Synthesis and characterization of deuterium-labelled (fulvene)M(CO)3 complexes (M = Cr, Mo)

The preparation and characterization of a series of deuterium-labelled (fulvene)M(CO)₃ (M = Cr, Mo) complexes is reported. (η⁵-6-Dimethylaminofulvene-d₂)Cr(CO)₃ and (η⁵-6-dimethylaminofulvene-d₂)Mo(CO)₃ were obtained in high yields by reacting the deuterated fulvene ligands with (MeCN)₃M(CO)₃ (M = Cr, Mo). In addition, syntheses of 6,6-diphenylfulvene-d₁₀ and 6,6-diphenyl-1,2-benzofulvene-d₁₀ as well as the corresponding tricarbonylchromium complexes are described.     

Synthesis and reactivity of cationic bipyridine tungsten(0) and molybdenum(0) nitrosyl complexes

A variety of Group 6 mono bipyridine (bpy) complexes were prepared, and substitution reactions of [(bpy)(MeIm)M(CO)₂(NO)]PF₆ complexes (MeIm = 1-methylimidazole, M = W or Mo) were investigated. Nitrosylation of complexes having the general formula (bpy)(L)M(CO)₃ (L = a variable ligand) gave cationic complexes of the form [(bpy)(L)M(CO)₂(NO)]PF₆. The structure of [(bpy)(MeIm)W(CO)₂(NO)]PF₆ was confirmed by single-crystal X-ray diffractometry. [(bpy)(MeIm)M(CO)₂(NO)]PF₆ complexes undergo facile substitutions with mono-, tri- and tetra-dentate ligands, yielding di- or mono-carbonyl mononitrosyl complexes. The structures of [(bpy)(PMe₃)₂W(CO)(NO)]PF₆ and [(dien)(PMe₃)W(CO)(NO)]PF₆ (dien = diethylenetriamine) were determined by X-ray diffraction.     

Synthesis and characterization of Cr,Mo and W carbonyl complexes of bis(2-(diphenylphosphino)ethyl)benzylamine

Various Cr, Mo and W carbonyl complexes of a tridentate ligand containing N and P as donor atoms, bis(2-(diphenylphosphino)ethyl)benzylamine (DPBA), have been synthesized. Reaction of M(CO)₆ (M = Cr, Mo and W) with DPBA in a 1:1 mole ratio in toluene or xylene, resulted in the formation of facial and meridional complexes of the type [M(CO)₃(DPBA)] (M = Cr, Mo and W). Interaction of Cr(CO)₆ or Mo(CO)₆ with DPBA and PPh₃ in toluene yielded complexes of the composition [Cr(CO)₃(DPBA)(PPh₃)] and [Mo(CO)₂(DPBA)(PPh₃)], respectively. However reaction of W(CO)₆ with DPBA and PPh₃ yielded only [W(CO)₃(DPBA)]. Reaction of Cr(CO)₆ with DPBA and 1,2-bis(diphenylphosphino)ethane(diphos) in toluene for 24 h resulted in the formation of a mixed ligand complex, [Cr(CO)₄(DPBA)(diphos)] where both the ligands coordinate to the metal atom through only one of their donor atoms. A unique binuclear complex of the composition [Mo(CO)₂(DPBA)(diphos)]₂ resulted, with the tridentate ligand DPBA acting as a bidentate bridging ligand, by the reaction of Mo(CO)₆ with DPBA and diphos in refluxing xylene for 24 h. All the complexes are characterized by elemental analysis and infrared spectra. The ³¹P{¹H} and ¹H NMR spectral data of the complexes gave valuable information in elucidating the structures of the complexes. The ligand DPBA has found to behave in a triligate monometallic, biligate monometallic, monoligate monometallic and biligate bimetallic manner.     

Heptacoordinate dithiophosphate W(II) and Mo(II) complexes of diphosphines and iodide

New complexes [MI(CO)₂(dppe){S₂P(OEt)₂}] (M=W, 1a; M=Mo, 1b), [MI(CO)₂(dppm){S₂P(OEt)₂}] (M=W, 2a; M=Mo, 2b) and [W(CO)(dppe){S₂P(OEt)₂}₂][O₂dppe] (3a), were synthesised from [MI₂(CO)₃(NCMe)₂] (M=Mo, W), after treatment with ammonium diethyldithiophosphate and phosphine under different conditions. The structure of the tungsten complexes was determined by single crystal X-ray diffraction. During the synthesis of 3a, oxidation of the phosphine took place and a molecule of oxidised phosphine occupies channels in the crystal. DFT/B3LYP calculations on models of 1a and 2a showed the capped octahedron structure, observed in most dicarbonyl complexes of this family, to be preferred by 1.4 and 2.6 kcal mol⁻¹ for the dppm and the dppe complexes, respectively. Strong steric repulsions can reverse this trend, as happens with the rigid dppm ligand. Complex 1a adopts a pentagonal bipyramidal geometry, which is often found in related monocarbonyl complexes.     

Photochemical reactions of bis(bistrimethylsilylamido)tin(II) with; Hexacarbonylmolybdenum and tungsten

Irradiation of M(CO)₆ (M = Mo. W) and Sn[N(SiMe₃)₂]₂ in hexane with UV light results in carbonyl substitution to form both M(CO)₅Sn[N(SiMe₃)₂]₂ and M(CO)₄Sn[N(SiMe₃)₂]₂)₂ complexes. The M(CO)₄L₂ species present the first examples in which both cis and trans isomers have been observed upon substitution of bulky divalent main group IV ligands. The highly air-sensitive W(CO)₅L and W(CO)₄L₂ complexes have been isolated.     

Electrochemical oxidation of Mo(CO)4(LL) and Mo(CO)3(LL)(CH3CN): Generation, infrared characterization, and reactivity of [Mo(CO)4(LL)] and [Mo(CO)3(LL)(CH3CN)] (LL = 2,2′-bipyridine, 1,10-phenanthroline and related ligands)

Mo(CO)₄(LL) complexes, where LL = polypyridyl ligands such as 2,2′-bipyridine and 1,10-phenanthroline, undergo quasi-reversible, one-electron oxidations in methylene chloride yielding the corresponding radical cations, [Mo(CO)₄(LL)]⁺. These electrogenerated species undergo rapid ligand substitution in the presence of acetonitrile, yielding [Mo(CO)₃(LL)(CH₃CN)]⁺; rate constants for these substitutions were measured using chronocoulometry and were found to be influenced by the steric and electronic properties of the polypyridyl ligands. [Mo(CO)₃(LL)(CH₃CN)]⁺ radical cations, which could also be generated by reversible oxidation of Mo(CO)₃(LL)(CH₃CN) in acetonitrile, can be irreversibly oxidized yielding [Mo(CO)₃(LL)(CH₃CN)₂]²⁺ after coordination by an additional acetonitrile. Infrared spectroelectrochemical experiments indicate the radical cations undergo ligand-induced net disproportionations that follow first-order kinetics in acetonitrile, ultimately yielding the corresponding Mo(CO)₄(LL) and [Mo(CO)₂(LL)(CH₃CN)₃]²⁺ species. Rate constants for the net disproportionation of [Mo(CO)₃(LL)(CH₃CN)]⁺ and the carbonyl substitution reaction of [Mo(CO)₃(LL)(CH₃CN)₂]²⁺ were measured. Thin-layer bulk oxidation studies also provided infrared characterization data of [Mo(CO)₄(ncp)]⁺ (ncp = neocuproine), [Mo(CO)₃(LL)(CH₃CN)]⁺, [Mo(CO)₃(LL)(CH₃CN)₂]²⁺ and [Mo(CO)₂(LL)(CH₃CN)₃]²⁺ complexes.     

Preparation and structure of bis(trifluoroacetato)dicarbonyl bis(triethylphosphine)molybdenum(lI)

The Mo(CO)₂(PEt₃)₂(CF₃COO)₂ complex, obtained by prolonged reaction of trifluoroacetic acid with Mo(CO)₃(PEt₃₎₃ in dichloromethane, was characterized by spectroscopic methods and by X-ray crystal structure determination. The crystals belong to the monoclinic space group Cc, with a = 20.037, b = 10.879, _c = 15.176 Å,β/3 = 129.28° and _Z = 4. The structure was refined on 2135 observed reflections to R = 0.047. The Mo(II) atom is 7-coordinated and has a capped trigonal prism geometry, the capping position being occupied by a monodentate CF₃CO₂ ligand. The quadrangular plane contains one CO, one PEt₃ and one bidentate CF₃CO₂ ligand. The remaining CO and PEt₃ molecules are found on the opposite edge.     

Synthesis and spectroscopic properties of some new seven-coordinate thioacetamide complexes of molybdenum(II) and tungsten(II)

The compounds [MI₂(CO)₃(NCMe)₂] (M = Mo or W) react with one equivalent of SC(NH₂)Me in CH₂Cl₂ at room temperature to initially give the acetonitrile substituted products [MI₂(CO)₃(NCMe)- {SC(NH₂)Me}] which was isolated for M = W. However, the molybdenum complex rapidly dimerizes with loss of acetonitrile to give the iodide-bridged compound [Mo(σ-I)I(CO)₃ {SC(NH₂)Me}]₂. The tungsten complex does not appear to dimerize, even after stirring at room temperature for 72 h in CH₂Cl₂. Two equivalents of thioacetamide react with [MI₂- (CO)₃(NCMe)₂] in CH₂Cl₂ at room temperature to give the new bisthioacetamide compounds [MI₂- (CO)₃{SC(NH₂)Me}₂] via displacement of the labile acetonitrile ligands. The low temperature (−70 °C) ¹³C NMR spectrum of [WI₂(CO)₃{SC(NH₂)Me}₂] indicates that the geometry of the complex is capped octahedral with a carbonyl ligand in the unique capping position.     

Synthesis,structure, reactivity and electrochemistry of a new molybdenum(0) dithiocarbamato complex, [Et4N][Mo(CO)4(S2CNEt2)]

A new molybdenum(0) dithiocarbamato complex [Et₄N] [Mo(CO)₄(S₂CNEt₂)] (1) has been synthesized by the reaction of Mo(CO)₆, NaS₂CNEt₂ and Et₄NCl in MeCN and characterized by routine elemental analysis, spectroscopy methods. The crystal and molecular structure of 1 was determined from X-ray three dimension data. 1 crystallizes in the orthorhombic, space group Pbc2₁ with a= 8.148(2), b=19.618(2), c=14.354(2) Å; V=2294 ų; Z=4; R₁=0.052, R₂=0.058 for 1308 independent reflections with I ⩾ 3σ(I). The geometry around Mo(0) atom in the anion [Mo(CO)₄(S₂CNEt₂)]^- of 1 is distorted octahedral with a small SMoS of 67.70° and a small angle of 3.6° between plane MoSS and MoC(1)C(2). Two groups of MoCO bond distances and the longer MoS bond distance observed in 1 are similar to that in the dinuclear Mo(0) complexes containing SR bridges but very different from those observed in the dithiocarbamato complexes of Mo in higher oxidation states. Different oxidizing products containing Mo in II-V oxidation states Mo(CO)₂(S₂CNEt₂)₂, MoO(S₂CNEt₂)₂, Mo₂O₃(S₂CNEt₂)₄ and Mo₂O₄(S₂CNEt₂)₂ were isolated from the oxidation of 1 with I₂ (or in the presence of traces of air). The electrochemical behavior of 1 in MeCN was investigated by cyclic voltammetry at Pt and C electrodes. The anodic peaks observed at 0.04, 0.14, 0.26 and 0.44 V versus SCE implied that 1 probably underwent oxidation in company with dissociation of dithiocarbamate and substitution of carbonyls resulting in several complexes of Mo in different oxidation states. The relationship between reactivity and structure is also discussed.     

Reinvestigation of the visible absorption bands of the 2,2′-bipyrimidine complexes W(CO)4(bpym) and (μ-bpym)[M(CO)4]2 (M=Mo, W) with resonance Raman spectroscopy; the emission spectrum of (μ-bpym)[Mo(CO)4]2

The character of the two lowest energy transitions of W(CO)₄(bpym) and (μ-bpym)[M(CO)₄]₂ (M=Mo, W) were established with resonance Raman spectroscopy. According to these spectra the two bands belong to MLCT transitions to different π* orbitals of the bpym ligand. Contrary to expectations it is not the first (lowest energy) but the second and more intense electronic transition which, according to the resonance Raman spectra, is directed to the lowest lying π* orbital (b_2u*, LUMO) of these complexes. This interpretation explains the different band intensities and the untypically low g values of the ESR signals of corresponding anion radicals. Excitation of (μ-bpym)[Mo(CO)₄]₂ in CH₂Cl₂ at 400 nm produced a weak emission with an onset at 700 nm. According to the excitation spectrum, this emission originates from the lowest MLCT-excited state of the complex.     

Solid state structure and reactivity in solution. 8. Implications of the structure of [1,2-bis(diphenylphosphino)ethane] tetra-carbonylmolybdenum(0) to the chelate effect

The structure of (diphos)Mo(CO)₄ (diphos=1,2- bis(diphenylphosphino)ethane) has been determined by single crystal X-ray crystallography. The crystals are orthorhombic with a=22.600(8), b=16.799(4) and c=14.587(4) Å, space group Pbca, D_calc.=1.45 g cm⁻³ and Z=8. The structure was solved by the Patterson technique and refined by full-matrix least- squares methods to R=0.044 using 2206 reflections measured on a four-circle diffractometer. The coordination about the central molybdenum atom is a distorted octahedron, the greatest deviation from ideal geometry being the P1-Mo-P2 angle (80.2(1)°). Other distortions are induced through steric interaction between the phenyl and the carbonyl groups. The structure of (diphos)Mo(CO)4 is compared to that previously reported for cis- (MePh₂P)₂Mo(CO)₄; the two molecules differ only that two methyl groups of the latter complex are replaced by the CH₂CH₂ backbone in the former. The influence of this difference is discussed both in terms of molecular distortions induced by the presence of the chelate ring and their influence on reactivity via chelate ring-opening and -closure.     

Reactivities of the coordinated organonitriles in molybdenum(0) and tungsten(0) phosphine complexes: protonation of the nitrile carbon and cleavage of the CN triple bond

The molybdenum and tungsten dinitrogen-organonitrile complexes trans-[M(N₂)(NCR)(dppe)₂] (2, M=Mo; 4, M=W; R=Ph, C₆H₄Me-p, C₆H₄OMe-p, Me; dppe=Ph₂PCH₂CH₂PPh₂) underwent double protonation at the nitrile carbon atom with loss of N₂ and a change in oxidation state to +4 on treatment with hydrochloric acid to afford the cationic imido complexes trans-[MCl(NCH₂R)(dppe)₂]⁺. The solid-state structure of trans-[WCl(NCH₂CH₃)(dppe)₂][PF₆]·CH₂Cl₂ was determined by single-crystal X-ray analysis. Protonation of complexes 2 by fluoroboric acid or hydrobromic acid also formed the similar imido complexes trans-[MoX(NCH₂R)(dppe)₂]⁺ (X=F, Br). In contrast, the dinitrogen complex trans-[Mo(N₂)₂(dppe)₂] reacted with two equiv. of benzoylacetonitrile, a nitrile with acidic CH hydrogen atoms, to give the nitrido complex trans-[Mo(N)(NKCCHCOPh)(dppe)₂] (12), which was accompanied by evolution of dinitrogen and the formation of 1-phenyl-2-propen-1-one in high yields. For complex 12, the zwitterionic structure, where the anionic enolate ligand PhC(O⁺)=CHCN coordinates to the cationic Mo(IV) center through its nitrogen atom, was confirmed by spectroscopic measurements and single-crystal X-ray analysis. A unique intermolecular aromatic C---HO hydrogen bonding was observed in that crystal structure. Complex 12 is considered to be formed via the cleavage of the CN triple bond of benzoylacetonitrile on the metal. A reaction mechanism is proposed, which includes the double protonation of the nitrile carbon atom of the ligating benzoylacetonitrile on a low-valent molybdenum center.     

Coordinated 2-halo-1,3,2-dioxaphosphorinane ligands. II. Syntheses and 13C, 31P and 95Mo NMR and IR spectroscopic characterization of some Cr and Mo pentacarbonyl complexes of 2-substituted-4-methyl-1,3,2-dioxaphosphorinanes

A study of the reactions of M(CO)₅(P(OCH₂CH₂CH(Me)O)Cl) (M=Cr, Mo) with a variety of nucleophiles of the type HER (E=NH, O, S; R=H, alkyl, aryl) is reported. The ¹³C, ³¹P and ⁹⁵Mo NMR and IR spectral data for the M(CO)₅(P(OCH₂CH₂CH(Me)O)ER) complexes is presented and compared to that previously reported for some Mo(CO)₅(P(OCH₂CMe₂CH₂O)ER) complexes. This comparison provides insight into the manner in which variations in the metal and in the substitution on the 1,3,2-dioxaphosphorinane ring affect the electron density distribution within these complexes.The results from a study of the rates of chloride substitution by n-propylamine in the M(CO)_s(P(OCH₂CH₂CH(Me)O)Cl) complexes are also presented. These rates are compared with those previously reported for chloride substitution by n-propylamine in the Mo(CO)₅(P(OCH₂CMe₂CH₂O)Cl) and Mo(CO)₅(Ph₂PCl) complexes. These comparisons, in conjunction with the NMR and IR studies, suggest that both the position of the Me groups on the phosphorinane ring and the amount of electron density on the P have significant effects upon the rate of chloride substitution in these complexes.     

Synthesis and some reactivity of amidinato(pyridine) complexes of molybdenum and tungsten formulated as [M(η-allyl)(amidinato)(CO)2(NC5H5)]

Bis(pyridine) complexes of molybdenum and tungsten, [M(η³-allyl)Cl(CO)₂(NC₅H₅)₂] (M=Mo; 3-Mo, M=W; 3-W), reacted with an equimolar amount of lithiated amidinate, Li[(PhN)₂CR] (R=H; 4a-Li, R = CH₃; 4b-Li), to yield corresponding amidinato(pyridine) complexes, [M(η³-allyl){(PhN)₂CR}(CO)₂(NC₅H₅)] (M=Mo, R=H; 5a-Mo, M=Mo, R=CH₃; 5b-Mo, M=W, R=H; 5a-W), as a yellow solid. The dissociation of pyridine ligand from the central metal in complexes 5a was observed in a polar solvent such as acetonitrile. In these cases, although the formation of amidinato(acetonitrile) complexes, [M(η³-allyl){(PhN)₂CH}(CO)₂(NCMe)] (M=Mo; 6a-Mo, M=W; 6a-W), was suggested spectroscopically, isolation of complexes 6a was not successful but the re-formation of pyridine complexes 5a was observed. In the reactions of complexes 5a with PEt₃ and with P(OMe)₃, the substitution reactions easily took place to give [M(η³-allyl){(PhN)₂CH}(CO)₂(PEt₃)] (M=Mo; 7a-Mo, M=W; 7a-W) and [M(η³-allyl){(PhN)₂CH}(CO)₂{P(OMe)₃}] (M=Mo; 8a-Mo, M=W; 8a-W), respectively. These complexes were characterized spectroscopically as well as, in some cases, by X-ray analyses.     

Self assembly of a Fe(L) complex with octacyano metallates [M(CN)8] (L = pentadentate macrocyclic ligand, M = Mo, W): Crystal structure and magnetic properties

The self assembly of [Fe^III(L)]Cl₂ClO₄ (L = pentadentate macrocyclic ligand) with octacyano metallates [M^IV(CN)₈]⁴⁻ (M = Mo, W) leads to bimetallic cyano-bridged 2-D coordination polymers of formula [{Fe(L)}₃{M(CN)₈}₂]Cl·xH₂O with M = Mo (2), or W (3). The structure of the tungsten analogue has been established by single crystal X-ray diffraction. The magnetic properties for both Mo and W derivative are reported.     

Carbonyl complexes of Rh(I), Ir(I) and Mo(0) containing substituted derivatives of 1,10-phenanthroline and 2,2′-bipyridine

The A₁ symmetry v_CO of the carbonyl complexes [Mo(chel)(CO)₄], [M(chel)(CO)₂] [PF₆] (M=Rh, Ir; chel=bipy, phen and substituted derivatives) are used for determining the electron donor-acceptor properties of the title ligands. The steric hindrance of the methyl groups in positions 2 and 9 of the phenanthroline favours the formation of Rh(I) and Ir(I) pentacoordinated derivatives.     

Electronic absorption spectra of cis-M(CO)2(α-diimine)2 complexes (M = Mo or W; α-diimine = 2,2′-bipyridine or 1,10-phenanthroline)

Syntheses, infrared spectra, and electronic absorption spectra of cis-M(CO)₂(α-diimine)₂ (M = Mo, W; α-diimine = 2,2′-bipyridine, 1,10-phenanthroline) complexes are reported. Infrared spectra indicate carbonyl stretching frequencies in the 1700–1800 cm⁻¹ region, consistent with strong M(dπ) → (π*)CO back-bonding in these dicarbonyl complexes. Electronic absorption spectra illustrate several intense M(dπ) → (π*)α-diimine transitions throughout the visible region. A comparison of the solvent effects on the absorption spectra of the cis-M(CO)₂(α-diimine)₂ species is made with the well known M(CO)₄(α-diimine) complexes.     

Improved preparation of indenyl molybdenum(II) and tungsten(II) compounds

Oxidative addition of 1-bromo-1H-indene to [Mo(CO)₃(NCMe)₃] and [W(CO)₃(NCEt)₃] is a suitable method for preparation of the indenyl compounds [IndMo(CO)₃Br] and [IndW(CO)₃Br], respectively. These products were fully characterised using spectroscopic methods. Structure of [IndW(CO)₃Br] was determined by single crystal X-ray diffraction analysis.     

Synthesis of bent titanocene metalloligands with the (diphenylphosphino)tetramethylcyclopentadienyl moiety. X-ray structure of [(η-C5Me4 2)2TiCl2]Mo(CO)4

The reactions of lithium(diphenylphosphino)tetramethylcyclopentadienide with CpTiCl₃ and secondly with TiCl₃ followed by CCl₄ oxidation lead to the formation of two titanocene phosphines: (η⁵-C₅H₅)[η⁵-C₅Me₄P(C₆H₅)₂]TiCl₂ (2) and [η⁵-C₅Me₄P(C₆H₅)₂]₂TiCl₂ (3), respectively. The metalloligand 3 reacts readily with Mo(CO)₄cod, Mo(CO)₅THF and Mo(CO)₆ to give in each case [(η⁵-C₅Me₄ o(CO)₄ (6) as a sole product. The structure of 6 has been determined by X-ray diffraction. Crystal data: P , a = 11.716(1), b = 11.753(2), c = 16.110(2) Å, α = 99.06(1), β = 92.61(1), γ = 104.20(1)°, Z = 2. The molybdenum-titanium distance of 5.194(1) Å rules out any metal-metal interaction. The chlorine substitution reactions by CO in 2 and 3 and by thiolate group (pH₃C-C₆H₄-S) in 16 are reported.     

Haloalkyl complexes of the transition metals. Part 5. The synthesis and reactions of some new pentamethylcyclopentadienyl halomethyl and methoxymethyl complexes of molybdenum(II) and tungsten(II) and the X-ray crystal structure of the cationic ylide complex [η-C5Me5W(CO)3CH2PPh3]I

Synthetic routes are described for the new halo- methyl complexes of the type [η-C₅Me₅M(CO)₃- CH₂X]. The complexes where M = Mo, X = Cl or OMe and M = W, X = Cl, I, OMe have been fully characterized. Reaction of [η-C₅Me₅Mo(CO)₃CH₂Cl] with PPh₃ in methanol under reflux or acetonitrile at room temperature gives [η-C₅Me₅Mo(CO)₂(PPh₃)- Cl], whereas reaction of [η-C₅Me₅W(CO)₃CH₂I] with PPh₃ under similar conditions gives the cationic phosphorus ylide complex [η-C₅Me₅W(CO)₃CH₂- PPh₃]I. The structure of this ylide complex has been determined by X-ray crystallography. The complex crystallizes with half a molecule of CH₂Cl₂ in the monoclinic space group P2₁/n with a = 16.616- (8), b = 11.738(6), c = 18.126(9) Å, β = 101.74(2)° and Z = 4. The structure was solved and refined to R = 0.076. It confirms the formulation of the compound and the presence of the ylide ligand, WC_ylide 2.34(2) Å, PC_ylide 1.82(2) Å and the WC_ylideP angle of 119(1)°.