cis‐Tetracarbonylbis(tricyclohexyl­phosphine)molybdenum(0) and pentacarbonyl(tricyclohexylphos­phine)molybdenum(0)

In the present redetermination of the complex cis‐tetra­carbonyl­bis­(tri­cyclo­hexyl­phosphine)molybdenum(0), (I), [Mo(C₁₈H₃₃P)₂(CO)₄] or cis‐{η¹‐[P(C₆H₁₁)₃]₂}Mo(CO)₄, the Mo atom has a distorted octahedral geometry with a large P—Mo—P angle of 104.8 (1)°. A strong trans influence on the carbonyls in (I) is seen in a shortening of the Mo—C and a lengthening of the C—O distances opposite the phosphines compared with those that are cis. This influence is greatly diminished in the complex penta­carbonyl­(tri­cyclo­hexyl­phosphine)­molyb­denum(0), (II), [Mo(C₁₈H₃₃P)(CO)₅] or {η¹‐[P(C₆H₁₁)₃]}­Mo(CO)₅, the core of which has a slightly distorted C_4v geometry.     

Bonding Analysis of N‐Heterocyclic Carbene Tautomers and Phosphine Ligands in Transition‐Metal Complexes: A Theoretical Study

DFT calculations at the BP86/TZ2P level were carried out to analyze quantitatively the metal–ligand bonding in transition‐metal complexes that contain imidazole (IMID), imidazol‐2‐ylidene (nNHC), or imidazol‐4‐ylidene (aNHC). The calculated complexes are [Cl₄TM(L)] (TM=Ti, Zr, Hf), [(CO)₅TM(L)] (TM=Cr, Mo, W), [(CO)₄TM(L)] (TM=Fe, Ru, Os), and [ClTM(L)] (TM=Cu, Ag, Au). The relative energies of the free ligands increase in the order IMID<nNHC<aNHC. The energy levels of the carbon σ lone‐pair orbitals suggest the trend aNHC>nNHC>IMID for the donor strength, which is in agreement with the progression of the metal–ligand bond‐dissociation energy (BDE) for the three ligands for all metals of Groups 4, 6, 8, and 10. The electrostatic attraction can also be decisive in determining trends in ligand–metal bond strength. The comparison of the results of energy decomposition analysis for the Group 6 complexes [(CO)₅TM(L)] (L=nNHC, aNHC, IMID) with phosphine complexes (L=PMe₃ and PCl₃) shows that the phosphine ligands are weaker σ donors and better π acceptors than the NHC tautomers nNHC, aNHC, and IMID.     

Kinetics and mechanism of ligand substitution reactions in [cis-M(CO)4(amine)(EPh3)] complexes (M = Mo,W; amine = pyridine,piperidine; E = As,Sb)

Group 6 metal carbonyls [cis-M(CO)₄(amine)(EPh₃)] (M = Mo, W; amine = piperidine (pip), pyridine (py); E = As, Sb) have been prepared and characterized. These complexes react thermally in chlorobenzene solutions with phosphine or phosphite ligands (= L) to give cis- and trans-M(CO)₄(L)(EPh₃) products. Kinetics of amine substitution by L in these complexes, under pseudo-first-order conditions, indicate that these reactions proceed by a rate law that is first-order in concentration of the metal complex. Rate constants and activation parameters for these reactions have been determined and are discussed. Competition studies for the [M(CO)₄(EPh₃)] intermediates show that these intermediates are highly reactive and react almost indiscriminately with various incoming nucleophiles with slight preference for more basic ones.     

Synthesis and X-ray structural characterization of mono(aminophosphine) derivatives of molybdenum hexacarbonyl, Mo(CO)5L {L?=?P(NC5H10)3, P(Ph)(NC4H8O)2 or P(Ph){N(i-C3H7)2}(NC4H8O)}

Equimolar reactions of molybdenum hexacarbonyl with tris(piperidino)phosphine (L1), bis(morpholino)(phenyl)phosphine (L2), and (Di-isopropylamino)(morpholino)(phenyl) phosphine (L3), which are examples of symmetrically and unsymmetrically substituted tertiary(amino)phosphines, afford the corresponding mono derivatives, Mo[P(NC₅H₁₀)₃)](CO)₅ (1), Mo[P(Ph)(NC₄H₈O)₂](CO)₅ (2), and Mo[P(Ph){N(i-C₃H₇)₂}(NC₄H₈O)](CO)₅ (3) in moderate yields as air stable crystalline solids. In the case of L1, some amount of trans-bis derivative, Mo[P(NC₅H₁₀)₃)]₂(CO)₄ (4), was also isolated. X-ray structures of 1, 2, and 3 have been determined. Compounds 1 and 2 crystallize in the monoclinic system with space group P21/c, while 3 crystallizes in the triclinic system with space group Pī. While the Mo-P and Mo-C_ax bond distances in these complexes are comparable with those of other P-C bonded phosphines, the presence of chiral phosphine seems to induce a relatively weaker interaction with the molybdenum center. Intermolecular hydrogen bonding is seen in compound 1.     

Pseudohalogenogermylenes versus Halogenogermylenes: Difference in their Complexation Behavior towards Group 6 Metal Carbonyls

Pseudohalogenogermylenes [(iBu)₂ATI]GeY (Y=NCO 4 , NCS 5 ) show different coordination behavior towards group 6 metal carbonyls in comparison to the corresponding halogenogermylenes [(iBu)₂ATI]GeX (X=F 1 , Cl 2 , Br 3 ) (ATI=aminotroponiminate). The reactions of compounds 4 – 5 and 1 – 3 with cis‐[M(CO)₄(COD)] (M=Mo, W, COD=cyclooctadiene) gave trans‐germylene metal complexes {[(iBu)₂ATI]GeY}₂M(CO)₄ (Y=NCO, M=Mo 6 , W 11 ; Y=NCS, M=Mo 7 ) and cis‐germylene metal complexes {[(iBu)₂ATI]GeX}₂M(CO)₄ (M=Mo, X=F 8 , Cl 9 , Br 10 ; M=W, X=Cl 12 ), respectively. Theoretical studies on compounds 7 and 9 reveal that donor–acceptor interactions from Mo to Ge atoms are better stabilized in the observed trans and cis geometries than in the hypothetical cis and trans structures, respectively.     

Determination of the Tolman cone angle from crystallographic parameters and a statistical analysis using the crystallographic data base

Summary A new method of evaluating the Tolman cone angle from X-ray structural data available from the Cambridge Crystallographic Data Base has been developed and a statistical analysis of the cone angles of the phosphines PPh₃, PMe₂Ph, PMePh₂, PMe₃, PEt₃ and PCy₃ (Cy = cyclohexyl) in transition metal complexes has been completed.     

Studies of chelation : II. Phosphine complexes of molybdenum and manganese

Activation parameters have been obtained for the chelation of Mo(CO)₅dpe (dpe = Ph₂PCH₂CH₂PPh₂) and of Mo(CO)₅dmpe (dmpe = Me₂PCH₂CH₂PMe₂) to give cis-Mo(CO)₄dpe and cis-Mo(CO)₄dmpe respectively. The results are compared with those for the analogous chromium complexes and show that the enthalpy contribution determines the more rapid chelation in the molybdenum complexes. The preparation and properties of the chelate-bridged hetero-metallic complex (CO)₅ModmpeMn(CO)₄Br are reported. The reaction between Et₄N[Mn(CO)₄X₂] (X = Cl, Br) and bidentate ligands dpe, dmpe and ape (ape = Ph₂PCH₂CH₂AsPh₂) in the presence of either silver(I) tetrafluoroborate or Et₃OBF₄ produces cis-Mn(CO)₄X(bidentate) which is identified by infrared and mass spectrometry. At room temperature the Mn(CO)₄X(bidentate) complex is rapidly converted to the chelated fac-Mn(CO)₃X(bidentate) complex. The chelation process is approximately 10⁴ times more rapid than in the isoelectronic chromium(O) complexes. The preparation and characterisation of fac-Mn(CO)₃Br(dmpe), cis-Mn(CO)₄Br(PMe₃) and fac-Mn(CO)₃Br(PMe₃)₂ are reported.     

Template‐Controlled Assembly of Ditopic Catechol Phosphines: A Strategy for the Generation of Complexes of Bidentate Phosphines with Different Bite Angles

A rational approach to the synthesis of heterobi‐ or ‐trimetallic complexes based upon self‐assembly of a flexible ditopic catechol‐phosphine ligand with [(cod)PdCl₂] and simple metal halides such as GaCl₃, BiCl₃, SnCl₄, or ZrCl₄ is described. All products were characterized by spectroscopic and analytical data and single‐crystal X‐ray diffraction studies. The molecular structures can be described in terms of cis‐configured palladium complexes with supramolecular bisphosphine ligands that are formed by the assembly of two phosphine catecholate fragments on a main group/transition metal template. Of particular interest are the distinct decreases in P‐Pd‐P bite angles and P???P distances between the ligating atoms with increasing covalent radii of the templates. The range of these variations is of a magnitude similar to that of the geometrical changes in known families of complexes containing molecular bidentate ligands. Solution NMR studies give further evidence that in several cases the μ₂‐bridging coordination of two of the catechol oxygen atoms in the template complexes is broken under the influence of donor solvents, thus allowing the supramolecular ligand to be switched between tetradentate ‐O₂P₂ and bidentate ‐P₂ coordination modes.     

Reactions and spectroscopic studies of Group 6 metal carbonyls with pyrazinecarboxamide and certain phosphine ligands

Substitution reactions of phosphine ligands, triphenylphosphine (PPh₃), tri(m-chlorophenyl)phosphine (m-ClPPh₃), tri(p-methoxyphenyl)phosphine (p-MeOPPh₃) and tri(benzyl)phosphine (PBz₃) with [M(CO)₄(PCA)] (M?=?Cr, Mo and W, PCA?=?pyrazinecarboxamide) were found to be dependent on the type of metal and phosphine ligand. The complexes were characterized by elemental analysis, mass spectrometry, and IR and ¹H NMR spectroscopy. UV–vis spectra of the complexes in different solvents showed bands due to metal-to-ligand charge transfer.     

杂双核(H)Rh-Cr配合物中乙烯插入RhI—H键反应的密度泛函研究

采用密度泛函理论B3LYP方法研究了配体和配位数对乙烯插入杂双核(CO)₄Cr(m-PH₂)₂RhH(L_n) (L＝CO或PH₃, n＝1或2)配合物中Rh—H键反应的影响. 计算结果表明, 六配位乙烯复合物中乙烯与铑之间轨道相互作用主要为乙烯到铑中心的s供体相互作用; 而五配位乙烯复合物中乙烯与铑中心间相互作用涉及乙烯到铑中心的s供体相互作用和铑到乙烯的p反馈作用. PH₃配体在热力学上不利于该反应. 处于氢配体对位的膦配体能加速乙烯插入反应. 乙烯插入的五配位反应途径占优势. Cr(CO)₄部分的引入降低了乙烯插入反应的活化能.     

Transition Metal Chemistry of Main Group Hydrazides. 17. Triphosphine derived from phosphanyl hydrazide as a building block for hetero trimetallic compounds. Synthesis and coordination chemistry of ((Me2P)2N?N(Me)(PMe2))

The new triphosphine (Me₂P)₂N? N(Me)(PMe₂) ( 1 ), has been synthesized in pure form by the reaction of methylhydrazine with dimethylchlorophosphine in the presence of triethylamine. This triphosphine represents a bridge between phosphinoamine (>P? N(R)? P<) and phosphanyl hydrazide (>P? N(R)? N(R)? P<) backbones. Reaction of 1 with cis-[W(CO)₄(NHC₅H₁₀)₂] proceeds via two coordination modes to give four-membered M? P? N? P and five-membered M? P? N? N? P metallacyclic frameworks. The tungsten complex cis-[W(CO)₄{(Me₂P)₂NN(Me)(PMe₂)}] ( 2 ) possessing an uncoordinated phosphine moiety to prepare multimetallic organometallic compounds. For example, reactions of 2 with PdCl₂(PhCN)₂ and PtCl₂(COD) produced the trimetallic complexes consisting of W(0)? Pt(II) and W(0)? Pd(II) centers respectively in good yields. The different isomers of these trinuclear complexes have been clearly identified by ³¹P NMR spectroscopy.     

Polynuclear metal complexes incorporating hydrido-phosphido ligands

Addition of phosphines to the coordinatively unsaturated species (Cp)₂M₂(CO)₄ (M = Mo, W) and H₂Os₃(CO)₁₀ yield a series of products incorporating terminal phosphine along with bridging and capping phosphido ligands formed via insertion into PH bonds. The complexes were characterised by ¹H and ³¹P NMR spectroscopy and mass spectrometry.     

Darstellung und spektroskopische Untersuchungen von M(CO)4L2- und M(CO)3L3-Komplexen (M = Cr,Mo, W; L = Me3SiOCH2PMe2, Me2(CH2CH) SiOCH2PMe2)

Preparation and spectroscopical Investigations of M(CO)₄L₂ and M(CO)₃L₃ Complexes (M = Cr, Mo, W; L = Me₃SiOCH₂PMe₂, Me₂(CH₂?CH)SiOCH₂PMe₂ The coordinating properties of the ligands L¹ (?Me₃SiOCH₂PMe₂) and L² (?Me₂ViSiOCH₂PMe₂)¹) have been studied by synthesis and spectroscopic investigations (IR, NMR, MS) of their complexes M(CO)₄L₂ and M(CO)₃L₃(M = Cr, Mo, W). The complexes are obtained by replacement of norbornadiene (NBD) in M(CO)₄NBD or cycloheptatriene CHT in M(CO)₃CHT. Spectroscopic data (v(CO), δ δ) support the σ-donor/-π-acceptor model of the MP bonds.     

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).     

B,B, B-Trimethyl-N,N, N-triäthylborazin- und B,B, B-Triäthyl-N,N, N-trimethylborazin-molybdäntricarbonyl

The title compounds have been prepared in low yields starting with cis-(CH₃CN)₃-Mo(CO)₃ or Mo(CO)₆ (photochemical route). The new complexes are generally less stable than the corresponding hexaalkylborazine-chromium compounds and react very smoothly with Lewis bases by cleavage of the borazine-metal bond. The IR.-spectra indicate the similarity of type of bonding in hexaalkylborazine-molybdenum and -chromium complexes.     

The use of half-sandwich iridium dithiolate and diselenolate complexes, Cp*Ir(L)(ER)2 (L=CO, PMe3, PPh3; ER=SPh, SePh, SeMe), for the synthesis of heterodimetallic compounds. The molecular structure of Cp*Ir(CO)(μ-SePh)2[Mo(CO)4]

Carbonyl–iridium half-sandwich compounds, Cp*Ir(CO)(EPh)₂ (E=S, Se), were prepared by the photo-induced reaction of Cp*Ir(CO)₂ with the diphenyl dichalcogenides, E₂Ph₂, and used as neutral chelating ligands in carbonylmetal complexes such as Cp*Ir(CO)(μ-EPh)₂[Cr(CO)₄], Cp*Ir(CO)(μ-EPh)₂[Mo(CO)₄] and Cp*Ir(CO)(μ-EPh)₂[Fe(CO)₃], respectively. A trimethylphosphane–iridium analogue, Cp*Ir(PMe₃)(μ-SeMe)₂[Cr(CO)₄], was also obtained. The new heterodimetallic complexes were characterized by IR and NMR spectroscopy, and the molecular geometry of Cp*Ir(CO)(μ-SePh)₂[Mo(CO)₄] has been determined by a single crystal X-ray structure analysis. According to the long Ir…Mo distance (395.3(1) Å), direct metal–metal interactions appear to be absent.     

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).     

Photochemistry of (Me3P)4Mo(η-CO2)2: Deoxygenation of coordinated carbon dioxide and phosphine oxidation

Irradiation of the title compound 1 through quartz in toluene solution at − 20°C produces cis-Mo(CO)₂(PMe₃)₄ and OPMe₃ as the major products along with lesser amounts of mer- and _fac-Mo(CO)₃(PMe₃)₃ and Mo(CO)PMe₃) ₅. Irradiation of 1 through Pyrex produces in addition substantial amounts of an unstable species formulated as trans-Mo (CO)₂(PMe₃)₄.     

Substituierte halogencarbonylmetallate des chroms,Molybdäns und Wolframs : II. Photochemische phosphin-abspaltung,ein neuer weg zu metall (VI A) carbonylderivaten

Irradiation of bis(phosphine) tetracarbonyl complexes L₂M(CO)₄ (M = Cr, Mo, W) in the presence of donor ligands (amine, nitrile, halide ion) leads, via loss of one phosphine ligand, to neutral (LL′M(CO)₄) or ionic ([LM(CO)₄X]^?) metal carbonyl compounds. The use of this reaction as the first step in a general synthesis of unsymmetrically disubstituted derivatives of Group VIA hexacarbonyls is discussed.     

Rhenium–Germanium Triple Bonds: Syntheses and Reactions of the Germylidyne Complexes mer‐[X2(PMe3)3ReGe?R] (X=Cl,I, H; R=m‐terphenyl)

A general approach to the first compounds that contain rhenium–germanium triple and double bonds is reported. Heating [ReCl(PMe₃)₅] ( 1 ) with the arylgermanium(II) chloride GeCl(C₆H₃‐2,6‐Trip₂) ( 2 ; Trip=2,4,6‐triisopropylphenyl) results in the germylidyne complex mer‐[Cl₂(PMe₃)₃Re?Ge? C₆H₃‐2,6‐Trip₂] ( 4 ) upon PMe₃ elimination. An equilibrium that is dependent on the PMe₃ concentration exists between complexes 1 and 4 . Removal of the volatile PMe₃ shifts the equilibrium towards complex 4 , whereas treatment of 4 with an excess of PMe₃ gives a 1:1 mixture of 1 and the PMe₃ adduct of 2 , GeCl(C₆H₃‐2,6‐Trip₂)(PMe₃) ( 2 ‐PMe₃). Adduct 2 ‐PMe₃ can be selectively obtained by addition of PMe₃ to chlorogermylidene 2 . The NMR spectroscopic data for 2 ‐PMe₃ indicate an equilibrium between 2 ‐PMe₃ and its dissociation products, 2 and PMe₃, which is shifted far towards the adduct site at ambient temperature. NMR spectroscopic monitoring of the reaction of complex 1 with 2 and the reaction of complex 4 with PMe₃ revealed the formation of two key intermediates, which were identified to be the chlorogermylidene complexes cis/trans‐[Cl(PMe₃)₄Re?Ge(Cl)C₆H₃‐2,6‐Trip₂] (cis/trans‐ 3 ) by using NMR spectroscopy. Labile chlorogermylidene complexes cis/trans‐ 3 can be also generated from trans‐[Cl(PMe₃)₄Re?Ge? C₆H₃‐2,6‐Trip₂]BPh₄ ( 9 ) and (nBu₄N)Cl at low temperature, and decompose at ambient temperature to give a mixture of complexes 1 and 4 . Complex 4 reacts with LiI to give the diiodido derivative mer‐[I₂(PMe₃)₃Re?Ge? C₆H₃‐2,6‐Trip₂] ( 5 ), which undergoes a metathetical iodide/hydride exchange with Na(BEt₃H) to give the dihydrido germylidyne complex mer‐[H₂(PMe₃)₃Re?Ge? C₆H₃‐2,6‐Trip₂] ( 6 ). Carbonylation of 4 induces a chloride migration from rhenium to the germanium atom to afford the chlorogermylidene complex mer‐[Cl(CO)(PMe₃)₃Re?Ge(Cl)C₆H₃‐2,6‐Trip₂] ( 7 ). Similarly, MeNC converts complex 4 into the methylisocyanide analogue mer‐[Cl(MeNC)(PMe₃)₃Re?Ge(Cl)C₆H₃‐2,6‐Trip₂] ( 8 ). Chloride abstraction from 4 by NaBPh₄ in the presence of PMe₃ gives the cationic germylidyne complex trans‐[Cl(PMe₃)₄Re?Ge? C₆H₃‐2,6‐Trip₂]BPh₄ ( 9 ). Heating complex 4 with cis‐[Mo(PMe₃)₄(N₂)₂] induces a germylidyne ligand transfer from rhenium to molybdenum to afford the germylidyne complex trans‐[Cl(PMe₃)₄Mo?Ge? C₆H₃‐2,6‐Trip₂] ( 10 ). All new compounds were fully characterized and their molecular structures studied by X‐ray crystallography, which led to the first experimentally determined Re? Ge triple‐ and double‐bond lengths.