Showing papers by "Jacques E. Guerchais published in 1982"

Oxidation of iron and molybdenum naphthalocyanines. X-ray photoelectron studies in relation to the electrocatalysis of oxygen reduction and evolution

Abstract: C 1s, N 1s, O 1s, Fe 2p and Mo 3d X-ray photoelectron core-level spectra of newly synthesized iron and molybdenum naphthalocyanines have been recorded following exposure to air for different times. The observed modifications of the C 1s and N 1s lines provide information on the electronic structure perturbations related to dioxygen fixation, and the intensity and shape of the O 1s, Fe 2p and Mo 3d peaks provide information on the rates of oxidation, the coordination number of the central metal ion and the kinetics of oxygen penetration into the bulk. From these X.p.s. results, new methods are suggested for the synthesis of compounds of electrochemical interest.

The formation, structure, and reversible carbonylation of [(η5-C5H5)MM′(CO)7(SR)] complexes; reactions of [(η5-C5H5)MM′(CO)8(SR)] with hexafluorobut-2-yne

Abstract: The action of heat on [(η5-C5H5)(OC)3M(µ-SR)M′(CO)5](1)(M or M′= Cr, Mo, or W; R = Me or Ph) gives [(η5-C5H5)(OC)2[graphic omitted](CO)5](2) containing a metal–metal bond. Photolysis of (2) in the presence of carbon monoxide regenerates (1) in an example of reversible cleavage of a M–M bond by carbon monoxide. The octacarbonyls (1) react with hexafluorobut-2-yne to give products of substitution at the (η5-C5H6) M group. The spectroscopic parameters of the complexes and crystal-structure analyses of (1a; M = M′= W, R = Me), (2b; M = Mo, M′= W, R = Me), and [(η5-C5H5)(OC)(CF3C2CF3)W(µ-SMe)W(CO)5](5) are discussed in terms of the electronic properties of the bridging thiolato-group and the metal centres.

Bis(cyclopentadienyls) with transition metal–mercury bonds. Part 4. Formation of niobium–mercury bonds and X-ray crystal structure of [Nb(η-C5H5)2{HgS2CN(C2H5)2}3]

Abstract: In aromatic solvents (toluene or benzene–toluene) reaction of [Nb(η-C5H5)2H3], prepared in situ, with a variety of mercury(II) salts at room temperature yields complexes with two or three Nb–Hg bonds. The product of the reaction with [Hg(S2CNEt2)2] is [Nb(η-C5H5)2(HgS2CNEt2)3](1), which has been characterised by single-crystal X-ray diffraction. Complex (1) crystallises in the monoclinic space group P21/n with a= 12.302(10), b= 18.385(11), c= 16.077(5)A, β= 108.18(5)° and Z= 4. The structure has been solved by heavy-atom methods and refined to R 0.072 for 2 876 unique observed diffractometer data [l > 2σ(l)]. The molecule consists of a rhomboidal tetrametal cluster formally derived from [Nb(η-C5H5)2H3] by replacement of each hydride ligand by an Hg(S2CNEt2) moiety. The dithiocarbamate ligands chelate the mercury atoms asymmetrically with the shorter, stronger Hg–S bond trans to the niobium atom and the ligand plane approximately perpendicular to the NbHg3 plane. The Nb–Hg distances are indicative of single bonds (mean 2.790 A), whilst the Hg–Hg separations average 2.892 A.The reaction of HgX2(X = Cl, Br, or l) with [Nb(η-C5H5)2H3] gives [Nb(η-C5H5)2H(HgX)2]·xHgX2, (2)–(4)(x= 0.5 for X = Cl, x= 1 for X = Br, and x= 0.66 for X = l). Although these adducts do not undergo direct substitution of X by thiolates, the thiolate analogues [Nb(η-C5H5)2H(HgSR)2][R = Et (5) or But(6)] are accessible via reaction of the trihydride with [Hg(SR)2](R = Et or But). Products (2)–(6) have been characterised by analytical, 1H and l3C n.m.r. data.