Unexpected formation of the novel mixed mu-oxo, mu-sulfido, bis(mu-thiolato) compound [Mo(IV)(2)(Cp-2(mu-O)(mu-S)(mu-SMe)(2)]

cited By 7International audienceA novel example of C-S bond cleavage in a dimolybdenum derivative leads to the formation of the quadruply bridged compound [Mo(IV)2Cp2(μ-O)(μ-S)(μ-SMe)2]. This μ-oxo species is formed by reaction of the chloro-bridged complex [Mo(III)2Cp2(μ-Cl)(μ-SMe)3] with PhCCLi and subsequent hydration at the dimolybdenum site. The Mo-Mo bond length of 2.4900(3)Å in [Mo2Cp2(μ-O)(μ-S)(μ-SMe)2] is unusually short. © 2001 Elsevier Science B.V

cis- and trans-bis(1-phenyl-2,3,4,5-tetramethylphosphole)tetracarbonylmolybdenum(0), [Mo(CO)(4)(tmpPh)(2)]. Syntheses and structures

cited By 7International audience1-Phenyl-2,3,4,5-tetramethylphosphole reacts with [Mo(CO)6] to give the mono- and bis(phosphole) complexes [Mo(CO)5L] and cis- and trans-[Mo(CO)4L2], where L=C4Me4PPh (tmpPh). The new complexes have been characterised by spectroscopic methods, supplemented by single-crystal X-ray analyses in the case of the bis(phosphole) isomers. The isomeric bis-tmpPh complexes show little evidence of the overcrowding which is thought to lengthen bonds and distort the metal coordination in the corresponding bis-PPh3 and bis-PCy3 isomers. The structural basis for the greater stability of the trans isomers is briefly considered: the cis→trans isomerisation typically involves little change in the mean Mo-CO distance, whereas there is a marked shortening of the Mo-P bonds. © 2001 Elsevier Science B.V

Reaction of BH4- with {Mo2Cp2(mu-SMe)(n)} species to give tetrahydroborato, hydrido or dimetallaborane compounds: control of product by ancillary ligands

cited By 28International audienceThe reaction of mono- or dichloro-dimolybdenum(m) complexes [Mo 2Cp2(μ-SMe)2(μ-Cl)(μ-Y)] (Cp=η5-C5H5; 1, Y = SMe; 2, Y = PPh 2; 3, Y = Cl) with NaBH4, at room temperature gave in high yields tetrahydroborato (8), hydrido (9) or metallaborane (12) complexes depending on the ancillary ligands. The correct formulation of derivatives 8 and 12 has been unambigously determined by X-ray diffraction methods. That of the hydrido compound 9 has been established in solution by NMR analysis and confirmed by an X-ray study of the μ-azavinylidene derivative [Mo 2Cp2(μ-SMe)2(μ-PPh2)(μ-N= CHMe)] (10) obtained from the insertion of acetonitrile into the Mo-H bond of 9. Reaction of NaBH4, with nitrile derivatives, [Mo2Cp 2(μ-SMe)4-n(CH3CN)2n] n+ (5, n= 1; 6 =2), afforded the tetrahydroborato compound 8, together with a μ-azavinylidene species [Mo2Cp2(μ- SMe)3(μ-N=CHMe)] (14), when n= 1, and the metallaborane complex 12, together with a mixed borohydrato-azavinylidene derivative [Mo 2Cp2(μ-SMe)2(μ-BH4)(μ-N= CHMe)] (13), when n=2. The molecular structures of these complexes have been confirmed by X-ray analysis. Preparations of some of the starting complexes (3 and 4) are also described, as are the molecular structures of the precursors [Mo2Cp2(μ-SMe)2(μ-X)-(μ-Y)] (1, X/Y = Cl/SMe; 2, X/Y = Cl/PPh2; 4, X/Y = SMe/PPh2)

mu-alkylidyne and mu-alkylidene complexes from a bridging side-on vinylidene sulfur-rich dimolybdenum precursor

International audienceThe reaction of the μ-vinylidene sulfur-rich dimolybdenum complexes with μ-alkyldyne derivatives was investigated. The reaction resulted in good yield, and when treated with a HBF4·Et2O based complex it readily converted into μ-alkyldene species. The α-agostic interactions in the μ-alkyldene complexes were revealed through NMR spectroscopy

Activation and functionalization of vinylic C-F bonds by transition metal compounds: The factors determining reactions between nucleophiles and a (perfluorovinyl)diiron(I) complex; Syntheses of diiron derivatives containing new C-N, C-S, C-H and C-O bonds

International audienceThe reactions between alcohols ROH (R = Me, Et) and RR(OH)2 (RR = CH2-CH2) and the [perfluoro(sulfanyl)vinyl]- diiron complex [_Fe(CO)3₂_μ-C(SMe) (CF3)CβCαF2_] (1) in THF at room temperature involve substitution at the Cα atom to give new (alkoxymethylene)thiaferracyclobutadiene compounds [_Fe(CO)3₂_μ-S(Me)C (CF3)CβCα(OR)2_] [R = Me (2a), Et (2b); RR = CH2CH2 (2c)]. Treatment of 1 with aniline and (methoxycarbonyl)hydrazine, bases of intermediate strength according to Pearson, produces α,β-substituted thiaferracyclopentadiene [_Fe(CO)3₂_μ-S(Me)C (CF3)Cβ(NHR)Cα-(NHR)_] [R = Ph (5a), NHC(O)OMe (5b)] complexes. It is suggested that these compounds form through initial nucleophilic attack at Cα to give the zwitterionic intermediate [_Fe(CO)3₂_μ-S(Me)C (CF3)CC(NRH)2_] (f). Thermally induced C-F bond activation is a feature of these reactions. When 1 reacts with thioamides containing three "hard" competitive primary and secondary amine functions and one "soft" thione function, the nucleophile first attacks at Cα through a secondary amine and, in a second step, at Cβ through the thiol function to give α,β adducts [_Fe(CO)3₂_μ-S(Me)C (CF3)CβSC(=NR2)N (R1)Cα(Cβ-Cα)] [R1 = NH2, R2 = CH3 (6a); R1 = CH3, R2 = H (6b); R1 = R2 = CH3 (6c)l possessing novel iminothiazolidine systems fused to the five-membered metallacyclic ring. Treatment of 1 with acetylhydrazine, which has three "hard" nucleophilic functions, results in the formation of the compound [_Fe(CO)3₂_μ-S(Me)C (CF3)C(H)C(10)NNC(Me)O(C(10)-O)_] (7a), in which an oxadiazole function is fused to the thiaazaferracyclohexene ring. The position of the fluorine substituent on the CαCβCγ(CF3)S(Me) ring of ferracyclopentadiene complexes has been found to be the essential factor determining the specific activation of the C-F bond. A single fluoro substituent attached to the β-carbon atom of the chain can be activated by nucleophiles to give α,β adducts [_Fe(CO)3₂_μ-S(Me)C (CF3)Cβ(X)Cα(NRR′)_] [X = OR″, R = R′ = R″ = Me (3a); X = OR″, R = R″ = Me, R″ = C(O)NMe2 (3b); X = SR″ (4)]. In contrast, complexes in which a single fluorine atom is linked to the α-carbon atom do not undergo C-F bond cleavage reactions. X-ray structures of compounds 2a, 3b, 5a, 5b, 6a and 7a are reported

Controlled nucleophilic activation of different sites in [Mo2Cp2L2(mu-SMe)(2)(mu-L ')](+) cations (L = (BuNC)-N-t, xylNC, CO; L '= SMe or PPh2)

cited By 15International audienceThe thiolato-bridged binuclear molybdenum complexes [Mo2Cp 2L2(μ-SMe)2(μ-L′)]Y (Cp = η5-C5H5; L′ = SMe, L = Bu tNC (1a), xylNC (1b) or CO (3); L′ = PPh2, L = ButNC (16); Y = BF4, Cl) react with the anionic reagents NaBH4, NaBD4, LiR (R = Me, Bun), R′MgCl (R′ = Me, Pri, Bun or Ph). The products are unsubstituted (5, 7) or substituted (8-12) η4-cyclopentadiene derivatives, [Mo2(η5-C5H 5)(η4-C5H5R)L 2(μ-SMe)3] (L = xylNC, CO), or μ-formimidoyl dinuclear products, [Mo2Cp2L2(μ-SMe) 2(μ-L′)(μ-CHNR)] (L′ = SMe, L = ButNC (4) or xylNC (6); L′ = PPh2, L = ButNC (17)). Since the reduced dinuclear species [Mo2Cp2(CO) 2(μ-SMe)2] and the related oxo-compound [Mo 2Cp2(CO)(O)(μ-SMe)2] are sometimes isolated as minor products, the anionic reagent can play a secondary role as a reductant in these reactions in addition to its main role as a nucleophile. The electronic properties of the donor carbon atoms of the cyclopentadienyl rings and of the terminal ligands L, together with the nature of the anionic reagent, are the dominant factors controlling selective formation of 4-12 and 17. Tetrafluoroboric acid reacts with the substituted cyclopentadiene derivatives 9, 11 and 12 to form new functionalised cyclopentadienyl derivatives, [Mo 2(η5-C5H5)(η5- C5H4R)(CO)2(μ-SMe)3](BF 4) (R = Me (13), Bun (14) or Ph (15)). New complexes have been characterised by spectroscopic and chemical methods, supplemented for 5, 6 and 12 by X-ray diffraction studies at 100 K. © 2005 Elsevier B.V. All rights reserved

Transformations of hydrazines RNHNH2 (R = Me, Ph) at a sulfur-rich bimetallic site: diazene-isodiazene/hydrazido(2-) interconversions

[Cp*GaCl2] (Cp* = 1-C5Me5) reacts with K[Co(CO)4] with elimination of KCp* and KCl to form the novel ionic complexes [K(toluene)2][Ga{Co2(CO)6(-CO)}2] (1) and K[GaCl{Co2(CO)6(-CO)}{Co(CO)4}] (2), where the gallium atoms possess the coordination number four. The reaction of [{Co(CO)4}2GaCl(THF)] with LiCp* leads to the ionic product [Li(THF)][Ga{Co2(CO)6(-CO)}2] (3). The [Ga{Co2(CO)6(-CO)}2]- anions of 1 and 3 represent the first homoleptic spirocyclic coordination mode of gallium. The reaction of GaCl3 with Na2[Fe(CO)4] leads to the ionic compound [Na(OEt2)2][Fe(CO)4(GaCl3)2] (4). Complexes 1, 2, 3 and 4 were characterised by X-ray structure analysis and IR spectroscopy. Additionally, ESI mass spectra of 1 were recorded at different cone voltages, where the molecular ion peak of the anion [Ga{Co2(CO)6(-CO)}2]- as well as the peaks resulting from sequential loss of CO ligands until the formation of the naked [Co4Ga]- cluster are observed. The ionic complexes 1, 2, 3 and 4 form polymeric networks through coordination of their cations. In 2 a three-dimensional polymeric network is formed by coordination of the Co3Ga units and their K counterions, whereas in 1 the K ions are additionally coordinated by toluene molecules to form dimeric macrocyclic motifs by coordination of two of the anionic Co4Ga units. In 3 a zigzag chain is formed by coordination of the Co4Ga units through their Li cations. In the crystal packing of complex 4 the FeGa2 moieties form zigzag chains, coordinating through their Na counterions

Electrochemical studies of complexes with oxo- or hydroxo-bridged {Mo-2(mu-SMe)(3)}(+) centers: Cleavage of the oxygen bridge and generation of substrate-binding sites

cited By 9International audienceThe reduction of [Mo2(Cp)2(μ-SMe) 3(μ-O)]+ (1+) has been investigated by cyclic voltammetry and controlled-potential electrolysis in THF- and MeCN/NBu4PF6 without added acid or in the presence of various acids HX (HX: HTsO, CF3CO2H, HBF4). Reduction in the presence of acid follows an ECrevE mechanism in which the intermediate chemical step is an acid-base equilibrium between 1 and [Mo2(Cp)2(μ-SMe)3(μ-OH)]+ (2+). This electrochemical process is followed by protonation of the neutral μ-hydroxo complex 2 to afford different products which depend both on the solvent (THF or MeCN) and on the nature of the acid. Controlled-potential electrolysis of 1+ in the presence of HX (2 equiv.) leads to the generation of binding sites and finally gives products identical to those obtained from protonation of 2 by HX. The complex [Mo2(Cp) 2(μ-SMe)3(μ-η1,η1- OCOCF3)] (3) which can be obtained either by protonation of 2 by CF3CO2H or by reduction of 1+ in the presence of CF3CO2H, has been characterized crystallographically. In the presence of HBF4 protonation of 1+ gives 2 2+. The reactivity of 2+ and of the complexes [Mo 2(Cp)2(μ-SMe)3(H2O)(TsO)] (4) and [Mo2(cp)2(μ-SMe)3(H2O)L] + (L = H2O or THF) (6+), all of which contain a terminal aqua ligand, has also been investigated. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004

Incorporation of alkyne and vinylidene ligands into tetrazolate groups at a sulfur-rich dimolybdenum site using sodium azide

cited By 9International audienceTreatment of either the μ-alkyne complex [Mo2Cp 2(μ-SMe)3(μ-PhCCH)](BF4) (1) or the μ-vinylidene derivatives [Mo2Cp2(μ-SMe) 3(μ-η1:η2-(CCHR)](BF4) (2) (R=Ph, Tol, nPr, C(CH3)=CH2) with NaN3 in ethanol at room temperature readily afforded μ-tetrazolate carbene complexes [Mo2Cp2(μ-SMe)3)μ-η 1(C):η1(N)-N4CCR)] (R=Ph (4a), Tol (4b), nPr (4c), C(CH3)=CH2 (4d)). A mechanism which accounts for the formation of 4 by intramolecular 1,3-dipolar cycloaddition of metal-coordinated azide ligands to metal-coordinated nitriles is discussed. The structure of complex 4a has been determined by single X-ray diffraction analysis. © 2003 Elsevier Science B.V. All rights reserved