re≡N–Re are characterized by short distances in the range of 172(2) to 176(3) pm and long distances of 194(3) to 204(2) pm. The angles Re–N–Re are between 154(1) and 160(1)°.     

Preparation and properties of dinitrogen complexes of molybdenum and tungsten with trimethylphosphine as coligand : III. Synthesis and properties of cis-[W(N2)2(PMe3)4], trans-[W(C2H4)2(PMe3)4] and [M(N2)(PMe3)5] (M = Mo,W). The crystal and molecular structure of [Mo(N2)(PMe3)5]

The reduction of [WCl₄(PMe₃)₃] with dispersed sodium, under dinitrogen, gives cis-[W(N₂)₂(PMe₃)₄], while under ethylene trans-[W(C₂H₄)₂(PMe₃)₄] is obtained. The ethylene complex can also be prepared by displacement of the dinitrogen molecules in cis-[W(N₂)₂(PMe₃)₄] by ethylene at room temperature and pressure. Interaction of cis-[M(N₂)₂(PMe₃)₄] complexes (M = Mo, W), with PMe₃, under helium or argon, yields [M(N₂)(PMe₃)₅]. The molybdenum complex crystallizes in the orthorhombic space group Pnma, with a 22.063(6), b 12.106(4), c 9.745(4) Å. The Mo—P distance trans to the dinitrogen ligand (2.483(7) Å) is slightly longer than the average of the other four Mo—P bonds (2.460(5) Å).     

Synthese und Struktur von [Re(NH)Cl2(PMe2Ph)3][TaCl6] und [(Me2PhP)3Cl2Re≡N]2VOCl2

Synthesis and Structure of [Re(NH)Cl₂(PMe₂Ph)₃][TaCl₆] and [(Me₂PhP)₃Cl₂Re≡N]₂VOCl₂ The products of the reaction of ReNCl₂(PMe₂Ph)₃ with TaCl₅ are dependent on the solvent. In CH₂Cl₂ the solvent protonates the nitrido ligand to yield [Re(NH)Cl₂(PMe₂Ph)₃][TaCl₆] as air-stable, reddish brown needles with the space group P2₁/n and a = 1213.8(3), b = 1358.0(2), c = 2165.9(4) pm, β = 92.88(1)°, Z = 4. The Re atom of the cation exhibits an octahedral coordination with the phosphine ligands in meridional arrangement. The imido ligand is in trans-position to a Cl atom with a distance Re–N = 170.4(4) pm. When the reaction is carried out in toluene the dinuclear nitrido complex [Re(NTaCl₅)Cl₂(PMe₂Ph)₃] is obtained instead. The reaction of ReNCl₂(PMe₂Ph)₃ with VCl₃(THF)₃ in toluene affords the threenuclear complex [Re₂N₂Cl₄(PMe₂Ph)₅]VCl₃, which upon crystallization at air gives air-stable, reddish-brown crystals of [(Me₂PhP)₃Cl₂ReN]₂VOCl₂. They crystallize in the monoclinic space group P2₁ with a = 1519.2(5), b = 1257.1(1), c = 1564.3(6) pm, β = 102.86(2)°, and Z = 2. The threenuclear complex shows an almost linear arrangement Re≡N–V–N≡Re with distances Re–N 171(2) pm and V–N of 209(2) pm.     

Hydrido-silyl complexes,Part VIII. Photochemical reaction of [Fe(CO)3H(PR′3)SiR3] with silanes,HSiR3: Influence of PR′3 and SiR3 on formation and structures of bis-silyl complexes [Fe(CO)3(PR′3)(SiR3)2]

Summary Upon u.v. irradiation of [Fe(CO)₄(PR ₃ )] with HSiR₃ (HSiR₃ = HSiMePh₂, PR₃ = PPh₃; HSiR₃ = HSiMe₂Cl, PR₃ = PPh₃ or PMe₂Ph; HSiR₃ = HSiMeCl₂, PR₃ = PPh₃, PMePh₂, PMe₂Ph or PMe₃; HSiR₃ = HSiCl₃, PR₃ = PPh₃, PMePh₂, PMe₂Ph, PMe₃ or PBu ₃ ⁿ ) the corresponding hydridosilyl complexes [Fe(CO)₃H(PR₃)SiR₃] are formed. The complexes have themer configuration with acis disposition of the hydride and the silyl ligands. Prolonged irradiation with an excess of silane results in the formation of bis-silyl complexes [Fe(CO)₃(PR₃)(SiR₃)₂], if electron density at the metal is not too high. Thus, [Fe(CO)₃H(PPh₃)SiMePh₂] and [Fe(CO)₃-H(PMe₂Ph)SiMe₂Cl] can be obtained but not the corresponding bis-silyl complexes. Most bis-silyl complexes are obtained asmer-isomers with acis-arrangement of the silyl ligands. Only for [Fe(CO)₃(PR₃)(SiCl₃)₂] with small phosphine ligands (PR₃ = PMe₃ or PMe₂Ph) is thefac-isomer formed.Part VII of this series, ref. (1).     

The reaction between [Pt(cod)Cl(PMe2Ph)]BF4 and aryltrimethyltin compounds

The complex [Pt(cod)Cl(PMe₂Ph)]BF₄ reacts in dichloromethane with SnArMe₃ compounds having Ar = 2-thienyl, 2-benzol [b]thienyl, or 2-benzo[b]furyl to give air-stable cationic aryl complexes [Pt(cod)Ar(PMe₂Ph)]BF₄. No reaction takes place when Ar  Ph. The cod ligand in the new complexes can be readily replaced by ligands such as PMe₂Ph, dppe, or 4-dimethylaminopyridine. The¹H and³¹P-{¹H} NMR parameters of the various complexes are reported.     

Reactions of pentaborane(9) with electron-rich molybdenum and tungsten phosphine polyhydrides

Reaction of [W(PMe₂Ph)₃H₆] with pentaborane(9) gives nido-2-[W(PMe₂Ph)₃H₂B₄H₈] (1) as well as nido-2-[W(PMe₂Ph)₃HB₅H₁₀] (2). The crystal structure of (2) has been determined. Compound (2) has a novel metallaborane structure containing an edge-bridging {BH₃} group between the tungsten atom and one of the basal boron atoms in a “nido-WB₄” pyramid. Reaction of [W(PMe₃)₄(η²-CH₂PMe₂)H] with pentaborane(9) gives nido-2-[W(PMe₃)₃H₂B₄H₈] (3) whilst reaction of [Mo(L)₄H₄] with pentaborane(9) gives nido-2-[Mo(L)₃H₂B₄H₈] [L = PMe₃ (4), PMe₂Ph (5)]. Treatment of [Mo(PMe₃)₄H₄] with excess BH₃ · thf gives the known borohydride [Mo(PMe₃)₄H(η²-BH₄)].     

Preparation and properties of dinitrogen trimethylphosphine complexes of molybdenum and tungsten—II: Synthesis and crystal structures of [MCl(N2)(PMe3)4] (M = Mo,W) and trans-[MoCl2(PMe3)4]

Sodium amalgam reduction of the complexes [MCl₃(PMe₃)₃] (M = Mo, W) in tetrahydrofuran, under dinitrogen, yields dark red-brown suspensions from which red-orange crystals of composition trans-[MCl(N₂)· (PMe₃)₄] can be collected. Spectroscopic and chemical evidence indicate the compounds are best formulated as mixtures of trans-[M(N₂)₂(PMe₃)₄] and trans-[MCl₂(PMe₃)₄] species, but attempts to isolate the pure bis(dinitro derivatives have proved unsuccessful. Single crystals of analytical composition [MCl(N₂)(PMe₃)₄] have been studied by X-ray crystallography, and the structure of trans-[MoCl₂(PMe₃)₄] has been determined for comparison. trans-[MCl(N₂)(PMe₃)₄] (M = Mo, W) and trans-[MoCl₂(PMe₃)₄] are all isostructural, crystallizing in the tetragonal space group I$\text{4}$2 trans-[MoCl(N₂)(PMe₃)₄] has a = 9.597(5), b = 12.294(6) Å, D_c = 1.36g cm^?3 Z = 2 and was refined to a final R value of 0.021 based on 319 independent observed reflections. The tungsten analogue has a = 9.573(4), b = 12.278(5) Å, D_c = 1.63g cm^?3 for Z = 2 and was refined to R = 0.19 with 322 independent observed reflections. trans-[MoCl₂(PMe₃)₄] has cell parameters a = 9.675(5), b = 12.311(6) Å D_c = 1.36 g cm^?3 for Z = 2 and was refined to R = 0.043 with 316 independent observed reflections. In each case the metal atom resides on a crystallographic $\text{4}$2m position. For trans-[MoCl(N₂)(PMe₃)₄] (M = Mo, W) the chlorine and dinitrogen ligands are disordered. M-N distances of 2.08(1) ? (M = Mo) and 2.04(2) ? (M = W) and M-Cl bond lengths of 2.415(8) Å (M = Mo) and 2.46(1) Å (M = W) are observed. In trans-[MoCl₂(PMe₃)₄], where there is no disorder, the Mo-Cl distance is 2.420(6) Å.     

[{ReN(PMe2Ph)3}{ReO3N}]2 – Structural Evidence for the Nitridotrioxorhenate(VII) Anion, [ReO3N]2−

Air‐stable, orange‐red single crystals of [{ReN(PMe₂Ph)₃}{ReO₃N}]₂ are formed when mer‐[ReNCl₂(PMe₂Ph)₃] reacts with strong bases in MeOH. The resulting centrosymmetric tetranuclear complex contains each two {ReN(PMe₂Ph)₃}²⁺ and {ReO₃N}^2? building blocks. They are connected by two oxygen and two nitrogen atoms giving an almost planar {Re₄O₂N₂} ring. The Re–N–Re bridges are only slightly bent (175.2(2)°), while the Re–O–Re angles are 160.9(1)°. The coordination environment of the rhenium atom in the nitridotrioxorhenate(VII) anion is a slightly distorted tetrahedron with O–Re–O and O–Re–N angles between 108.7(1)° and 111.3(1)°.     

[PMe3(CH2CH(OMe)Ph)]+ A PHOSPHONIUM SALT WITH AN ASYMMETRIC CARBON ATOM SYNTHESIZED BY REACTION OF PHENYLACETYLENE WITH COBr(PMe3)3 IN METHANOL. STRUCTURAL CHARACTERIZATION

Abstract

Reaction of HC[tbnd]CPh in excess with a mixture of CoBr(PMe₃)₃/NaBPh₄ in methanol gave rise in 40% yield to the cationic phosphonium salt [PMe₃(CH₂CH(OMe)Ph)]BPh₄. It has been characterized in the solid state by X-ray diffraction and in solution by ¹H and ³¹P NMR.     

Reactions of ReH3(CO)(PMe2Ph)3 with Metallic Lewis Acids. Synthesis and Structural Characterization of Hydrido-Bridged Heterometallic Rhenium-Gold, Rhenium-Silver, and Rhenium-Copper Complexes

This contribution presents a study of the reactions of ReH₃(CO)(PMe₂Ph)₃ (1) with a variety of metallic Lewis acids of the coinage metals to form hydrido-bridged heterometallic rhenium-gold, rhenium-silver, and rhenium-copper complexes. The reaction of 1 with AuCl(PPh₃) proceeds with elimination of hydrogen to give the hydrido-bridged heterobinuclear rhenium-gold complex (PMe₂Ph)₃(CO)ClRe(-H)Au(PPh₃) (2). In contrast, the reactions of 1 with AgPF₆, [Cu(CH₃CN)₄]PF₆ or CuCl proceed without elimination of hydrogen to give the hydrido-bridged heterotrinuclear rhenium-silver and rhenium-copper complexes [(PMe₂Ph)₃(CO)HRe(-H)₂M(-H)₂ReH(CO)(PMe₂Ph)₃]PF₆ (M=Ag (3), Cu (4)) and the hydrido-bridged heterotetranuclear rhenium-copper complex (PMe₂Ph)₃(CO)HRe(-H)₂Cu(-Cl)₂Cu(-H)₂ReH(CO)(PMe₂Ph)₃ (5), respectively. The molecular structures of compounds 2 and 3 have been determined by single-crystal X-ray diffraction studies. Crystallographic data for 2: monoclinic, space group P2₁2₁2₁, a=12.804(2) Å, b=13.512(2) Å, c=24.312(3) Å, V=4206(1) ų, Z=4, and R=0.042. Crystallographic data for 3: monoclinic, space group C2/c, a=24.212(6) Å, b=13.098(3) Å, c=20.177(5) Å, b=116.40(2)°, V=5732(2) ų, Z=4, and R=0.044. The X-ray crystal structure of 2 exhibits a short contact (2.798(12) Å) between the gold atom and the CO ligand that is primarily bound to the adjacent rhenium atom, suggesting an incipient semibridging relationship.     

Phosphine carbonyl-technetium(I) and -technetium(III) complexes

Treatment of trans-[TcX₄L₂] (X Cl, Br and L PPH₃, PMe₂Ph) with carbon monoxide (1 atm) in boiling ethyleneglycol methyl ether, gives trans-[TcX-(CO)₃L₂]. Under these conditions the mer-[TcX₃(PMe₂Ph)₃] (X Cl, Br) gives a mixture of the trans-[TcX(CO)₃(PMe₂Ph)₂] and cis-[TcX(CO)₂(PMe₂Ph)₃] complexes, but when added free dimethylphenylphosphine is present only the second product is obtained. Carbon monoxide reacts with mer-[TcCl₃(PMe₂Ph)₃] in refluxing ethanol to give [TcCl₃(CO)(PMe₂Ph)₃] a C_{3 v} seven-coordinate technetium(III) complex.The stereochemistry of the complexes was determined from their IR and¹H NMR spectra.     

Synthesis and spectroscopy of cis-configured mononuclear palladium(II) and platinum(II) complexes of chalcogeno o-carboranes and structures of [Pt(SCboPh)2(dppm)], [Pt(SeCboPh)2(dppm)], [Pt(SCboS)(PMe2Ph)2] and [Pt(SCboS)(PMePh2)2]

The reactions of [MCl₂(P^∩P)] and [MCl₂(PR₃)₂)] with 1-mercapto-2-phenyl-o-carborane/NaSeCb^oPh and 1,2-dimercapto-o-carborane yield mononuclear complexes of composition, [M(SCb^oPh)₂(P^∩P)], [M(SeCb^oPh)₂(P^∩P)] (M = Pd or Pt; P^∩P = dppm (bis(diphenylphosphino)methane), dppe (1,2-bis(diphenylphosphino)ethane) or dppp (1,3-bis(diphenylphosphino)propane)) and [M(SCb^oS)(PR₃)₂] (2PR₃ = dppm, dppe, 2PEt₃, 2PMe₂Ph, 2PMePh₂ or 2PPh₃). These complexes have been characterized by elemental analysis and NMR (¹H, ³¹P, ⁷⁷Se and ¹⁹⁵Pt) spectroscopy. The ¹J(Pt–P) values and ¹⁹⁵Pt NMR chemical shifts are influenced by the nature of phosphine as well as thiolate ligand. Molecular structures of [Pt(SCb^oPh)₂(dppm)], [Pt(SeCb^oPh)₂(dppm)], [Pt(SCb^oS)(PMe₂Ph)₂] and [Pt(SCb^oS)(PMePh₂)₂] have been established by single crystal X-ray structural analyses. The platinum atom in all these complexes acquires a distorted square planar configuration defined by two cis-bound phosphine ligands and two chalcogenolate groups. The carborane rings are mutually anti in [Pt(SCb^oPh)₂(dppm)] and [Pt(SeCb^oPh)₂(dppm)].     

Synthese und Struktur von [(Me2PhP)3Cl2ReN]2NbCl4 und [Re3N3Cl5(PMe2Ph)6][NbCl6]

Synthesis and Structure of [(Me₂PhP)₃Cl₂ReN]₂NbCl₄ and [Re₃N₃Cl₅(PMe₂Ph)₆][NbCl₆] The reaction of ReNCl₂(PMe₂Ph)₃ with NbCl₅ in toluene yields the trinuclear complexes [(Me₂PhP)₃Cl₂ReN]₂‐ NbCl₄ (1) and [Re₃N₃Cl₅(PMe₂Ph)₆][NbCl₆] ( 2 ). 1 forms triclinic crystals with the composition 1 · 2 C₇H₈ (P 1, a = 1074.5(1), b = 1289.1(2), c = 1299.3(2) pm, α = 85.25(2)°, β = 81.04(2)°, γ = 86.02(1)°, Z = 1). In the centrosymmetric compound 1 two complexes ReNCl₂(PMe₂Ph)₃ coordinate with their nitrido ligands a square planar, central unit NbCl₄ to form an almost linear arrangement Re≡N–Nb–N≡Re. The length of the Re–N triple bonds is 172,2 pm, and the Nb–N distances of 216.0 pm correspond to coordinative single bonds. 2 forms orthorhombic crystals with the space group P2₁2₁2₁ and a = 1286.0(1), b = 2109.2(4), c = 2436.2(3) pm, Z = 4. The three Re atoms are located at the corners of a triangle. They are connected by two asymmetric nitrido bridges and two asymmetric chloro bridges. The weakly bent nitrido bridges (Re–N–Re = 152° and 157°) are characterized by Re–N distances of 169 und 207 pm as well as 171 and 207 pm. Re1, in addition, binds a terminal nitrido ligand with Re1–N1 = 166 pm.     

Synthesis and spectroscopy of cis-configured mononuclear palladium(II) and platinum(II) complexes of chalcogeno o-carboranes and structures of [Pt(SCboPh)2(dppm)], [Pt(SeCboPh)2(dppm)], [Pt(SCboS)(PMe2Ph)2] and [Pt(SCboS)(PMePh2)2]

The reactions of [MCl₂(P^∩P)] and [MCl₂(PR₃)₂)] with 1-mercapto-2-phenyl-o-carborane/NaSeCb^oPh and 1,2-dimercapto-o-carborane yield mononuclear complexes of composition, [M(SCb^oPh)₂(P^∩P)], [M(SeCb^oPh)₂(P^∩P)] (M = Pd or Pt; P^∩P = dppm (bis(diphenylphosphino)methane), dppe (1,2-bis(diphenylphosphino)ethane) or dppp (1,3-bis(diphenylphosphino)propane)) and [M(SCb^oS)(PR₃)₂] (2PR₃ = dppm, dppe, 2PEt₃, 2PMe₂Ph, 2PMePh₂ or 2PPh₃). These complexes have been characterized by elemental analysis and NMR (¹H, ³¹P, ⁷⁷Se and ¹⁹⁵Pt) spectroscopy. The ¹J(Pt–P) values and ¹⁹⁵Pt NMR chemical shifts are influenced by the nature of phosphine as well as thiolate ligand. Molecular structures of [Pt(SCb^oPh)₂(dppm)], [Pt(SeCb^oPh)₂(dppm)], [Pt(SCb^oS)(PMe₂Ph)₂] and [Pt(SCb^oS)(PMePh₂)₂] have been established by single crystal X-ray structural analyses. The platinum atom in all these complexes acquires a distorted square planar configuration defined by two cis-bound phosphine ligands and two chalcogenolate groups. The carborane rings are mutually anti in [Pt(SCb^oPh)₂(dppm)] and [Pt(SeCb^oPh)₂(dppm)].     

Reactions of the Complexes ReNCl2(PMe2Ph)3, [ReNCl4]—, [OsO3N]—, and Cl3VNCl with Metal Halides

The nitrido complexes ReNCl₂(PMe₂Ph)₃ and [OsO₃N]^— have strong basic terminal nitrido ligands which can react with Lewis acidic metal halides to form nitrido bridges. The synthesis and structure of complexes with ReNCl₂(PMe₂Ph)₃ and nitrido bridges Re≡N‐M (M = B, Ga, Sn, Ti, Zr, V, Nb, Ta, Mo, Re, Pd, Au, and Zn) as well as of complexes with [OsO₃N]^— and nitrido bridges Os≡N‐M (M = Pd and Pt) are reported. Strong Lewis acids can also remove phosphine or chloro ligands from ReNCl₂(PMe₂Ph)₃. The resulting complex fragments subsequently combine to yield oligomeric complexes with nitrido bridges Re≡N‐Re. If the reaction with strong Lewis acids is carried out in a chlorinated solvent the solvent can be decomposed to form HCl which then protonates the nitrido ligand affording an imido complex. [ReNCl₄]^— is able to form nitrido bridges to electrophilic halides if a donor ligand is coordinated in trans position to the nitrido ligand to enhance its basicity sufficiently. The synthesis and structure of examples with nitrido bridges Re≡N‐M (M = Pd, Pt, Ta) are reported. The chloro imido complex Cl₃V≡N‐Cl can act as a nitride ion transfer reagent. Its reaction with MoCl₅ yields Mo₂NCl₈ whereas with MoCl₃ the nitride chlorides Mo₃N₂Cl₁₁ and MoNCl₃ are obtained. Cl₃VNCl can also act as an reactive intermediate by the reaction of VN with a halide as was shown by the reaction of MoCl₅ with VN yielding Mo₂NCl₇. The structures of these molybdenum nitride chlorides are discussed.     

Synthesis and Crystal Structures of the Novel Tetrameric Nitrido Complexes [{cyclo-ReN}4(S2CNEt2)6(MeOH)2(PPh3)2][BPh4]2 · CH2Cl2 · 2 H2O and [{cyclo-ReN}4(S2CNEt2)4Cl4(PMe2Ph)4] · 2 acetone

Novel tetrameric rhenium(V) complexes have been prepared from [ReNCl₂(PPh₃)₂] and [ReN(PMe₂Ph)(S₂CNEt)₂], respectively. [ReNCl₂(PPh₃)₂] reacts with 1.5 equivalents of KS₂CNEt₂ in methanol to yield the unusual dark red species [{cyclo-ReN}₄(S₂CNEt₂)₆(MeOH)₂(PPh₃)₂][BPh₄]₂ · CH₂Cl₂ · 2 H₂O ( 1 ). The crystal structure of the tetramer (triclinic, space group P1, a = 13.842(2), b = 15.213(2), c = 16.796(3) Å, α = 67.88(1), β = 70.90(1), γ = 88.05(1)°, U = 3080.2(8) ų, Z = 1) shows four rhenium atoms in a square configuration which are bridged via linear asymmetric Re≡N–Re groups with bond lengths of about 169 and 203 pm. The molecule contains a centre of symmetry with two distinct octahedral rhenium environments. The first rhenium environment contains two bidentate dithiocarbamate ligands which complete the octahedral geometry and the second contains a bidentate dithiocarbamate ligand, coordinated methanol and has retained a single phosphine coligand. A symmetric compound containing the {cyclo-ReN}₄ core is obtained from the reaction of [ReN(PMe₂Ph)(S₂CNEt₂)₂] with Al₂Cl₆ in acetone. [{cyclo-ReN}₄(S₂CNEt₂)₄Cl₄(PMe₂Ph)₄] · 2 acetone ( 2 ) forms red crystals (monoclinic, space group C2/c, a = 21.432(6), b = 13.700(3), c = 28.060(9) Å, β = 102.37(1)°, U = 8048(4) Å3, Z = 4) with each rhenium atom coordinated by a bidentate dithiocarbamato, a phosphine and a chloro ligand. The non-planar 8-membered {ReN}₄ ring contains asymmetric Re≡N–Re bridges (mean values: 1.69 Å and 2.029 Å, respectively). In contrast, reaction of [ReNCl(S₂CNEt₂)(PMe₂Ph)₂] with one equivalent of K[S₂CN(Me)CH₂CH₂NMe₃]I gave the mixed dithiocarbamato-cation [ReN(S₂CNEt₂)(S₂CN(Me)CH₂CH₂NMe₃)(PMe₂Ph)]⁺ ( 3 ) which was isolated as a tetraphenylborate salt.     

Unusual Structure,Fluxionality, and Reaction Mechanism of Carbonyl Hydrosilylation by Silyl Hydride Complex [(ArN)Mo(H)(SiH2Ph)(PMe3)3]

The reactions of bis(borohydride) complexes [(RN?)Mo(BH₄)₂(PMe₃)₂] ( 4 : R=2,6‐Me₂C₆H₃; 5 : R=2,6‐iPr₂C₆H₃) with hydrosilanes afford new silyl hydride derivatives [(RN?)Mo(H)(SiR′₃)(PMe₃)₃] ( 3 : R=Ar, R′₃=H₂Ph; 8 : R=Ar′, R′₃=H₂Ph; 9 : R=Ar, R′₃=(OEt)₃; 10 : R=Ar, R′₃=HMePh). These compounds can also be conveniently prepared by reacting [(RN?)Mo(H)(Cl)(PMe₃)₃] with one equivalent of LiBH₄ in the presence of a silane. Complex 3 undergoes intramolecular and intermolecular phosphine exchange, as well as exchange between the silyl ligand and the free silane. Kinetic and DFT studies show that the intermolecular phosphine exchange occurs through the predissociation of a PMe₃ group, which, surprisingly, is facilitated by the silane. The intramolecular exchange proceeds through a new non‐Bailar‐twist pathway. The silyl/silane exchange proceeds through an unusual Mo^VI intermediate, [(ArN?)Mo(H)₂(SiH₂Ph)₂(PMe₃)₂] ( 19 ). Complex 3 was found to be the catalyst of a variety of hydrosilylation reactions of carbonyl compounds (aldehydes and ketones) and nitriles, as well as of silane alcoholysis. Stoichiometric mechanistic studies of the hydrosilylation of acetone, supported by DFT calculations, suggest the operation of an unexpected mechanism, in that the silyl ligand of compound 3 plays an unusual role as a spectator ligand. The addition of acetone to compound 3 leads to the formation of [trans‐(ArN)Mo(OiPr)(SiH₂Ph)(PMe₃)₂] ( 18 ). This latter species does not undergo the elimination of a Si? O group (which corresponds to the conventional Ojima′s mechanism of hydrosilylation). Rather, complex 18 undergoes unusual reversible β‐CH activation of the isopropoxy ligand. In the hydrosilylation of benzaldehyde, the reaction proceeds through the formation of a new intermediate bis(benzaldehyde) adduct, [(ArN?)Mo(η²‐PhC(O)H)₂(PMe₃)], which reacts further with hydrosilane through a η¹‐silane complex, as studied by DFT calculations.