Synthesis and crystal structures of the first germanium-containing alkylidene complexes of molybdenum R3Ge-CHMo(NAr)(OR′)2 (R = Me, Ph) with direct germanium-carbene carbon bond

The novel germanium-containing alkylidene complexes of molybdenum R₃Ge-CHMo(NAr)(OCMe₂CF₃)₂ (Ar = 2,6-i-Pr₂C₆H₃; R = Me, Ph) have been prepared by the reaction of organogermanium vinyl reagents R₃ GeCHCH₂ with known alkylidene compounds Alkyl-CHMo(NAr)(OCMe₂CF₃)₂ (Alkyl = Bu^t, PhMe₂C). The titled compounds were isolated as crystalline solids and characterized by elemental analysis, ¹H NMR, ¹³C NMR spectroscopy and X-ray diffraction studies. The geometry of the Mo atoms in the compounds can be described as a distorted tetrahedron.     

Synthesis and MMA polymerization of chiral ansa-zirconocene ester enolate complexes with C2- and Cs-ligation

A series of chiral ansa-zirconocene ester enolate complexes incorporating C₂- or C_s-symmetric ligands, including neutral rac-(EBI)ZrCl[OC(OⁱPr)CMe₂] (1), rac-(EBI)Zr(OTf)[OC(OⁱPr)CMe₂] (2), rac-(EBI)Zr(OTf)[OC(OMe)C(Me)CH₂C(Me₂)C(OⁱPr)O] (3), [Me₂C(Cp)(Flu)]ZrMe[OC(OⁱPr)CMe₂] (4), and cationic [Me₂C(Cp)(Flu)]Zr⁺(THF)[OC(OⁱPr)CMe₂][MeB(C₆F₅)₃]⁻ (5), have been synthesized. Within the neutral C₂-ligated zirconocene ester enolate series, the chloride derivative 1 is inactive toward any methyl methacrylate (MMA) additions, the methyl derivative rac-(EBI)ZrMe[OC(OⁱPr)CMe₂] adds cleanly only 1 equiv. of MMA, and the triflate derivative 2 can add either 1 equiv. of MMA to form the single-MMA-addition product 3 or multiple equivalents of MMA to form P(MMA). Unlike the C_s-ligated methyl cation [Me₂C(Cp)(Flu)ZrMe]⁺, which is inactive for MMA polymerization under various conditions, the C_s-ligated ester enolate cation 5 is moderately active for polymerization of MMA and N,N-dimethylacrylamide at ambient temperature; the resulting P(MMA) has a high molecular weight of M_n = 388 000 Da but a low syndiotacticity of [rr] = 64%, and the polymerization conforms to a chain-end control mechanism.     

Synthesis and structures of bimetallic silicon-containing imido alkylidene complexes of tungsten (R′O)2(ArN)WCH-SiR2-CHW(NAr)(OR′)2 (R = Me, Ph) and (R′O)2(ArN)WCH-SiMe2SiMe2-CHW(NAr)(OR′)2

Bimetallic alkylidene complexes of tungsten (R′O)₂(ArN)WCH-SiR₂-CHW(NAr)(OR′)₂ (R = Me (1), Ph (2)) and (R′O)₂(ArN)WCH-SiMe₂SiMe₂-CHW(NAr)(OR′)₂ (3) (Ar = ; R′ = CMe₂CF₃) have been prepared by the reactions of divinyl silicon reagents R₂Si(CHCH₂)₂ with known alkylidene compounds R′′-CHMo(NAr)(OR′)₂. (R′′ = Bu^t, PhMe₂C) Complexes 1-3 were structurally characterized. Ring opening metathesis polymerization (ROMP) of cyclooctene using compounds 1-3 as initiators led to the formation of high molecular weight polyoctenamers with predominant trans-units content in the case of 1 and 3 and predominant cis-units content in the case of 2.     

Formation of multifunctional ligands by nucleophilic addition of alcohols and thiols to the alkyne groups in compound C5H5FeC5H4CCSCCH: Reactivity studies

The multifunctional ligands [(Z)-FcCCSC(H)C(H)XR] [X = O, R = Me (2a); X = O, R = Et (2b); X = S, R = Ph (3); X = S, R = C₆F₅ (5)] and [(Z,Z)-Fc(SR)CC(H)SC(H)C(H)SR] [R = Ph (4), C₆F₅ (6)] have been prepared through hydroalkoxylation and hydrothiolation processes of the alkyne groups in the compound FcCCSCCH 1. Reactions between compound 3 and the carbonyl metals Co₂(CO)₈, Os₃(CO)₁₀(NCMe)₂ and Fe₂(CO)₉ have allowed the synthesis of the polynuclear compounds [(Z)-{Co₂(CO)₆}(μ-η²-FcCCSC(H)C(H)SPh)] 9, [(Z)-Os₃(CO)₉(μ-CO){μ₃-η²-FcCCSC(H)C(H)(SPh)}] 10 and [(Z)-{Fe₃(CO)₉}[μ₃,η³-(CCS)-FcCCSC(H)C(H)(SPh)] 11. All the compounds have been characterized by elemental analysis, ¹H and ¹³C{¹H} NMR spectroscopy, mass spectrometry and the crystal structure of compounds [(Z)-FcCCSC(H)C(H)OMe] 2a and [{Co₂(CO)₆}₂(μ-η²:η²-FcCCSCCSiMe₃)] 7 have been solved by X ray diffraction analysis.     

Reaction of trifluoromethylated β-alkoxyenones with tris(trimethylsilyl) phosphite: A temperature influence on regioselectivity

The interaction of tris(trimethylsilyl) phosphite (TMSO)₃P and E-trifluoromethyl-β-alkoxyenones CF₃C(O)CHCHOEt and CF₃C(O)CHC(OMe)Me yielded mixtures of E-1,2- and Z-1,4-adducts, CF₃C(OTMS)[P(O)(OTMS)₂]CCH(OAlk)R 2 and CF₃(OTMS)CCHCR(OAlk)[P(O)(OTMS)₂] 3 where R and Alk = H and Me, or both Me. Conversion of these 1,2-adducts to 1,4-isomers was effected by increased temperature or by exposure to more tris(trimethylsilyl) phosphite. Acid hydrolysis of 2b (R and Alk = Me) gave ketophosphonic acid CF₃C(OH)[P(O)(OH)₂]CH₂COMe in 88% yield, whereas hydrolysis of 2a (R = H and Alk = Et) with KOH in methanol gave CF₃C(OH)[P(O)(OK)₂]CHCHOEt in 37% yield. Acid hydrolysis of 3a (R = H and Alk = Et) and 3b (R and Alk = Me) gave phosphonic acid CF₃C(OH)₂CHCHP(O)(OH)₂ in 82% yield and trifluoromethylated 1,2λ⁵σ⁴-oxaphosphol-3-en.     

SPh functionalized bridging-vinyliminium diiron and diruthenium complexes

The SPh functionalized vinyliminium complexes [Fe₂{μ-η¹:η³-C_γ(R′)C_β(SPh)C_αN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] [R = Xyl, R′ = Me, 2a; R = Me, R′ = Me, 2b; R = 4-C₆H₄OMe, R′ = Me, 2c; R = Xyl, R′ = CH₂OH, 2d; R = Me, R′ = CH₂OH, 2e; Xyl = 2,6-Me₂C₆H₃] are generated in high yields by treatment of the corresponding vinyliminium complexes [Fe₂{μ-η¹:η³-C_γ(R′)C_β(H)C_αN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (1a-e) with NaH in the presence of PhSSPh. Likewise, the diruthenium complex [Ru₂{μ-η¹:η³-C_γ(Me)C_β(SPh)C_αN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (2f) was obtained from the corresponding vinyliminium complex [Ru₂{μ-η¹:η³-C_γ(Me)C_β(H)C_αN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂] (1f). The synthesis of 2c is accompanied by the formation, in comparable amounts, of the aminocarbyne complex [Fe₂{μ-CN(Me)(4-C₆H₄OMe)}(SPh)(μ-CO)(CO)(Cp)₂] (3).The molecular structures of 2d, 2e and 3 have been determined by X-ray diffraction studies.     

Chemistry of vinylidene complexes. XX. Intramolecular carbonylation of vinylidene on the MnFe center: Spectroscopic and structural study. X-ray structure of the new trimethylenemethane type MnFe complex

Reactions of Fe₂(CO)₉ with Cp(CO)₂MnCCHPh (1) and Cp(CO)(PPh₃)MnCCHPh (3) gave the heterometallic trimethylenemethane complexes η⁴-{C[Mn(CO)₂Cp](CO)CHPh}Fe(CO)₃ (2) and η⁴-{C[Mn(CO)(PPh₃)Cp](CO)CHPh}Fe(CO)₃ (4), respectively. The formation of the benzylideneketene [PhHCCCO] fragment included in complexes 2 and 4 occurs via intramolecular coupling of the carbonyl and vinylidene ligands. The structures of 3 and 4 were determined by single crystal XRD methods. The influence of the nature of the L ligands at the Mn atom on the structural and spectroscopic characteristics of η⁴-{C[Mn(CO)(L)Cp](CO)CHPh}Fe(CO)₃ (L = CO (2), PPh₃ (4)) is considered. According to the VT ¹H and ¹³C NMR spectra, complex 2 reversibly transforms in solution into μ-η¹:η¹-vinylidene isomer Cp(CO)₂MnFe(μ-CCHPh)(CO)₄ (2a), whereas complex 4 containing the PPh₃ ligand is not able to a similar transformation.     

New chiral phosphoramidite allenylidene complexes of ruthenium obtained with chirality transfer

The synthesis and structural characterization of the first ruthenium phosphoramidite allenylidene complexes that are chiral at the metal are described. The precursor complex [RuCl(Ind)(PPh₃)₂] (Ind = indenyl anion) was reacted with 1 equiv of different chiral phosphoramidite ligands L to give complexes of the general formula [RuCl(Ind)(PPh₃)L]. These complexes are stereogenic at the metal and at the ligand L. One of these complexes was obtained in diastereomeric purity, and was subsequently converted to allenylidene complexes of the general formula [RuCCCR′R(Ind)(PPh₃)L]⁺PF₆ (R = R′ = Ph; R = Ph, R′ = Me) in diastereomeric purity. As shown by X-ray, the chiral information is completely transferred from the precursor complex to the allenylidenes, which is of importance for potential catalytic applications.     

Additions and intramolecular migrations of nucleophiles in cationic diruthenium μ-allenyl complexes

The diruthenium μ-allenyl complex [Ru₂(CO)(NCMe)(μ-CO){μ-η¹:η²-C(H)CC(Me)(Ph)}(Cp)₂][BF₄], 3b, reacts with halide anions to yield the neutral derivatives [Ru₂(CO)₂(X){μ-η¹:η²-C(H)CC(Me)(Ph)}(Cp)₂] [X = Cl, 4b; X = Br, 4c; X = I, 4d]. Complex 4b undergoes isomerization to the unprecedented bridging vinyl-chlorocarbene species [Ru₂(CO)(μ-CO){μ-η¹:η³- C(Cl)C(H)C(Me)(Ph)}(Cp)₂], 10, upon filtration of a CH₂Cl₂ solution through an alumina column.Complex 3b reacts with an excess of NaBH₄ to give five products: the allene complex [Ru₂(CO)₂{μ-η²:η²- CH₂CC(Me)(Ph)}(Cp)₂], 5; the hydride species trans-[Ru₂(CO)₂(μ-H){μ-η¹:η²-CHCC(Me)(Ph)}(Cp)₂], 6, and cis-[Ru₂(CO)₂(μ-H){μ-η¹:η²-CHCC(Me)(Ph)}(Cp)₂], 8; the vinyl-alkylidene [Ru₂(CO)(μ-CO){μ-η¹:η³- C(H)C(H)C(Me)(Ph)}(Cp)₂], 9; and the cluster [Ru₃(CO)₃(μ-H)₃(Cp)₃], 7.Studies on the thermal stabilities of 5, 6, 8 and 9 have suggested a plausible mechanism for the formation of these complexes and for the synthesis of 10.     

A promising new catalyst family for enantioselective cycloadditions involving allenes and imines: chiral phosphines with transition metal-CH2-P: linkages

The racemic rhenium-containing phosphine (η⁵-C₅H₅)Re(NO)(PPh₃)(CH₂PPh₃) (3) catalyzes the [3+2] cycloaddition of H₂CCCHCO₂Et and N-tosyl imines ArCHNTs in C₆H₆ (RT, 1 d, 20 mol %) to give 2-aryl-3-carbethoxy-3-pyrrolines (Arp-C₆H₄X (X = H, NO₂, OMe, Me, Cl, Br), 2-furyl; 95-84% isolated). Similar reactions with enantiopure (S)-3 are conducted in C₆H₅Cl at −30 °C (8 d) to maximize enantioselectivities (60-51% ee; 93-90% isolated).     

Reactions of cyano(alkynyl)ethenes with some alkynyl- and diynyl-ruthenium complexes

Reactions of Ru(CCPh)(PPh₃)₂Cp with (NC)₂CCR¹R² (R¹ = H, R² = CCSiPrⁱ₃8; R¹ = R² = CCPh 9) have given η³-butadienyl complexes Ru{η³-C[C(CN)₂]CPhCR¹R²}(PPh₃)Cp (11, 12), respectively, by formal [2 + 2]-cycloaddition of the alkynyl and alkene, followed by ring-opening of the resulting cyclobutenyl (not detected) and displacement of a PPh₃ ligand. Deprotection (tbaf) of 11 and subsequent reactions with RuCl(dppe)Cp and AuCl(PPh₃) afforded binuclear derivatives Ru{η³-C[C(CN)₂]CPhCHCC[ML_n]}(PPh₃)Cp [ML_n = Ru(dppe)Cp 19, Au(PPh₃) 20]. Reactions between 8 and Ru(CCCCR)(PP)Cp [PP = (PPh₃)₂, R = Ph, SiMe₃, SiPrⁱ₃; PP = dppe, R = Ph] gave η¹-dienynyl complexes Ru{CCC[C(CN)₂]CRCH[CC(SiPrⁱ₃)]}(PP)Cp (15-18), respectively, in reactions not involving phosphine ligand displacement. The phthalodinitrile C₆H(CCSiMe₃)(CN)₂(NH₂)(SiMe₃) 10 was obtained serendipitously from (Me₃SiCC)₂CO and CH₂(CN)₂, as shown by an XRD structure determination. The XRD structures of precursor 7 and adducts 11, 12 and 17 are also reported.     

Effect of substituents on the molybdenum mediated carbonylation and methoxycarbonylation of dihaloalkynes

Dihaloalkynes of the type YCH(R)CCCH(R)Y (Y = Cl, Br, I; R = H or Me) or YCMe₂CCCMe₂Y were prepared from their diol precursors and reacted with [Mo(CO)₃(phen)Y]⁻ (phen = 1,10-phenanthroline) in chlorinated solvent, methanol or water. Formation and stability of substituted products of the type [Mo(CO)₂(η³-CH(R)C(COX)CCH(R))(phen)Y] (X = Y or X = OMe) were found to be dependent upon the nature of the halogen and degree of alkyl substitution of the alkyne. Reactions carried out in mixtures of methanol and ethers gave an alternative double addition product of the type [Mo(CO)₂(η³-CH(R)C(CO₂Me)CC(OMe)(CH₂R))(phen)Y] for R = H, Y = Cl only.     

Titanium and zirconium ketimide complexes: synthesis and ethylene polymerisation catalysis

The syntheses of ketimide titanium complexes of the type Ti(NC^tBu₂)₃X (X = Cl, Cp, Ind), Ti(NC^tBu₂)₄ and the zirconium complex CpZr(NC^tBu₂)₂Cl are described. When activated by MAO, all compounds are ethylene polymerisation catalysts. In the conditions studied, the most active catalyst is CpZr(NC^tBu₂)₂Cl, with an activity of 2.7 × 10⁵ kg/(molZr [E] h). Titanium complexes are less active by about two orders of magnitude. The polyethylene produced is linear, as determined by NMR spectroscopy. Molecular structures of Ti(NC^tBu₂)₃X (X = Cl, Cp, Ind) and Ti(NC^tBu₂)₄ were determined by X-ray single crystal diffraction.     

Alkyne activation by half-sandwich ruthenium(II) complexes bearing the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane (PTA)

Complex [RuCl{κ³(N,N,N)-Tp}(PPh₃)(PTA)] (κ³(N,N,N)-Tp = hydridotris(pyrazolyl)borate) containing the water-soluble phosphane 1,3,5-triaza-7-phosphatricyclo[3.3.1.1^3,7]decane (PTA) reacts with terminal alkynes producing to the corresponding neutral alkynyl complexes [Ru(CCR){κ³(N,N,N)-Tp}(PPh₃)(PTA)] (R = Ph (1a), ⁿBu (1b), 1-cyclopentenyl (1c), p-methoxyphenyl (1d), 6-methoxynaft-2-yl (1e)). When halide is extracted from complex [RuCl{κ³(N,N,N)-Tp}(PPh₃)(PTA)] followed by treatment with propargyl alcohols, the corresponding allenylidene complexes [Ru{κ³(N,N,N)-Tp}(PPh₃)(PTA)(CCCPh₂)][X] (X = PF₆ (2a), CF₃SO₃ (2b)) and [Ru{κ³(N,N,N)-Tp}(PPh₃)(PTA)(CCCC₁₂H₈)][PF₆] (3) result. Electrophilic attack on the complexes thus obtained leads chemoselectively to the alkynyl complexes [Ru(CCR){κ³(N,N,N)-Tp}(PPh₃)(1-CH₃-PTA)][CF₃SO₃] (R = Ph (4a), ⁿBu (4b), and 1-cyclopentenyl (4c)) and to the dicationic allenylidene complexes [Ru{κ³(N,N,N)-Tp}(PPh₃)(1-H-PTA)(CCCC₁₂H₈)][PF₆]₂ (5) and [Ru{κ³(N,N,N)-Tp}(PPh₃)(1-CH₃-PTA)(CCCPh₂)][CF₃SO₃]₂ (6).     

Synthesis, characterization and reactivity of the molybdenum(VI) complex [MoCl(NAr)2(CH2CMe2Ph)] (Ar=2,6-Pr2C6H3)

The compounds [MoCl(NAr)₂R] (R=CH₂CMe₂Ph (1) or CH₂CMe₃(2); Ar=2,6-Prⁱ₂C₆H₃) have been prepared from [MoCl₂(NAr)₂(dme)] (dme=1,2-dimethoxyethane) and one equivalent of the respective Grignard reagent RMgCl in diethyl ether. Similarly, the mixed-imido complex [MoCl₂(NAr)(NBu^t)(dme)] affords [MoCl(NAr)(NBu^t)(CH₂CMe₂Ph)] (3). Chloride substitution reactions of 1 with the appropriate lithium reagents afford the compounds [MoCp(NAr)₂(CH₂CMe₂Ph)] (4) (Cp=cyclopentadienyl), [MoInd(NAr)₂(CH₂CMe₂Ph)] (5) (Ind=Indenyl), [Mo(OBu^t)(NAr)₂(CH₂CMe ₂Ph)] (6), [MoMe(NAr)₂(CH₂CMe₂Ph)] (7), [MoMe(PMe₃)(NAr)₂(CH₂CMe ₂Ph)] (8) (formed in the presence of PMe₃) and [Mo(NHAr)(NAr)₂(CH₂CMe₂P h)](9). In the latter case, a by-product {[Mo(NAr)₂(CH₂CMe₂Ph) ]₂(μ-O)}(10) has also been isolated. The crystal structures of 1, 4, 5 and 10 have been determined. All possess distorted tetrahedral metal centres with cis near-linear arylimido ligands; in each case (except 5, for which the evidence is unclear) there are α-agostic interactions present.     

Novel (η-arene)-ruthenium(II) complexes containing bis(iminophosphorano)methanide and methandiide ligands

The novel bis(iminophosphorano)methanes CH₂[P{NP(S)(OR)₂}Ph₂]₂ (R = Ph (1a), Et (1b)) have been obtained by oxydation of dppm with the corresponding thiophosphorylated azides (RO)₂P(S)N₃. Deprotonation of 1a,b with KH generates the methanide species KCH[P{NP(S)(OR)₂}Ph₂]₂ (R = Ph (2a), Et (2b)). The ruthenium(II) dimer [{Ru(η⁶-p-cymene)(μ-Cl)Cl}₂] reacts with 2a,b to afford the cationic complexes [Ru(η⁶-p-cymene)(κ³-C,N,S-CH[P{NP(S)(OR)₂}Ph₂]₂)]⁺ (R = Ph (3a), Et (3b)), via selective κ³-C,N,S-coordination of the bis(iminophosphorano)methanide anions to ruthenium. The structure of [Ru(η⁶-p-cymene)(κ³-C,N,S-CH[P{NP(S)(OEt)₂}Ph₂]₂)][PF₆] (3b) has been confirmed by single-crystal X-ray crystallography. Deprotonation of complexes 3a,b with NaH leads to the neutral carbene derivatives [Ru(η⁶-p-cymene)(κ²-C,N-C[P{NP(S)(OR)₂}Ph₂]₂)] (R = Ph (4a), Et (4b)).     

Addition of benzenethiol to terminal alkynes catalyzed by hydrotris(3,5-dimethylpyrazolyl)borate-Rh(III) bis(thiolate) complex: Mechanistic studies with characterization of the key intermediate

The Rh(III)-thiolate complex [Tp^∗Rh(SPh)₂(MeCN)] (2; Tp^∗ = hydrotris(3,5-dimethylpyrazolyl)borate) readily undergoes substitution of MeCN by XyNC (Xy = 2,6-dimethylphenyl) to give the isocyanide complex [Tp^∗Rh(SPh)₂(XyNC)] (3), whereas reaction of 2 with terminal alkynes results in the formation of the rhodathiacyclobutene complex [Tp^∗Rh(SPh){η²-CHCR(SPh)}] (4; R = aryl, alkyl). Molecular structures of 3 and 4 (R = CH₂Ph) have been determined by single crystal X-ray diffraction. Complex 2 as well as [Tp^∗Rh(cyclooctene)(MeCN)] have been found to catalyze regioselective addition of benzenethiol to terminal alkynes RCCH at 50 °C to give R(PhS)CCH₂ in moderate to high yields. The above products are selectively formed when R = CH₂Ph and n-C₆H₁₃, while cis-RCHCHSPh and RC(SPh)₂CH₃ are also obtained as by-products when R = p-MeOC₆H₄. Catalytic cycle involving 2 and 4 is proposed based on the mechanistic studies using NMR measurement.     

Proton reduction catalysis by manganese vinylidene and allenylidene complexes

The present paper reports the unprecedented observation of a catalytic electrochemical proton reduction based on metallocumulene complexes. Manganese phenylvinylidene (η⁵-C₅H₅)(CO)(PPh₃)MnCC(H)Ph (1) and diphenylallenylidene (η⁵-C₅H₅)(CO)₂MnCCCPh₂ (3) are shown to catalyze the reduction of protons from HBF₄ into dihydrogen in CH₂Cl₂ or CH₃CN media at −1.60 and −0.84 V (in CH₃CN) vs. Fc, respectively. The working potential for 3 (−0.84 V vs. Fc in CH₃CN) is the lowest reported to date for protonic acids reduction in non-aqueous media. The similar catalytic cycles disclosed here include the protonation of 1, 3 into the carbyne cations [(η⁵-C₅H₅)(CO)(PPh₃)MnC-CH₂Ph]BF₄ ([2]BF₄), [(η⁵-C₅H₅)(CO)₂MnC-CHCPh₂]BF₄ ([4]BF₄) followed by their reduction to the corresponding 19-electron radicals 2, 4, respectively. Both carbyne radicals undergo a rapid homolytic cleavage of the C_β-H bond generating an H-radical producing molecular hydrogen with concomitant recovery of the neutral metallocumulenes thereby completing a catalytic cycle.