René Rumin

Le complexe [{PtCl2(triméthyl-2,4,6-pyridine)}2] catalyseur homogene d'hydrogenation et d'hydrosilylation d'olefines et d'aldehydes et cetones α,β-insatures

Abstract The chloro-bridged platinum(II) complex dichlorobis(2,4,6-trimethylpyridine)-platinum was found to be an active catalyst for homogeneous hydrogenation and hydrosilylation of olefins and α,β-unsaturated aldehydes and ketones at room temperature and under atmospheric pressure. Hydrosilylation of terminal olefins can be achieved with dimethylphenylsilane and a catalyst/reactant ratio of 10 −6 /1. This complex is the first example of a platinum(II) compound containing pyiridine ligands having good catalytic activity possibilities.

Photochemistry of polyenes. Control by orbital symmetry and ground state conformations

Abstract It is shown that ground state conformations of cyclohexadienes and acyclic hexatrienes play an important role, in addition to orbital symmetry factors, to govern the stereochemistry of the photoisomerization reactions of these compounds. Studying the influence of the wave-length of irradiation allows to attribute to discrete conformations some specific photoreactions (H shift, formation of bicyclo {3.1. 0} hexene). New examples are given, with kinetic data, showing a {4π a + 2π a} stereospecificity for the hexatriene Photo-DIELS-ALDER reaction with a predominent orbital control. The concertedness of the reaction is discussed. Kinetics of Z, E-photoisomerizations around C-C double bonds of hexatrienes are shown, in relation with the ease of terminal compared to central double bonds rotations. Singlet and triplet states have different behaviours in this respect, as well as different wave-lengths of excitation.

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

The reactions between alcohols ROH (R = Me, Et) and RR(OH)2 (RR = CH2−CH2) and the [perfluoro(sulfanyl)vinyl]diiron complex [{Fe(CO)3}2{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)3}2{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)3}2{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)3}2{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)3}2{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)] 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)3}2{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)3}2{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.

Carbonfluorine bond activation by iron(I). CF bond cleavage induced by addition of phosphines or thiols to a perfluorovinyldiiron complex

Abstract The reaction of phosphines PXYH (X  Y  Ph, i-Pr; X  Ph, Y  H) or ethanethiol with the perfluorovinyl compound [{Fe(CO)3}2{μ-C(SMe)(CF3)CCF2}] (1) proceeds with cleavage of one CF bond and gives rise to unusual ligand transformations. The multicenter processes involved lead to new diiron complexes [{Fe(CO)3}2{μ-C(SMe)(CF3)C(PXY)CF}] (X  Y  Ph, 2a; X  Y-i-Pr, 2b; X  Ph, Y  H, 2c) and [{Fe(CO)3}2{μ-C(SMe)(CF3)C(SEt)CF}] (3). Mechanisms for these reactions are proposed. The fluxional behavior of 2a and 3 has been investigated by variable-temperature 13C NMR spectroscopy. The molecular structure of 2a has been established by a single-crystal X-ray diffraction study. The Fe2(CO)6 core contains an FeFe bond of 2.633(1)A bridged by the six-electron donor C(SMe)(CF3)C(PPh2)CF ligand. 2a crystallizes in the triclinic space group P 1 with a = 9.019(2), b = 9.550(2), c = 18.583(3) A , α = 101.06(2), β = 92.53(2), γ = 116.48(2)°, R = 0.0419 for 3984 reflections.

Specific formation of isocyanide iron complexes by reaction of primary carbamoyl ferrates with oxalylchloride

Abstract Reaction of primary carbamoyl ferrates {(CO) 4 Fe[C(O)NHR]} − (R=Me, Et, allyl, decyl, cyclohexyl, t-butyl, benzyl, phenyl) with 1/2 equiv. of oxalylchloride affords cis -bis-carbamoyl intermediates: (CO) 4 Fe[C(O)NHR] 2 which thermally give rise, in good yields, to the mono-isocyanide complexes (CO) 4 Fe(CNR). The mechanism of the reaction is discussed. Via a similar process, an alkoxycarbamoyl intermediate (CO) 4 Fe[C(O)NHR](CO 2 Me) affords Fe(CO) 5 and 1,3-dialkylurea.

Novel ligand transformations in cluster complexes. Activation of C–F bonds in a perfluorovinyldiiron(I) complex by primary and secondary amines

Reactions of primary amines with the perfluorovinyl complex [{Fe(CO)3}2{µ-C(SMe)(CF3)CCF2}]1 proceed with cleavage of two C–F bonds to give 2, whereas with secondary amines fluorine migration and C–F bond rupture afford the novel organometallic complex 3; both 2 and 3 have been characterized by X-ray analysis.

Ligand shift in mixed-cluster complexes: synthesis of alkyne-bridged Co2Mo2 clusters with two triply-bridging sulphur atoms: crystal structure of [Co2Mo2(η5-Cp)2(μ3-S)2(μ4-CF3C2Me)(CO)4]

Abstract Reaction of the complexes [(CO) 3 Co(μ-RC 2 R′)Co(CO) 3 ] (R = R′ = CF 3 ; R = Ph, CF 3 and R′ = H) with the MoMo dinuclear derivative [Mo 2 Cp 2 (μ-SMe) 2 (CO) 2 ] leads to cleavage of both CS and CH bonds with the formation of closo -octahedral Mo 2 CO 2 C 2 clusters stabilised by a μ 4 -η 2 -bound alkyne. An X-ray diffraction study has shown that the two Mo 2 Co faces of the octahedron are capped by triply-bridging sulphur atoms.

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

Abstract Treatment of either the μ-alkyne complex [Mo2Cp2(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-η1(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.

Reactions of the μ-alkyne-dicobalt complexes [Co2(CO)6(μ-CF3–CC–R)] (R=CF3, H) with [Co2Cp2(μ-SMe)2]: substitution and insertion leading to novel thiolato-alkyne tetra- and tricobalt clusters

Abstract The bis(μ-thiolato)dicobalt complex [Co2Cp2(μ-SMe)2] (1) reacts with alkyne-cobalt complexes [Co2(CO)6(μ-F3CCCR)] (2) to give tri- and tetranuclear cobalt cluster compounds. When R=CF3 the main product is [Co2(CO)4(μ-CF3C2CF3){μ-Co2Cp2(μ-SMe)2}] (3) but the trinuclear cluster [Co3Cp(CO)4(μ-SMe)2(μ-CF3C2CF3)] (4) is also obtained in low yield. When R=H the products are the isomeric clusters [Co3Cp(CO)4(μ-SMe)2(μ-CF3C2H)] (5 and 6), [Co3Cp2(CO)3(μ-SMe)(μ-CF3C2CH)] (7) and [CpCo(CO)2]. The solid state structures of 3, 4, 5 and 7 have been established by X-ray analysis. The 50 electron triangular cluster 4 has weak Co–Co bonds [2.573(1), 2.800(1), 2.838(1) A]. The alkyne ligand bridges the shortest of these bonds in perpendicular fashion. 5 and 7 contain open chain tricobalt units [Co–Co 2.39–2.57 A] more typical of 50 electron M3 species. In these complexes the alkyne is π-bonded to the central metal atom and σ-bonded to both terminal cobalt atoms. Variable temperature NMR indicates that 5, 6 and 7 each exist in solution as interconverting isomers which differ in the configuration at one sulphur atom. For 5 the activation parameters [ΔH‡=64 kJ mol−1 and ΔS‡=−85 J K−1 mol−1] were obtained spectroscopically. In the solid, molecules of 7 contain an asymmetrically bridging carbonyl [Co–C 1.833(4) and 2.050(3) A] which is not detectable in the solution spectra.

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

Abstract 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.