Mixed-metal butterfly acetamidediato clusters derived from a highly reactive ruthenium oxo cluster: synthesis and characterization of [(PPh3)2N][MRu3(CO)12(η-μ3-NC(μ-O)CH3)], (M = Mn or Re)

Analogy with the isolable oxo cluster [Fe₃(CO)₉(μ₃-O)]²⁻, which is structurally interesting and synthetically useful, prompted the present attempt to synthesize its ruthenium analog. Although the high reactivity of [Ru₃(CO)₉(μ₃-O)]²⁻ (I) prevented its isolation, the reaction of this species with [M(CO)₃(NCCH₃)]⁺, where M = Mn or Re, yields [PPN][MRu₃(CO)₁₂(η²-μ₃-NC(μ-O)CH₃]⁻. The high nucleophilicity of the oxo ligand in [Ru₃(CO)₉(μ₃-O)]²⁻ (I) appears to be responsible for the conversion of acetonitrile to an acetamidediato ligand and for the instability of I. The crystal structure of [PPN][MnRu₃(CO)₁₂(η²-μ₃-NC(μ-O)CH₃)]] reveals a hinged butterfly array of metal atoms in which the acetamidediato ligand bridges the two wings with μ₃-N bonding to an Mn and two Ru atoms, and μ-O bonding to an Ru atom.     

Chemistry of vinylidene complexes XI. Synthesis of trinuclear MnFePt complexes by means of consecutive assembling out of mono- and dimetal vinylidene precursors

The dimetal μ-vinylidene complexes Cp(CO)₂MnPt(μ-C = CHPh)L₂ (L = tert.-phosphine or -phosphite), which have been obtained by coupling of the mononuclear complex Cp(CO)₂Mn=C=CHPh and unsaturated PtL₂ unit, add smoothly the Fe(CO)₄ moiety to produce trimetal MnFePt compounds. The μ₃-vinylidene cluster CpMnFePt(μ₃-C=CHPh)(CO)₆(PPh₃) was prepared in quantitative yields from the reactions of Cp(CO)₂MnPt(μ-C=CHPh)(PPh₃)L (L = PPh₃ or CO) with Fe₂(CO)₉ in benzene at 20 °C. The phosphite-substituted complexes Cp(CO)₂Mnpt(μ-C=CHPh)L₂ (L = P(OEt)₃ or P(OPrⁱ)₃) react under analogous conditions with Fe₂(CO)₉ to give mixtures (2:3) of the penta- and hexacarbonyl clusters, CpMnFePt(μ₃-C = CHPh)(CO)₅L₂ and CpMnFePt(μ₃-C = CHPh)(CO)₆L, respectively. The similar reaction of the dimetal complex Cp(CO)₂MnPt(μ-C = CHPh)(dppm), in which the Pt atom is chelated by dppm = Ph₂PCH₂PPhPin2 ligand, gives only a 15% yield of the analogous trimetal μ₃-vinylidene hexacarbonyl product CpMnFePt(μ₃-C = CHPh)(CO)(dppm), but the major product (40%) is the tetranuclear μ₄-vinylidene cluster (dppm)PtFe₃(μ₄-C = CHPh)(CO)₉. The IR and ¹H, ¹³C and ³¹P NMR data for the new complexes are reported and discussed.     

Substitution reaction mechanisms of dihydrido-ruthenium(II) phosphine complexes: hydribe basicity and molecular hydrogen intermediates

Kinetic and activation parameter data for the reactions of cct-Ru(H)₂(CO)₂(PPh₃)₂ (1) (cct = cis, cis, trans) in THF with thiols, CO and PPh₃ to give cct-RuH(SR)(CO)₂(PPh₃)₂, Ru(CO)₃(PPh₃)₂ and Ru(CO)₂(PPh₃)₂, respectively, reveal a common, rate-determining step, the initial dissociation of H₂ from 1; the activated complex probably resembles the corresponding Ru(η²-H₂) species. Reaction of Ru(H)₂(dppm)₂ (2) (as a cis/trans mixture, DPPM = bis(diphenylphosphino)methane) with thiols initially generated cis- and trans- RuH(SR) (dppm)₂ with a rate that depends on both the type and concentration of thiol. The higher basicity of the hydride ligands in 2 (versus 1), which is demonstrated by deuterium exchange with CD₃OD, gives rise in the thiol reaction to an initial protonation step prior to loss of H₂. A species detected in the thiol reaction is possibly [RuH(η²-H₂ (dppm)₂]², the anticipated intermediate for this reaction and for the hydrogen exchange with alcohol. A longer reaction of 2 with PhCH₂SH gives solely cis-Ru(SCH₂Ph)₂(dppm)₂.     

Chelated alkyl halide manganese complexes (η:η-C5H4CH2CH2X)Mn(CO)2 from photolysis of (η-C5H4CH2CH2X)Mn(CO)3

Manganese tricarbonyl complexes (η⁵-C₅H₄CH₂CH₂Br)Mn(CO)₃ (3) and (η⁵-C₅H₄CH₂CH₂I)Mn(CO)₃ (4), with an alkyl halide side chain attached to the cyclopentadienyl ligand, were synthesized as possible precursors to chelated alkyl halide manganese complexes. Photolysis of 3 or 4 in toluene, hexane or acetone-d₆ resulted in CO dissociation and intramolecular coordination of the alkyl halide to manganese to produce (η⁵:η¹-C₅H₄CH₂CH₂Br)Mn(CO)₂ (5) and (η⁵:η¹-C₅H₄CH₂CH₂I)Mn(CO)₂ (6). Low temperature NMR and IR spectroscopy established the structures of 5 and 6. Photolysis of 3 in a glass matrix at 91 K demonstrated CO release from manganese. Low temperature NMR spectroscopy established that the coordinated alkyl halide complexes are stable to approximately −20°C.     

Synthesis and reactivity of coordinatively unsaturated osmium and ruthenium stannyl complexes

Treatment of MHCl(CO)(PPh₃)₃ (M=Ru, Os) with (CH₂=CH)SnR₃ is a good general route to the coordinatively unsaturated osmium and ruthenium stannyl complexes M(SnR₃)Cl(CO)(PPh₃)₂ (1: M=Ru, R=Me; 2: M=Ru, R = n-butyl; 3: M=Ru, R = p-tolyl; 4: M=Os, R=Me). These coordinatively unsaturated complexes readily add CO and CN-p-tolyl to form the coordinatively saturated compounds M(SnR₃)Cl(CO)L(PPh₃)₂ (5: M=Ru, R=Me, L=CO; 6: M=;Ru, R = n-butyl, L=CO; 7: M=Ru, R = p-tolyl, L=CO; 8: M=Os, R=Me, L=CO; 9: M=Ru, R=Me, L=CN-p-tolyl; 10: M=Ru, R = n-butyl, L=CN-p-tolyl; 11: M=Os, R=Me, L=CN-p-tolyl). In addition, the chloride ligand in Ru(SnR₃)Cl(CO)(PPh₃)₂ proves to be labile and treatment with the potentially bidentate anionic ligands, dimethyldithiocarbamate or diethyldithiocarbamate, affords the coordinatively saturated compounds Ru(SnR₃)(η²-S₂CNR′₂)(CO)(PPh₃)₂ (12: R=Me, R′ = Me; 13: R=Me, R′ = Et; 14: R = n-butyl, R′ = Me; 15: R = p-tolyl, R′ = Me; 16: R = p-tolyl, R′ = Et). Chloride is also displaced by carboxylates forming the six-coordinate compounds Ru(SnR₃)(η²-O₂CR′)(CO)(PPh₃)₂ (17: R=Me, R′ = H; 18: R=Me, R′ = Me; 19: R=Me, R′ = Ph; 20: R = n-butyl, R′ = Me; 21: R = p-tolyl, R′ = Me). IR and ¹H NMR spectral data for all the new compounds and ³¹P and ¹¹⁹Sn NMR spectral data for selected compounds are reported.     

Heterobimetallic chloro bridgedcomplexes of (η:η−C10H16)-ruthenium(IV) with palladium(II), platinum(II), rhodium(III), iridium(III), copper(I) and rhodium(I)

Metathesis of [(η³:η³−C₁₀H₁₆)Ru(Cl) (μ−Cl)]₂ (1) with [R₃P) (Cl)M(μ-Cl)]₂ (M = Pd, Pt), [Me₂NCH₂C₆H₄Pd(μ-Cl)]₂ and [(OC)₂Rh(μ-Cl)]₂ affords the heterobimetallic chloro bridged complexes (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂M(PR₃)(Cl) (M = Pd, Pt), (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂PdC₆H₄CH₂NMe₂ and (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂Rh(CO)₂, respectively. Complex 1 reacts with [Cp^*M(Cl) (μ-Cl)]₂ (M = Rh, Ir), [p-cymene Ru(Cl) (μ-Cl]₂ and [(Cy₃P)Cu(μ-Cl)]₂ to give an equilibrium of the heterobimetallic complexes and of educts. The structures of (η³:η³-C₁₀H₁₆)Ru(μ-Cl)₂Pd(PR₃) (Cl) (R = Et, Bu) and of one diastereoisomer of (η³:η³-C₁₀H₁₆)Ru(μ-Cl)₂IrCp^*(Cl) were determined by X-ray diffraction.     

Silicon-containing carbene complexes 16. Intramolecular agostic stabilization versus nucleophilic addition to the 16-electron carbene complex (CO)4(L)W=C(NMe2)SiPh2Me

The 16-electron complex (CO)₄W=C(NMe₂)SiPh₂Me (1) was photochemically prepared from (CO)₅W=C- (NMe2)SiPh₂Me. Reactions with selected nucleophiles, having different ligand properties, were performed to test the strength of the intramolecular agostic interaction of one of the phenyl groups, by which 1 is stabilized. The stable complexes cis-(CO)₄LW=C(NMe₂)SiPh₂Me were formed with L=P(OMe)₃, P(OEt)₃ or 2,6-Me₂C₆H₃NC. The substituted complexes had no tendency for ligand elimination. Addition of acetonitrile or pyridine to an ether solution of 1 resulted in the formation of cis-(CO)₄(MeCN)W=C(NMe₂)SiPh₂Me or cis-(CO)₄(C₅H₅N)- W=C(NMe₂)SiPh₂Me, respectively. These reactions were reversed on evaporation of the solutions. No reaction was observed with triethylamine.     

Control of the migratory aptitudes of vinyl and aryl ligands in ruthenium(II) complexes

Complexes Ru(CO)₂ (CH=CHR) (C₆H₄X-4)L₂ (R=^tBu, Ph, OEt; X=H, Cl, OMe; L=PMe₃, PMe₂Ph, P(OMe)₂Ph) in which the two phosphorus ligands are mutually cis (isomer 1) react readily with ligands ^tBuNC, CO and P(OMe)₃ to give complexes in which one of the organic ligands has migrated onto a carbonyl ligand. Vinyl migration products (5) retain the mutually cis geometry of the phosphorus ligands, and are unstable: one of the decomposition products is the ketone RCH=CHC(O)C₆H₄X-4. Phenyl migration products (4) are stable and have the phosphorus ligands in mutually trans positions; an X-ray crystal structure of Ru(CO) (CN^tBu) {C(O)Ph} (CH=CHPh) (PMe₂Ph)₂ was obtained. In both cases, the incoming ligand enters trans to the newly formed acyl ligand. Vinyl migration is favoured over aryl migration by electron-donating substituents on the vinyl ligand, electron-withdrawing substituents on the aryl ligand, good σ-donor phosphorus ligands and use of ^tBuNC as the incoming ligand. The rate of phenyl migration in Ru(CO)₂(CH=CHPh)Ph(PMe₂Ph)₂ is independent of ^tBuNC concentration: k=1.5 × 10⁻³ s⁻¹ at 20°C. Isomer 3 of complexes Ru(CO)₂(CH=CHR) (C₆H₄X-4)L₂ in which the phosphorus ligands are mutually trans is much less reactive towards migration reactions. The reactivity of isomer 1 is attributed to the steric strain of two mutually cis phosphorus ligands.     

Synthesis, characterization, and reactivity of organometallic Zr(IV) carboxylate complexes

A series of zirconium(IV) complexes, [ZrX₂(XDK)], where XDK is the constrained carboxylate ligand m-xylylenediamine bis(Kemp's triacid imide), were prepared and structurally characterized. The solid state structure of the mononuclear carboxylate alkyl complex [Zr(CH₂Ph)₂(XDK)] reveals that one benzyl group is bonded in an η²-fashion to the metal center. The reactivity of [Zr(CH₂Ph)₂(XDK)] displays its electrophilic character toward nucleophiles strong enough to displace the η²-benzyl group. Thus, weak sigma donor ligands such as CO, alkynes and anilines do not react, whereas strong sigma donors, such as pyridines and isocyanides, rapidly form the monoadduct [Zr(CH₂Ph)₂(4-tert-butylpyridine)(XDK)] and [Zr{η²-2,6-Me₂PhNCCH₂Ph}₂(XDK)], an η²-iminoacyl derivative, respectively. Attempts to prepare zirconium amido complexes with H₂XDK generally afforded the eight-coordinate [Zr(XDK)₂] complex but use of the small amido ligand precursorZr(NMe₂)₄ allowed [Zr(NMe₂)₂(4-tert-butylpyridine)(XDK)] to be isolated in good yield.     

Tin and thallium reagents for transfer of the 1,2-di-tert-butylcyclopentadienyl ligand to transition metals

New tin and thallium reagents capable of transferring the 1,2-di-tert-butylcyclopentadienyl moiety are easily prepared and utilized in furthering the transition metal organometallic chemistry of this intersting ligand. Lithium 1,2-di-tert-butylcyclopentadienide (1) reacts cleanly and selectively with SnClMe₃ to give 2,3-di-tert-butyl-5-trimethylstannyl-1,3-cyclopentadiene (2), which in turn reacts with Re(CO)₅Br to form the half-sandwich complex [Re(η⁵-C₅H₃(1,2-Bu^t)₂)(CO)₃] (3). The reaction between thallium ethoxide and 1,5-ditert-butyl-1,3-cyclopentadiene in hexane affords the excellent cyclopentadienyl transfer reagent, thallium 1,2-di-tert-butylcyclopentadienide (4). The thallium salt reacts with [Ru(COD)Cl₂]_n to give the sandwich complex [Ru(η⁵-C₅H₃(1,2-Bu₂^t)₂)] (5).     

Reactivity, variable temperature solution H NMR studies and MO calculations of dimolybdenum allenylidene complexes of the type [(η-C5H5)2Mo2(CO)4(μ,η(4e)-C=C=CR1R2)]

The reactivity, towards nucleophiles and electrophiles, of dimolybdenum allenylidene complexes of the type [Cp₂Mo₂(CO)₄(μ,η²(4e)-C=C=CR1R2)] (Cp=η⁵-C₅H₅) has been investigated. The nucleophilic attacks occur at the C_γ carbon atom, while electrophiles affec the C atom. Variable temperature solution ¹H NMR studies show a dynamic behavior of these complexes consisting of an equilibrium between two enantiomers with a symmetrical [Cp₂Mo₂(CO)₄(μ-σ,σ(2e)-C=C=CR1R2)] transition state. Extended Hückel MO calculations have been carried out on the model [Cp₂Mo₂(CO)₄(μ,η²-C=C=CH₂]. The calculated charges of the allenylidene carbon atoms suggest that the electrophilic attacks are under charge control, while the nucleophilic attacks are rather under orbital control.     

The synthesis and reactions of A-ring aromatic steroid complexes of manganese tricarbonyl

Treatment of the A-ring aromatic steroids estrone 3-methyl ether and β-estradiol 3, 17-dimethyl ether with Mn(CO)₅⁺BF₄⁻ in CH₂Cl₂ yields the corresponding [(steroid)Mn(CO)₃]BF₄ salts 1 and 2 as mixtures of and β isomers. The X-ray structure of [(estrone 3-methyl ether)Mn(CO)₃]BF₄ · CH₂Cl₂ (1) having the Mn(CO)₃ moiety on the side of the steroid is reported: space group P2₁ with a=10.3958(9), b=10.9020(6), c=12.6848(9) Å, β=111.857(6)°, Z=2, V=1334.3(2) ų, _calc=.481 cm⁻³, R=0.0508, and wR=0.0635. The molecule has the traditional ‘piano stool’ structure with a planar arene ring and linear Mn---C---O linkages. The nucleophiles NaBH₄ and LiCH₂C(O)CMe₃ add to [(β-estradiol 3,17-dimethyl ether)Mn(CO)₃]BF₄ (2) in high yield to give the corresponding - and β-cyclohexadienyl manganese tricarbonyl complexes (3). The nucleophiles add meta to the arene -OMe substituent and exo to the metal. The and β isomers of 3 were separated by fractional crystallization and the X-ray structure of the β isomer with an exo-CH₂C(O)CMe₃ substituent is reported (complex 4): space group P2₁2₁2₁ with a=7.5154(8), b=15.160(2), c=25.230(3) Å, Z=4, V=2874.4(5) ų, _calc=1.244 g cm⁻³, R=0.0529 and wR2=0.1176. The molecule 4 has a planar set of dienyl carbon atoms with the saturated C(1) carbon being 0.592 Å out of the plane away from the metal. The results suggest that the manganese-mediated functionalization of aromatic steroids is a viable synthetic procedure with a range of nucleophiles of varying strengths.     

Synthesis and properties of the dichloro [tetramethyl (trifluoromethyl)cyclopentadienyl]ruthenium dimer: X-ray structure of [M2(η-C5Me4CF3)2Cl2(μ-Cl)2] (M=Ru, Rh)

The reaction of RuCl₃(H₂O), with C₅Me₄CF₃J in refluxing EtOH gives [Ru₂(η⁵-C₅Me₁CF₂)₂ (μ-Cl₂] (20 in 44% yield. Dimer 2 antiferromagnetic (−2J=200 cm¹). The crystal structures of 2 (rhombohedral system, R3 space group, Z=9, R=0.0589) and [Rh₂(η⁵-C₅Me₄CF₃(₂Cl₂(μ-Cl)₂] (3) (rhombohedral system. space group, Z = 9, R = 0.0641) were solved; both complexes have dimeric structures with a trans arrangement of the η⁵-C₅Me₄CF₄ rings. Comparison of the geometry of 2 and 3 with those of the corresponding η⁵-C₅Me₅ complexes shows that lowering the ring symmetry causes significant distortion of the M₂(μ-Cl)₂ moiety. The analysis of the MCl₃ fragment conformations in 2 and 3 and in the η⁵-C₅ME₅ analogues shows that they are correlated with the M---M distances. The Cl atoms are displaced by Br on reaction of 2 with KBr in MeOH to give the diamagnetic dimer [Ru₂(η⁵-C₅Me₄CF₃)₂Br₂ (μ-Br₂] (4). Complex 2 reacts with O₂ in CH₂Cl₂ solution at ambient temperature to form a mixture of isomeric η⁶-fulvene dimers [Ru₂(η⁶-C₅Me₃CF₃ = CH₂)₂Cl₂(μ-Cl)₂] (5). Reactions of 5 with CO and allyl chloride give Ru(η⁵-C₅Me₃CF₃CH₂Cl)(CO)₂Cl (6) and Ru(η⁵-C₅Me₃CF₃CF₃CH₂Cl)(η³-C₃H₅)Cl₂ (7) respectively.     

Kinetics and mechanisms of ligand substitution reactions of molybdenum SO2 complexes. Synthesis and X-ray structure of trans-Mo(CO)2 (dmpe) (PPh3) (SO2)

Kinetic results are reported for intramolecular PPh₃ substitution reactions of Mo(CO)₂(η¹-L)(PPh₃)₂(SO₂) to form Mo(CO)₂(η²-L)(PPh₃)(SO₂) (L = DMPE = (Me)₂PC₂H₄P(Me)₂ and dppe=Ph₂PC₂H₄PPh₂) in THF solvent, and for intermolecular SO₂ substitutions in Mo(CO)₃(η²-L)(η²-SO₂) (L = 2,2′-bipyridine, dppe) with phosphorus ligands in CH₂Cl₂ solvent. Activation parameters for intramolecular PPh₃ substitution reactions: ΔH^≠ values are 12.3 kcal/mol for dmpe and 16.7 kcal/mol for dppe; ΔS^≠ values are −30.3 cal/mol K for dmpe and −16.4 cal/mol K for dppe. These results are consistent with an intramolecular associative mechanism. Substitutions of SO₂ in MO(CO)₃(η²-L)(η²-SO₂) complexes proceed by both dissociative and associative mechanisms. The facile associative pathways for the reactions are discussed in terms of the ability of SO₂ to accept a pair of electrons from the metal, with its bonding transformations of η²-SO₂ to η¹-pyramidal SO₂, maintaining a stable 18-e count for the complex in its reaction transition state. The structure of Mo(CO)₂(dmpe)(PPh₃)(SO₂) was determined crystallographically: P2₁/c, A=9.311(1), B = 16.344(2), C = 18.830(2) Å, ß=91.04(1)°, V=2865.1(7) ų, Z=4, R(F)=3.49%.     

Mono-η complexes of chromium(II) and chromium(0). Electron demanding substituents, structural and spectroscopic data comparisons

Using thermal and photochemical methods a series of new chromium complexes has been prepared: (ν⁶-p-C₆H₄F₂)Cr(CO)₃; (ν⁶-C₆H₅CF₃)Cr(CO)₃; [m-C₆H₄(CF₃)₂]Cr(CO)₃; (ν⁶-C₆H₅F)Cr(CO)₂H(SiCl₃); (ν⁶-C₆H₅F)Cr(CO)₂(SiCl₃)₂; (p-C₆H₄F₂)Cr(CO)₂-H(SiCl₃); (C₆H₅CF₃)Cr(CO)₂H(SiCl₃(p-C₆H₄F₂)Cr(CO)₂(SiCl₃)₂; C₆H₅CF₃)Cr(CO)₂(SiCl₃)₂; [m-C₆H₄(CF₃)₂]Cr(CO)₂-H(SiCl₃); [m-C₆H₄(CF₃)₂]Cr(CO)₂(SiCl₃)₂. Two compounds were structurally characterized by X-ray diffraction. These data combined with IR and ¹H NMR have allowed assessment of some of the electronic and steric effects. The Cr-arene bond is considerably longer in the Cr(II) derivatives than in the Cr(0) species. Also the Cr center, as might be expected, is less electron rich in the Cr(II) dicarbonyl disilyl derivatives. The ν⁶-p-C₆H₄F₂ ligands are slightly folded so that the C---F carbons are moved further away from the Cr center. Comparison of structural and electronic effects is made with a series of similar chromium compounds reported in the literature. These new (arene)Cr(II) derivatives possess more labile ν⁶-arene ligands, which promise a rich chemistry at the chromium center.     

Model reactions of a carbonylation catalyst: phosphite induced migratory CO insertion in [MeIr(CO)2I3]

Carbonylation of the anionic iridium(III) methyl complex, [MeIr(CO)₂I₃]⁻ (1) is an important step in the new iridium-based process for acetic acid manufacture. A model study of the migratory insertion reactions of 1 with P-donor ligands is reported. Complex 1 reacts with phosphites to give neutral acetyl complexes, [Ir(COMe)(CO)I₂L₂] (L = P(OPh)₃ (2), P(OMe)₃ (3)). Complex 2 has been isolated and fully characterised from the reaction of Ph₄As[MeIr(CO)₂I₃] with AgBF₄ and P(OPh)₃; comparison of spectroscopic properties suggests an analogous formulation for 3. IR and ³¹P NMR spectroscopy indicate initial formation of unstable isomers of 2 which isomerise to the thermodynamic product with trans phosphite ligands. Kinetic measurements for the reactions of 1 with phosphites in CH₂Cl₂ show first order dependence on [1], only when the reactions are carried out in the presence of excess iodide. The rates exhibit a saturation dependence on [L] and are inhibited by iodide. The reactions are accelerated by addition of alcohols (e.g. 18× enhancement for L = P (OMe)₃ in 1:3 MeOH-CH₂Cl₂). A reaction mechanism is proposed which involves substitution of an iodide ligand by phosphite, prior to migratory CO insertion. The observed rate constants fit well to a rate law derived from this mechanism. Analysis of the kinetic data shows that k₁, the rate constant for iodide dissociation, is independent of L, but is increased by a factor of 18 on adding 25% MeOH to CH₂Cl₂. Activation parameters for the k₁ step are ΔH^≠ = 71 (±3) kJ mol⁻, ΔS^≠ = −81 (±9) J mol⁻¹ K⁻¹ in CH₂Cl₂ and ΔH^≠ = 60(±4) kJ mol⁻¹, ΔS^≠ = −93(± 12) J mol⁻¹ K⁻¹ in 1:3 MeOH-CH₂Cl₂. Solvent assistance of the iodide dissociation step gives the observed rate enhancement in protic solvents. The mechanism is similar to that proposed for the carbonylation of 1.     

The new enneanuclear nickel carbonyl anion [Ni9(CO)16] and its relationships with the [Ni12(CO)21] and [Ni6Rh3(CO)17] clusters

The reaction of [N(PPh₃)₂]₂[Ni₆(CO)₁₂] with Cu(PPh₃)_xCl (x=1, 2), as well as the degradation of [N(PPh₃)₂]₂[H₂Ni₁₂(CO)₂₁] with PPh₃, affords the new and unstable dark orange–brown [N(PPh₃)₂]₂[Ni₉(CO)₁₆].THF salt in low yields. This salt has been characterized by a CCD X-ray diffraction determination, along with IR spectroscopy and elemental analysis. The close-packed two-layer metal core geometry of the [Ni₉(CO)₁₆]²⁻ dianion is directly related to that of the bimetallic [Ni₆Rh₃(CO)₁₇]³⁻ trianion and may be envisioned to be formally derived from the hcp three-layer geometry of [Ni₁₂(CO)₂₁]⁴⁻ by the substitution of one of the two outer [Ni₃(CO)₃(μ−CO)₃]²⁻ layers with a face-bridging carbonyl group.     

Slippage of η-allenyl/propargyl to an η structure and tautomerization of η-propargyl to η-allenyl in ligand addition and substitution reactions of platinum(II) complexes

Reactions of [(PPh₃)₂Pt(η³-CH₂CCPh)]OTf with each of PMe₃, CO and Br⁻ result in the addition of these species to the metal and a change in hapticity of the η³-CH₂CCPh to η¹-CH₂CCPh or η¹-C(Ph)=C=CH₂. Thus, PMe₃ affords [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]⁺, CO gives both [trans-(PPh₃)₂Pt(CO)(η¹-CH₂CCPh)]⁺ and [trans-(PPh₃)₂Pt(CO)(η¹-C(Ph)=C=CH₂)]⁺, and LiBr yields cis-(PPh₃)₂PtBr(η¹-CH₂CCPh), which undergoes isomerization to trans-(PPh₃)₂PtBr(η¹-CH₂CCPh). Substitution reactions of cis- and trans-(PPh₃)₂PtBr(η¹-CH₂CCPh) each lead to tautomerization of η¹-CH₂CCPh to η¹-C(Ph)=C=CH₂, with trans-(PPh₃)₂PtBr(η¹-CH₂CCPh) affording [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]⁺ at ambient temperature and the slower reacting cis isomer giving [trans-(PPh₃)(PMe₃)₂Pt(η¹-C(Ph)=C=CH₂)]⁺ at 54 °C . All new complexes were characterized by a combination of elemental analysis, FAB mas spectrometry and IR and NMR (¹H, ¹³C{¹H} and ³¹P{¹H}) spectroscopy. The structure of [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]BPh₄·0.5MeOH was determined by single-crystal X-ray diffraction analysis.     

Ligand induced P---H bond formation and a comparison of the reactivity of two isomers of the carbonyl hydride [Pt2(μ-PBu2)2(H)(CO)(PBu2H)]CF3SO3

The Pt₂ ^(II) isomeric terminal hydrides [(CO)(H)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)]CF₃SO₃ (1a), and [(CO)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)(H)]CF₃SO₃ (1b), react rapidly with 1 atm of carbon monoxide to give the same mixture of two isomers of the Pt₂ ^(I) dicarbonyl [Pt₂(μ-PBu^t ₂)(CO)₂(PBu^t ₂H)₂]CF₃SO₃ (3-Pt); the solid state structure of the isomer bearing the carbonyl ligands pseudo-trans to the bridging phosphide was solved by X-ray diffraction. A remarkable difference was instead found between the reactivity of 1a and 1b towards carbon disulfide or isoprene. In both cases 1b reacts slowly to afford [Pt₂(μ-PBu^t ₂)(μ,η²,η²-CS₂)(PBu^t ₂H)₂]CF₃SO₃ (4-Pt), and [Pt₂(μ-PBu^t ₂)(μ,η²,η²-isoprene) (PBu^t ₂H)₂]CF₃SO₃ (6-Pt), respectively. In the same experimental conditions, 1a is totally inert. A common mechanism, proceeding through the preassociation of the incoming ligand followed by the P---H bond formation between one of the bridging P atoms and the hydride ligand, has been suggested for these reactions.     

Reactivity of cationic carbonyl/phosphine ruthenium(II) compounds

Cis(or trans)-[RuCl₂(CO)₂(PPh₃)₂] react with two and one equivalents of AgBF₄ to give the recently reported [Ru(CO)₂(PPh₃)₂][BF₄]₂·CH₂Cl₂ (1) and novel [RuCl(CO)₂(PPh₃)₂][BF₄] · 1/2 CH₂Cl₂ (2), respectively. Cis-[RuCl₂(CO)₂(PPh₃)₂] also reacts with two equivalents of AgBF₄ in the presence of CO to give [Ru(CO)₃(PPh₃)₂][BF₄]₂ (3). Reactions of 1 and 2 with NaOMe and CO at 1 atm produce the carbomethoxy species [Ru(COOMe)₂(CO)₂(PPh₃)₂] (4) and [RuCl(COOMe)(CO)₂(PPh₃)₂] (5), respectively. Complex 4 can also be formed from the reaction of 3 with NaOMe and CO. Alternatively, 4 is formed from cis-[RuCl₂(CO)₂(PPh₃)₂] with NaOMe and CO at elevated pressure (10 atm); if these reactants are refluxed under 1 atm of CO, [Ru(CO)₃(PPh₃)₂] is the product. The reaction of [RuCl(CO)₃(PPh₃)₂][AlCl₄] with NaOMe provides an alternative route to the preparation of 5, but the product is contaminated with [RuCl₂(CO)₂(PPh₃)₂]. Compounds 1. 2, 4 and 5 have been characterised by IR, ¹H NMR and analysis, whilst the formulation of 3 is proposed from spectroscopic data only. This account also examines the reactivity of [Ru(CO)₂(PPh₃)₂][BF₄]₂ · CH₂Cl₂ with NaBH₄, conc. HCl, KI and, finally, MeCOONa in the presence of CO. The products of these reactions, namely cis-[RuH₂(CO)₂(PPh₃)₂], cis-[RuCl₂(CO)₂(PPh₃)₂], cis-[RuI₂(CO)₂(PPh₃)₂] and [Ru(OOCMe)₂(CO)₂(PPh₃)₂], have been identified by comparison of their spectra with previous literature.