François Y. Pétillon

Influence of a pendant amine in the second coordination sphere on proton transfer at a dissymmetrically disubstituted diiron system related to the [2Fe]H subsite of [FeFe]H2ase.

Studies of the protonation of [Fe2(CO)4(kappa2-PNP)(mu-pdt)] (1; PNP = (Ph2PCH2)2NCH3) by HBF4.Et2O showed that the nature of the reaction product depends on whether the reaction is conducted in acetone or in dichloromethane. In acetone, an N-protonated form, 2, is isolated. Tautomerization of 2 in CH2Cl2 gives rise to a mu-hydride species 3. Variable-temperature NMR experiments have been performed to clarify the processes involved.

Effect of electron-withdrawing dithiolate bridge on the electron-transfer steps in diiron molecules related to [2Fe](H) subsite of the [FeFe]-hydrogenases.

Two hexacarbonyl diiron compounds featuring dithiolate bridges with strong electron-withdrawing groups (CO(2)Me, tetrachloro-biphenyl) were synthesized and structurally characterized. Electrochemical study of these compounds demonstrates that such electron-withdrawing groups have a pronounced effect on both the reduction potentials and the electron transfer process. The reduced forms of these compounds catalyze the reduction of protons in dichloromethane. However, the tetrachloro-biphenyl derivative is the only one able to work in the potential range of its primary reduction process. A catalytic reaction scheme is proposed.

Reactions de quelques cyclopentadienyl methanethiolato fer et ruthenium avec des acetylenes fluores. Mise en evidence d'une double insertion d'un carbonyle et d'un acetylene

[(η5-C5H5)(CO)2Fe(SCH3)] reacts with trifluoropropyne to give a number of products [(η5-C5H5)(CO)2Fe[CC(CF3)]], [(η5-C5H5)(CO)FeC(O)C(CF3)CHS(CH3)], [(η5-C5H5)(CO)FeC(CF3)CHS(CH3)Fe(CO)(η5-C5H5)S(CH3)], [(η5-C5H5)(CO)Fe[(CF3C2H)2SCH3]],[(η5-C5H5)(CO)2Fe[C(CF3)CHSCH3]], [(η5-C5H5)(CO)Fe[(CF3C2H)2S(CH3)]] and [(η5-C5H5)(CO)FeC(CF3)CHS(CH3)] and with hexafluorobut-2-yne to give [η5-C5H5)(CO)FeC(O)C(CF3)C(CF3)S(CH3)]], [(η5-C5H5)(CO)FeC(CF3)C(CF3)S(CH3)], [(η5-C5H5)Fe[η4-CF3C2CF3CF3C2HS(CH3)]] and [(η5-C5H5)(CO)Fe(CF3C2H)(CF3C2CF3)S(CH3)]. With the analogous ruthenium thiolate complex a compound [(η5-C5H5)(CO)RuC(O)C(CF3)C(CF3)S(CH3)] is obtained. Many of the products are heterocyclic compounds containing iron and sulphur. The acetylenic and carbonyl groups readily insert into FeSCH3 bonds and the resultant groups can undergo further insertion by acetylenes.

Reactivite d'alcynes fluores vis-a-vis de methylthiolates [(η5-C5H5)M(SMe)(CO)3] et d'hydrures [(η5-C5H5)MH(CO)3] de molybdene et de tungstene

Abstract The electron deficient acetylene, hexafluorobut-2-yne, reacts with molybdenum and tungsten methanethiolate derivatives (prepared in situ) to give vinyl and three-, five-, or six-membered heterocyclic derivatives: [Cp(OC)- MoC(O)C(CF 3 )C(CF 3 )C(O)S Me], [Cp(OC)2 MC(CF 3 )C(CF 3 )C(CF 3 )C(O)S Me], [CpW(CO)3C(CF3C(CF3)SMe], [CpW{η3- C(CF 3 )C(CF 3 )C(SMe)OC (O)}-(CO)2]. These reactions contrast with those of trifluoropropyne where no organometallic species are obtained. On heating or irradiation with CF3CCCF3 [CpMH(CO)3] gives known bridged species and in the presence of dimethyl disulphide the vinyl derivative [CpM(CO)3C(CF3)C(CF3)H]and an isomer of undetermined structure.

Investigation on the Protonation of a Trisubstituted [Fe2(CO)3(PPh3)(κ2-phen)(μ-pdt)] Complex: Rotated versus Unrotated Intermediate Pathways

The substitution of PPh(3) for a carbonyl group at the {Fe(CO)(3)} moiety in [Fe(2)(CO)(4)(kappa(2)-phen)(mu-pdt)] results in the formation of the trisubstituted complex [Fe(2)(CO)(3)(PPh(3))(kappa(2)-phen)(mu-pdt)] (2). Unlike its tetracarbonyl precursor, the protonation of 2 at low temperature does not afford any apparent transient terminal hydride species. Hydride formation for [Fe(2)(CO)(3)(L)(kappa(2)-phen)(mu-pdt)] (L = PPh(3), CO) species is also studied by density functional theory calculations, which show that activation barriers to give terminal and bridging hydrides can be remarkably close for this class of organometallic compounds.

Molybdenum alkyl- and aryl-thiolates

Abstract The reaction between [(η 5 -C 5 H 5 )MoH(CO) 3 ] and disulphides gives dimeric or trimeric complexes depending upon the conditions. The syntheses of the novel trinuclear molybdenum carbonyl complex [{Mo(η 5 -C 5 H 5 )(SR)(μ-CO)(CO)} 3 ] (R = Me), and dinuclear compounds [Mo 2 (η 5 -C 5 H 5 )(μ-SR) 3 (CO) 4 ] (R = Me) and [Mo 2 (η 5 -C 5 H 5 ) 2 (SR) 2 (CO) 2 (μ-SR)(μ-Br)] (R = Me or Ph) are reported.

Reactions of fluorinated alkynes with the tungsten Hydride [(η5-C5H5)(CO)3WH] II. Phosphine and phosphite substitution reactions and the x-ray structures of the η3-acryloyl complexes [(η5-C5H5)(CO)LWC(O)C(CF3)C(CF3)H], L = CO, P(OMe)3

Abstract Insertion of hexafluorobut-2-yne into the WH bond of the complex [(η5-C5H5)(CO)3WH] yields the η1-vinyl complex [η5-C5-C5H5)(CO)3WC(CF3)C(CF3)H] (I). Migration and insertion of CO into the metal-vinyl bond gives the η3-acryloyl complex [(η5-C5H5)(CO)2 WC(O)C(CF 3 ) C(CF3)H] (II) for which the crystal structure has been determined. Phosphites and phosphines (L = P(OMe)3, PPh3, PMe3, PMe2Ph, PPh2H) displace CO from II to give IIIa in which the η3-acryloyl structure is conserved and CO is adjacent to the acryloyl carbonyl group, as shown by an X-ray analysis of IIIa1, the product with P(OMe)3. Heating IIIa generates the η1-vinyl complexes [(η5-C5H5 )(CO)2 LWC(CF3)C(CF3)H] (IV) whereas prolonged photolysis of IIIa yields isomeric η3-acryloyl compounds (IIIb) in which the phosphorus donor ligands are now adjacent to the acryloyl carbonyl groups.

A dimolybdenum(III) azido compound: its decomposition into amido and nitrido derivatives. Crystal structure of [Mo3(O)(N)Cp3(SMe)4]

Abstract 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.

Reactions of bimetallic group VI complexes: II. Phosphine and phosphite derivatives: Ligand transfer and oxidative decarbonylation; the crystal structure of [(C5H5)(OC)2W(μ-SMe)(μ-I)W(CO)3I]

Triphenylphosphine and trimethylphosphite react with [(C5H5)(OC)2M(μ-SMe)M′(CO)5] (M, M′ = Mo, W) (II) to give [(C5H5)(OC)2)LM(μ-SMe)M′(CO)5] which on heating revert to II. On prolonged heating [(C5H5)(OC)2Mo(μ-SMe)W(CO)4}P(OMe)3}] is formed. [(C5H5)(OC)3W(μ-SMe)W(CO)5] reacts with I2 to give [(C5H5)(OC)2W(μ-SMe)(μ-I)W(CO)3I] for which the crystal structure has been determined.

The effect of replacing carbonyl with acetonitrile on the reactivity of the bimetallic system [Mo2Cp2(μ-SMe)3(L)2]+ (L=CO, CH3CN). Crystal structure of [Mo2Cp2(μ-SMe)2(CH3CN)4](BF4)2

Abstract [Mo2Cp2(μ-SMe)3(CH3CN)2](BF4) (1) reacts with H[BF4] in acetonitrile at room temperature to give the tetrakis (acetonitrile) compound [Mo2Cp2(μ-SMe)2(CH3CN)4](BF4)2 (3) through replacement of one SMe bridge by two terminal CH3CN ligands. In sharp contrast, the carbonyl analogue [Mo2Cp2(μ-SMe)3(CO)2]+ (2) fails to undergo a similar reaction. This suggests that the electronic properties of the ancillary ligands L in the [Mo2Cp2(μ-SMe)3L2]+ moiety govern the activation of a sulfur atom in protonation reactions. An X-ray diffraction study shows that 3 contains two CpMo(CH3CN)2 units bridged by two SMe groups and linked by a long Mo–Mo bond of 3.000(1) A.