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International audience; Reaction of the bis(nitrile) complex [Mo2Cp2(μ-SMe)3(NCMe)2](BF4) (1) with dimethylpropargylic alcohol, HCtriple bond; length of mdashCCMe2(OH), at room temperature in dichloromethane produced good yields of the μ-alkynol species [Mo2Cp2(μ-SMe)3{μ-CHCCMe2(OH)}](BF4) (2a) through replacement of the two acetonitrile ligands in 1 by the alkynol. The NMR spectra of 2a indicate a μ-η1:η1 coordination mode for the alkyne which is thereby incorporated into a dimetallacyclobutene ring like that found here by X-ray diffraction (XRD) analysis of the related complex [Mo2Cp2(μ-SMe)3(μ-η1:η1-CHCCO2Me)](BPh4) (2b). When 2a was stirred with Et3N at room temperature in dichloromethane, deprotonation gave high yields of the μ-3-hydroxyalkynyl derivative [Mo2Cp2(μ-SMe)3{μ-η1:η2-CCCMe2(OH)}] (3), together with small amounts of the already-known vinylacetylide [Mo2Cp2(μ-SMe)3{μ-η1:η2-CCC(Me)CH2}] (4) resulting from dehydration of 3. Treatment of 3 with 1 equiv. of HBF4 · OEt2 in diethyl ether at room temperature gave the 3-hydroxyvinylidene derivative [Mo2Cp2(μ-SMe)3{μ-η1:η2-CCHCMe2(OH)}](BF4) (5) as the major product, together with other minor products [Mo2Cp2(μ-SMe)3{μ-η1:η2-CCHC(Me)CH2}](BF4) (6), [Mo2Cp2(μ-SMe)3(μ-η1:η2-CCCMe2)](BF4) (7), [Mo2Cp2(μ-SMe)3(μ-η1:η2-CCH2)](BF4) (8), [Mo2Cp2(μ-SMe)3{μ-η1:η2-CCH(CHMe2)}](BF4) (9) and [Mo2Cp2(μ-SMe)3(μ-O)](BF4) (10). The vinylidene (6) and allenylidene (7) species resulted from dehydration of the 3-hydroxyvinylidene complex 5 whereas the vinylidene derivative 8 was formed by deketonisation of 5. When 3 reacted with a large excess of HBF4 · OEt2 in dichloromethane, the 3-isopropylvinylidene complex 9 was obtained nearly quantatively via a Hradical dot radical process. When left for several days CD2Cl2 solutions of 5 afforded mainly the vinylidene species 8 by deketonisation and the side-oxoproduct [Mo2Cp2(μ-SMe)3(μ-O)](BF4) (10) by hydrolysis or reaction with oxygen. Addition of nucleophiles (H−, OMe−, OH−, SMe−) to the allenylidene complex [Mo2Cp2(μ-SMe)3(μ-η1:η2-CCCPh2)](BF4) (11) resulted in the formation of the corresponding μ-acetylide derivatives [Mo2Cp2(μ-SMe)3(μ-η1:η2-CCCRPh2)] [R = H (12), OMe (16a), OH (17), SMe (16b)], which by further reaction with tetrafluoroboric acid afforded either the vinylidene species [Mo2Cp2(μ-SMe)3{μ-η1:η2-CCH(CRPh2)}](BF4) when R = H (13), or the starting complex 11 when R is a leaving group (OMe). Reaction of 13 with Na(BH4) gave the μ-alkylidyne complex [Mo2Cp2(μ-SMe)3(μ-η1-CCH2CPh2H)] (14) by nucleophilic attack of H− at the Cβ carbon atom of the vinylidene chain. Proton addition at Cα in 14 led to the formation of a μ-vinylidene compound 15 containing an agostic C–H bond. New complexes have been characterised by elemental analyses and spectroscopic methods, supplemented for 2b and 3 by X-ray diffraction studies.

The complexes [Fe2(CO)6{μ-SCH2N(R) CH2S}] (R = CH2CH2OCH3, 1a; R = iPr, 1b) and [Fe2(CO)6(μ-pdt)] 2 (pdt = S(CH2)3S) are structural analogues of the [2Fe] H subsite of [FeFe]H2ases. Electrochemical investigation of 1 and 2 in MeCN-[NBu4][PF6] under Ar and under CO has demonstrated that the reduction can be resolved into two one-electron transfer steps by using fast scan cyclic voltammetry. At slow scan rates the reduction of 1 tends towards a two-electron process owing to the fast disproportionation of the anion, while the two-electron reduction of 2 is clearly favoured in the presence of CO. Substitution of a CO ligand in 2 by a N-heterocyclic carbene results in the destabilisation of the anion. Thus, in MeCN-, thf- or CH 2Cl2-[NBu4][PF6], the electrochemical reduction of Fe2(CO)5LNHC(μ- pdt)] 3 (LNHC = 1,3-bis(methyl)-imidazol-2-ylidene, 3a; 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene, 3b) occurs in a single-step, two-electron process at moderate scan rates; under appropriate conditions this process can be separated into two one-electron steps. Density Functional Theory calculations successfully rationalize the effects of the S-to-S linkage on the electrochemistry of the complexes. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

International audience; The bis(nitrile) complex [Mo2Cp2(μ-SMe)3(NCCH3)2](BF4) (1) reacts with HC⋮CCPh2(OH) to give the μ-alkyne product [Mo2Cp2(μ-SMe)3{HC⋮CCPh2(OH)}](BF4) (2). Sequential treatment with triethylamine and tetrafluoroboric acid converts 2 almost quantitatively, via the μ-alkynyl derivative 3, into [Mo2Cp2(μ-SMe)3(μ-η1:η2-CCCPh2)] (BF4) (4), the first example of a dinuclear μ-η1:η2-allenylidene species without carbonyl ligands.

International audience; Reaction of the bis- isonitrile complex [Mo2Cp2(mu-SMe)(3)(xylNC)(2)](BF4) (2b) with NaOH (suspension) under reflux in tetrahydrofuran produced, in quantitative yields, the A-alkylidyne species [Mo2Cp(mu-SMe) (3){mu-(5-C5H4)(xylN)CN(xyl)C}] (4), in which a deprotonated Cp and both isonitrile ligands of 2b are now linked by new C-C and C-N bonds. Under prolonged reflux (72 h) in tetrahydrofuran 2b with either NaOH (suspension) or (Me4N) OH (in MeOH) in the presence of excess isonitrile RNC (R = xyl, Bu-t) was converted in high yields into the mixed (mu-alkylidyne)(mu-amino-oxycarbene) derivatives [Mo2Cp(mu-SMe)(2){mu-(eta(5)-C5H4)(xylN)CN(xyl)C}{mu-eta(1)(O),eta(1)(C)-OCNHR}] (R = xyl (5a1), R = Bu-t (5b2)) and [Mo2Cp(mu-SMe)(2){mu-(eta(C5H4)-C-5)(xylN)CN(xyl)C}{mu-eta(1)(O),eta(1)(C)-OCNMeR}] (R = xyl (6a)). All these products result from hydroxide-isonitrile coupling reactions. When the mixture of 2b, (Me4N) OH (excess), and ButNC (excess) in tetrahydrofuran was heated under reflux for a short time (2 h), complex 5b1 was formed in good yields. Compounds 5b1 and 5b2 are linkage isomers, which differ only in the mode of coordination of the mu-amino-oxycarbene ligand to the Mo1-Mo2 unit; 5b1 converts into 5b2 on prolonged heating. Reaction of the secondary amino-oxycarbene derivative 5a1 with a base (NaOH) and an alkylating agent R"4NBr (R" = Et, Bu-n) afforded the corresponding tertiary(amino)-oxycarbene complexes [Mo2Cp(mu-SMe)(2){mu-(eta(5)-C5H4)(xylN)CN(xyl)C}{mu-eta(1)(O),eta(1)(C)-OCNxylR"}] [R" = Et (6b), Bu-n (6c)]. On heating a tetrahydrofuran solution of the mu-alkylidyne compound 4 with NaOH (suspension) and an excess of either xylNC or (BuNC)-N-t, the mixed mu-alkylidyne and mu-amino-oxycarbene species 5a1 and 5b2 were obtained, demonstrating that 4 is an intermediate in the formation of 5a1 and 5b2 from 2b. Treatment of the mixed isonitrile-nitrile species [Mo2Cp2(mu-SMe)(3)(MeCN)(xylNC)](BF4) (3), containing a labile MeCN group, under reflux in tetrahydrofuran with NaOH (suspension) afforded quantitatively the mu-aminooxycarbene compound [Mo2Cp2(mu-SMe)(3){mu-eta(1)(O),eta(1)(C)-OCNHxyl}] (7). All new complexes have been characterized by elemental analyses and spectroscopic methods, supplemented for 5a1, 5b1, 5b2, 6a, 6b, and 7 by X-ray diffraction studies.

International audience; Reactions of the trinuclear iron cluster [Fe3Cp2(CO)3(μ-CO)(μ3-CO)(μ3-CF3C2CF3)] (1) with the bis(phosphino) ligands dppm and dppe give different results: dppe yields mainly the hexanuclear compound (2) in which two tri-iron cluster units are linked by the diphosphine, although a trinuclear derivative (3) with a chelating dppe ligand is also obtained as a minor product, whereas dppm displaces carbonyl to give complexes containing exclusively a single tri-iron unit, though the phosphine may be either dangling (4) or chelating (5). The complexes 2–5 have been characterised by elemental analyses and from their IR and NMR spectra, supplemented in the case of 2 by a single crystal X-ray diffraction analysis.

The thiolato-bridged binuclear molybdenum complexes [Mo 2 Cp 2 L 2 (μ-SMe) 2 (μ-L′)]Y (Cp = η 5 -C 5 H 5 ; L′ = SMe, L = Bu t NC ( 1a ), xylNC ( 1b ) or CO ( 3 ); L′ = PPh 2 , L = Bu t NC ( 16 ); Y = BF 4 , Cl) react with the anionic reagents NaBH 4 , NaBD 4 , LiR (R = Me, Bu n ), R′MgCl (R′ = Me, Pr i , Bu n or Ph). The products are unsubstituted ( 5 , 7 ) or substituted ( 8 – 12 ) η 4 -cyclopentadiene derivatives, [Mo 2 (η 5 -C 5 H 5 )(η 4 -C 5 H 5 R)L 2 (μ-SMe) 3 ] (L = xylNC, CO), or μ-formimidoyl dinuclear products, [Mo 2 Cp 2 L 2 (μ-SMe) 2 (μ-L′)(μ-CHNR)] (L′ = SMe, L = Bu t NC ( 4 ) or xylNC ( 6 ); L′ = PPh 2 , L = Bu t NC ( 17 )). Since the reduced dinuclear species [Mo 2 Cp 2 (CO) 2 (μ-SMe) 2 ] and the related oxo-compound [Mo 2 Cp 2 (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 (η 5 -C 5 H 5 )(η 5 -C 5 H 4 R)(CO) 2 (μ-SMe) 3 ](BF 4 ) (R = Me ( 13) , Bu n ( 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.

cited By 28; International audience; The 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).

The bis(phosphido)-bridged complex [Fe 2 (μ-PPhH) 2 (CO) 6 ] (1) undergoes double deprotonation to give the phosphorus-centered dianionic derivative [Fe 2 (μ-PPh) 2 (CO) 6 ] 2 - (2) which in turn reacts with the tertiary base RN(CH 2 Cl) 2 to give [Fe 2 {(PPhCH 2 ) 2 NR}-(CO) 6 ] (3) in moderate yield. Treatment of 3 with HBF 4 .Et 2 O affords the N-protonated species [Fe 2 {(PPhCH 2 ) 2 NHR}(CO) 6 ] BF 4 (4). The structural changes to the heavy atom skeleton of 3 arising from protonation are slight, the most obvious being a ca. 0.03 A lengthening of the N-C bonds.

cited By 9; International audience; Treatment 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.

cited By 21; International audience; Reaction of the bis-isonitrile complex [Mo2-Cp2(μ-SMe)3(t-BuNC)2] (BF4) (1) with n-BuLi (in hexane) produced the dealkylated derivative [Mo2Cp2(μ-SMe)3-(t-BuNC)(CN)] (2) in quantitative yield. However, upon treatment with either NaOH (suspension) or (Me4N)OH (in MeOH), 1 was converted into a mixture of 2 and the μ-alkylidyne species [Mo2Cp(μ-SMe)3μ-(η5-C5 H4)(t-BuN)-CN(t-Bu)C] (3), in which a deprotonated Cp and both isonitrile ligands of 1 are now linked by new carbon-carbon and carbon-nitrogen bonds.

The reduction of diazene complexes [Mo(2)Cp(2)(mu-SMe)(3)(mu-eta(2)-H-N=N-R)](+) (R=Ph (3 a); Me (3 b)) and of the hydrazido(2-) derivative [Mo(2)Cp(2)(mu-SMe)(3)[mu-eta(1)-N=N(Me)H]](+) (1 b) has been studied by cyclic voltammetry, controlled-potential electrolysis, and coulometry in THF. The electrochemical reduction of 3 a in the presence of acid leads to cleavage of the N=N bond and produces aniline and either the amido complex [Mo(2)Cp(2)(mu-SMe)(3)(mu-NH(2))] 4 or the ammine complex [Mo(2)Cp(2)(mu-SMe)(3)(NH(3))(X)] 5, depending on the initial concentration of acid (HX=HTsO or CF(3)CO(2)H). The N=N bond of the methyldiazene analogue 3 b is not cleaved under the same conditions. The ability of 3 a but not 3 b to undergo reductive cleavage of the N=N bond is attributed to electronic control of the strength of the Mo-N(R) bond by the R group. The electrochemical reduction of the methylhydrazido(2-) compound 1 b in the presence of HX also results in cleavage of the N=N bond, with formation of methylamine, 4 (or 5) and the methyldiazenido complex [Mo(2)Cp(2)(mu-SMe)(3)(mu-eta(1)-N=N-Me)]. Formation of the last of these complexes indicates that two mechanisms (N=N bond cleavage and possibly H(2) production) are operative. A pathway for the reduction of N(2) at a dinuclear site of FeMoco is proposed on the basis of these results.

cited By 7; International audience; A 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.

cited By 7; International audience; 1-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.

cited By 33; International audience; Reactions of the bis(nitrile) compound [Mo2Cp2 (MeCN)2(μ-SMe)3](BF4) (1) with terminal alkynes in a 1:1 ratio in dichloromethane at room temperature led to the alkyne adduct [Mo2Cp2(μ-SMe)3(RCCH)] (BF4) (2: R = Tol (2a), Ph (2b), CH3C=CH2 (2c), nPr (2d), CO2Me (2e), CF3 (2f)). Compounds 2a-d were readily deprotonated with Et3N to give neutral acetylide derivatives [Mo2Cp2(μ-η1:η2- C≡CR)(μ-SMe)3] (3). Protonation of 3 afforded exclusively the vinylidene complexes [Mo2Cp2(μ-η1: η2-C=CHR) (μ-SMe)3](BF3) (4). Reaction of 1 with an excess of terminal alkyne RCCH in dichloromethane gave either the six-membered metallacycle compounds [Mo2Cp2(μ- η2:η4-CR=CHCR=CHSMe)(μ-SMe)2] (BF4) (5) or the S-methylthiophenium derivatives [Mo2Cp2(μ-η2:η4- C4H2R2SMe)(μ-SMe)2] (BF4) (6), depending on the nature of the R groups. Further reactions of the alkyne adducts 2 with isocyanide and carbon disulfide led to the vinyl-thioether complexes [Mo2Cp2(μ- η1:η3-CR=CR′-SMe)-(μSMe)2 (RNC)](BF4) (7, 8) and to their CS2 adducts [Mo2Cp2(S2C-CR′=CRSMe)(μ- SMe)2]-(BF4) (9, 10), which arise from regioselective C-S coupling. A mechanism is proposed for the formation of the cyclic thiometalla compounds 5, 9, and 10 and of the thiophenium species 6 which assigns a key intermediate role to vinyl-thioether species. The molecular structures of 3a, 4b, and 7a have been established by X-ray diffraction studies.

International audience; Halogens I2, Br2, and Cl2 react with the neutral bridging sulfur site within the Mo2(SMe)2(S) core of the complex [Mo2(η5-C5 Me5)2(μ-S)(μ-SMe)2(CO)2](1) to give covalent halosulfide ligands. The stability of the halosulfide complexes decreases in the order iodine > bromine ≫ chlorine. The stable iodo derivative [Mo2(η5-C5 Me5)2(μ-SMe)2(μ-SI) (CO)2]I5 (2) is the first molydenum(III) compound containing an iodosulfide bridge to be crystallographically characterized.

International audience; The reaction of NaBH4 with the bis-nitrile compound [Mo2Cp2(μ-SMe)3(MeCN)2](BF4) 1 unexpectedly gives rise to the rare, stable μ-(η1-H)(η1-H) tetrahydroborato complex [Mo2Cp2(μ-SMe)3(μ-BH4)] 2, in addition to the expected azavinylidene product [Mo2Cp2(μ-SMe)3(μ-η1-NCHMe)] 3.

International audience; The electrochemical reduction of the imide complex [Mo2(cp)2(μ-SMe)3(μ-NH)]+ (1+) has been investigated in THF and MeCN electrolytes by cyclic voltammetry, controlled-potential electrolysis and coulometry. In the absence of free protons, the electrochemical reduction produces the amide derivative [Mo2(cp)2(μ-SMe)3(μ-NH2)] (2) after consumption of 1 F mol-1 of 1+. In THF in the presence of acid, the reduction of 1+ occurs through a two-electron process. The presence of acid also results in the shift of the equilibrium between 1+ and amide dication 22+ (MeCN electrolyte) or induces an isomerisation of the imide ligand (THF electrolyte). This allows the electrolysis to be conducted at a potential 600 mV less negative than the reduction potential of 1+. Controlled-potential electrolyses in the presence of acid (2 equiv HTsO) produce the ammine derivative. Ammonia is released from these compounds either by coordination of the solvent (MeCN electrolyte) or by the binding of chloride to the ammine-tosylate complex (electrolyses in THF in the presence of acid and chloride). The final products, isolated almost quantitatively (>95%), are [Mo2(Cp)2(μ-SMe)3(MeCN)2] + and [Mo2(cp)2(μ-SMe)3(μ-Cl)], respectively.

International audience; The electrochemical reduction of the phenyldiazene complex [Mo2(cp)2(μ-SMe)3(μ-η2-HNNPh)]+ in the presence of HX (X = TsO, CF3CO2) produces aniline and an ammino derivative. This may involve [Mo2(cp)2(μ-SMe)3(μ-NH)]+ as an intermediate since the imide complex also reduces to the ammino derivative in the presence of HX. These electrochemical steps complete a cycle whereby a phenyldiazenido ligand coordinated to the {Mo2(cp)2(μ-SMe)3+} core is cleaved to PhNH2 and NH3 by successive proton- and electron-transfer steps.

International audience; Removal of a proton from one of the two coordinated acetonitrile ligands in [Mo2Cp2(μ-SMe)3(CH3CN)2](BF4) (1) initiates its intramolecular condensation with the second of the acetonitrile ligands attached to the bimetallic [Mo2Cp2(μ-SMe)3] core, thereby giving rise to the novel μ- η1-azavinylidene complex (Mo2Cp2(μ-SMe)3[μ-η1-N=C(CH3)-CH2CN]) (2). Complex 2 has been characterized by NMR and X-ray methods.

International audience; Iron complexes with the _Fe2(cp)2(μ-SMe)2_ core have been synthesized and their electrochemistry investigated. Electrochemical reduction of the acetonitrile-substituted complexes cis-[Fe2(cp)2(μ-SMe)2(MeCN2) 2]2+ and cis-[Fe2(cp)2(μ-SMe)2(CO)(MeCN)] 2+ labilizes the MeCN ligand(s) and generates vacant sites at which CO and isocyanide substrates can bind. The mechanism of the electrochemical reduction of both complexes has been investigated in the presence of these substrates. A single-crystal X-ray analysis established that cis-[Fe2(cp)2-(μ-SMe)2(CO)(MeCN)][BF 4]2 contains an unusual dication in which different ligands (CO, MeCN) occupy corresponding sites in the co-ordination polyhedra of the two iron centres of the Fe2(μ-S)2 ring. Aspects of the reactivity and electrochemistry of complexes with Fe2(μ-SMe)2 and Mo2(μ-SR)2 cores are compared.

International audience; Rearrangements and protonation reactions of phenyldiazo ligands bound to the bimetallic center, {Mo2Cp2(μ-SMe)3}, are reported

International audience; The synthesis, reactivity, structures and electrochemistry of dimolybdenum complexes jointly stabilized by cyclopentadienyl and bridging thiolate ligands are reviewed. The complexes involved are principally those of molybdenum(II) and molybdenum(III) and they contain from one to four thiolate bridges. It is shown that their reactivity can be controlled by varying the electronic and steric properties of the ancillary ligands and that they provide bimetallic sites for the activation and transformation of various substrates. © 1998 Elsevier Science S.A. All rights reserved.

International audience; The thermal reaction of [Mo2Cp2(μ-SMe)3(μ-Cl)] 1 with NaN3 in THF/EtOH gives a mixture of three compounds [Mo2Cp2(μ-SMe)3(μ-N3)] 2, [Mo2Cp2(μ-SMe)3(μ-NH2)] 3 and [Mo3(O)(N)Cp3(SMe)4] 4. Only the μ-azido derivative 2 is isolated if the time of thermolysis is short. Its formation in the presence of EtOH leads in turn to the products 3 and 4. Production of 3 from 2 requires N2 loss followed by intermolecular reduction of the bimetallic system. Complete decomposition of the complexes occurs if the time of reaction is prolonged. An X-ray diffraction study shows that 4 contains a [Mo2Cp2(μ-SMe)3(μ-N)] core that is linked through a Mo=N double bond to a CpMo(O)(SMe) unit. The resulting Mo3(μ3-N) fragment, in which the N=Mo double bond is supported by two Mo-N single bonds involving the directly bonded metal atoms, is the most striking structural feature of 4. The triply-bridging nitrido nitrogen atom adopts a distorted trigonal planar coordination.

International audience; The dicobalt alkyne complex [Co2(μ-PhC≢CH)(CO)6] 1a reacted with [Mo2(η5-C5H5)2CO)4] in refluxing tetrahydrofuran (THF) to give the μ3-alkylidyne trinuclear cluster [Co2Mo(η5-C5H5)(μ3 -CCH2Ph)(CO)8] 3 as the major product. Possible routes to the formation of 3 have been investigated. Among the identified minor products from this reaction were [CoMo2(η5-C5H5)2(μ 3-CCH2Ph)(CO)7] 4, [Co2Mo2(η5-C5H5)2(μ4-PhC2H)(μ-CO)4(CO)4] 5 and [Co3Mo(η5-C5H5)2(μ 4-PhC2H)(μ-CO)2(CO)5] 6. In contrast, when the related dicobalt complexes [Co2(μ-CF3C≢CR) (CO)6] (R=CF3 (1b), H (1c)), which contain alkynes with more strongly electron-withdrawing substituents, were heated with [Mo2(η5-C5H5)2(CO)4] in THF only mixed-dinuclear complexes [(η5-C5H5)(CO)2Mo(μ-CF3C2R)Co(CO)3](Mo-Co) (R=H (7a), CF3 (7b)) were formed. The reaction of the mixed-dinuclear complex 7b with [Co(η5-C5H5)(CO)2] led to the mixed-tetranuclear butterfly cluster [Co2Mo2(η5-C5H5)3(μ-CO)(CO)3] 8. The thermal reaction of 1b with the phosphido compound [Mo2(η5-C5H5)2(μ-C O)(μ-PPh2)2] gave rise to a single product, [Mo2(η5-C5H5)2(μ-P Ph2)_μ-PPh2Co2(μ-CF3C2CF3)(CO)5₍CO)2] 9, in which a phenyl ring of the (μ-phosphido)dimolybdenum moiety is π-bonded to one of the two cobalt atoms. Spectroscopic data for the new complexes are discussed.

The perfluorosulfanylvinyldiiron(I) complex [{Fe(CO) 3 } 2 {µ-C(SMe)(CF 3 )C(CF 2 )}] 1 reacted with tertiary phosphanes [L = PPh 3 or P(OMe) 3 ] in dichloromethane or chloroform at 60 °C to give high yields of cycloferrathiapentadiene iron clusters. When the nucleophile was PPh 3 , the salt 2 was obtained: formally, a fluoride-ion transfer between two molecules of 1 generates the anion [{Fe(CO) 3 } 2 {µ-C(CF 3 )C(CF 3 )SMe}] - and addition of PPh 3 at two separate sites produces the counter cation [(Ph 3 P)(OC) 2 Fe{µ-CFC(PPh 3 )C(CF 3 )SMe}Fe(CO) 3 ] + . In contrast, with P(OMe) 3 the neutral derivative [{Fe(CO) 3 } 2 {µ-CFC[PO(OMe) 2 ]C(CF 3 )SMe}] 4 was formed. Thermally induced C–F bond activation is a feature of these reactions. All the reaction products have been characterized by elemental analysis and IR, 1 H, 19 F, 31 P and 13 C NMR spectroscopy. The solid-state structure of [(Ph 3 P)(OC) 2 Fe{µ-CFC(PPh 3 )C(CF 3 )SMe}Fe(CO) 3 ][{Fe(CO) 3 } 2 {µ-C(CF 3 )C(CF 3 )SMe }] 2 has been established by single-crystal X-ray analysis. The Fe–Fe bond in the cation [2.716(2) A] is appreciably longer than the corresponding bond in the anion [2.570(2) A]. Possible routes to the formation of 2 and 4 have been investigated. The conversion of 1 into 4 has been shown to involve an intermediate 3 which has been fully characterized by 19 F, 31 P and 13 C NMR spectroscopy.

International audience; Cleavage of the N-N bond of hydrazine by the dimolybdenum centre in [Mo2(η-C5H5) 2(μ-Cl)(μ-SMe)3] 1 gives rise to the amido-bridged complex [Mo2(η-C5H5)2(μ-NH 2)-(μ-SMe)3] 2.

International audience; The thermal reaction of [C5H5Mo(CO)3H] with dimethyl disulfide and allyl chloride has been reinvestigated. In addition to the expected cationic species [(C5H5)2Mo2(μ-SMe)3(CO)2]Cl (1), the new trinuclear complex [(C5H5)Mo(CO)(μ-SMe)3Mo(CO)2(μ- SMe)Mo(CO)2(C5H5)] (2) was obtained. An X-ray diffraction study showed that 2 contains a (C5H5)(CO)Mo(μ-SMe)3Mo(CO)2 core in which the triply bridged Mo-Mo bond is of normal length (2.800(1) Å). This core is linked to the C5H5Mo(CO)2SMe unit via its sulfur atom and through an unusually weak Mo-Mo bond of 3.115(2) Å, the Mo-Mo-Mo angle being 144.5(1)°.

International audience; Oxidative addition of thiols or selenoles across the Mo2 centre of [Mo2Cp2(CO)4] gives complexes with bridging thiolate or selenate and hydride ligands [Mo2Cp2(μ-H)(μ-ER)(CO)4](E S, R Me (4), tBu (5), Bz (6), Ph (7); E Se, R Ph (8)). The complex 4 is also formed on reaction of [Mo2Cp2(μ-SMe)2(CO)4] with vanadocene [VCp2] with the possible involvement of a thioaldehyde, hydride derivative of the vanadocene. Crystals of 4 are monoclinic, space group C2/c, with a = 17.225 (1), b = 8.418 (1) c = 22.960 (2) A ̊, β = 90.346 (5)°, R = 0.023 for 4213 observed reflections. In the solid state, molecules of 4 contain a planar Mo2(μ-H)(μ-S) core and the Cp ligands are cis with respect to the MoMo bond, the two CpMo(CO)2 unites being related by an approximate plane of symmetry which contains the bridging H and S donor atoms and which is normal to the MoMo bond. The fluxional nature of complexes 4-8 in solution is shown from variable-temperature 1H and 13C NMR spectra to arise from cis-trans isomerisation. © 1995.

International audience; The new diamagnetic carbonyl-containing sulfido complex [Cp*2Mo2(CO)2 (μ-SMe)2(μ-S)] (8) has been obtained by the thermal reaction of the pentamethylcyclopentadienyl compound [Cp*2Mo2(CO)4] (1) with MeSSMe; the other predominant product of the reaction, [Cp*2Mo2(CO)4(μ-SMe)2] (3), results from the oxidative addition of dimethyl disulfide across the Mo2 center. Monitoring this thermal reaction by IR spectroscopy indicated that 8 arises from decarbonylative dimerization of [Cp*Mo(CO)3(SMe)] (2). Reactions with other dialkyl and diaryl chalcogenides, REER (ER = SPh, SeMe), and with thiol (HSBz) and selenol (HSePh) led only to the formation of tetracarbonyl chalcogenato-bridged derivatives [Cp*2Mo2(CO)4 (μ-ER)2] (ER = SPh (4), SBz (5), SeMe (6), SePh (7)). A thermolysis study showed the degradation of 3 to [Cp*2Mo2(μ-SMe)4] (12) via [Cp*2Mo2(CO)2(μ-SMe)2] (9); 8 was decarbonylated directly to 12. Investigation of the reaction between 8 and electrophilic reagents showed that dinuclear molybdenum(III) complexes [Cp2*Mo2(CO)2(μ-SMe)2(μ-SH)]X [X = BF4 (16), Cl (17), F(18)] were formed stereospecifically as the cis isomers. 16 has been structurally characterized by X-ray diffraction. Crystals of 16 are orthorhombic, space group Pcab, a = 15.655(5) Å, b = 16.173(3) Å, c = 23.662(5) Å, and Z = 8. The complex cation has approximate C2v symmetry and the Mo-Mo bond length is 2.772(2) Å. Complex 3 was readily oxidized by Ag[BF4] to yield the dicationic product [Cp*2Mo2(CO)4(μ-SMe)2][BF4]2 (21). All new thiolato-bridged complexes have been characterized by spectroscopic analyses. © 1995, American Chemical Society. All rights reserved.