R. Poilblanc

A comprehensive study of the system μ-dichlorotetra-carbonyldirhodium-phosphines and evidence of oxidative addition involving new dinuclear complexes☆

Abstract An infrared study has established that the [Rh(CO) 2 Cl] 2 -phosphine (L) systems are composed of two series of complexes, mononuclear complexes X n of formula RhCl(CO) 3- n L n ( n = 1, 2, 3) and dinuclear complexes Y m of formula Rh 2 Cl 2 (CO) 4- m -L m ( m =0,1,2,3,4). The new compounds Y 2 and Y 3 are sufficiently stable to allow elemental analysis but for the compounds X 1 and Y 1 proof of their structures has been obtained by chemical methods and by mass spectrometric investigations. Preliminary PMR studies indicate that quite fast and complex exchanges occur in the system. Reactions of Cl 2 , HCl and CH 3 I molecules on dinuclear complexes are examples of oxidative additions to two coordinative metal centers.

Complexes du titane et du zirconium contenant les ligands cyclopentadienyldiphenylphosphine et cyclopentadienylethyldiphenylphosphine: acces a des structures heterobimetalliques

Abstract Reactions of Ph 2 P(CH 2 ) n (C 5 H 4 )Li, ( n = 0, 2), with MCl 4 or CpTiCl 3 (M = Ti, Zr; Cp = η 5 -C 5 H 5 ) form Cl 2 M[(η 5 -C 5 H 4 )(CH 2 ) n PPh 2 ] 2 or Cl 2 CpTi[(η 5 -C 5 H 4 )-(CH 2 ) 2 PPh 2 ] in good yields. Chemical reduction with Al, or electrochemical reduction of these complexes, under CO, are described. The titanium(IV) and zirconium(IV) derivatives react with metal carbonyls (Mo(CO) 6 , Cr(CO) 6 , Fe(CO) 5 , Mo(CO) 4 (C 8 H 12 )) under formation of new heterobimetallic complexes. Reduction with Al of Cl 2 CpTi[(η 5 -C 5 H 4 )(CH 2 ) 2 PPh 2 ]Mo(CO) 5 under CO results in a new heterobimetallic species containing low valent titanium. Both complexes Cl 2 M[(η 5 -C 5 H 4 )(CH 2 ) 2 PPh 2 ] 2 (M = Ti, Zr) react with [Rh(μ-Cl)(CO)(C 2 H 4 )] 2 to yield {RhCl(CO)(Cl 2 M[(η 5 -C 5 H 4 )(CH 2 ) 2 PPh 2 ] 2 )} x , which is assumed to be a dimer, in which the titanium or the zirconium compounds act as bridging diphosphine ligands between the rhodium atoms.

Electrochimie des composes organometalliques des metaux de transition

Resume Les resultats electrochimiques obtenus sur les composes organometalliques des metaux de transition pendant la periode 1950–1976 sont presentes ainsi que 290 references sur le sujet. Nous avons tente de relier les mecanismes connus des processus doxydation et de reduction electrochimique. Il apparaǐt au cours de ce travail que si de nombreuses etudes sont consacrees a la reduction electrochimique, il existe par contre encore peu detudes doxydation anodique dans le domaine prometteur des metaux de transition de faible degre doxydation. Cette revue rappelle les mecanismes redox et apporte des informations cinetiques sur les differentes etapes du processus global a lelectrode quand elles sont connues. Dans la plupart des cas, le probleme de la determination de lorbitale moleculaire concernee par le transfert electronique nest pas resolu. Parmi les publications citees en premiere partie, de nombreux travaux ont trait a leelectrochimie des metallocenes ou des metaux carbonyles, mais peu detudes sont consacrees a lelectrochimie des metallocarboranes, des carbynes, des ylures et des clusters. La seconde partie de cette revue developpe deux applications de lelectrochimie des composes organometalliques: lelectrosynthese de complexes metalliques et la generation in situ de catalyseurs organometalliques. Des exemples sont choisis pour illustrer les possibilites offertes par cette derniere methode en particulier pour la polymerisation et loligomerisation en synthese organique.

Electrochemical investigation of coordination compounds: II. Phosphine derivatives of Co0 and Ni0. Correlations between E12, ΔHNP and v(CO) in these complexes☆

Abstract The complexes [Co(CO) 3 L] 2 , Hg[Co(CO) 3 L] 2 , HgCo 2 (CO) 8− n L n and Ni(CO) 4− n L n (L = PR 3 , P(OR) 3 ) have been reduced electrochemically. The E 1 2 values of the reduction processes are dependent on L and n . These values can be related to the ΔHNP values of the ligands and to the CO stretching frequency of the molecules. The results can be interpreted in terms of either kinetic or thermodynamic factors.

Protonation of the metal—metal bond in Fe2(μ-A)(μ-A′)(CO)4L2 complexes (A A′ SC6H5, P(C6H5)2, P(CH3)2; A SC6H5, A′ z.dbnd; P(C6H5)2; L z.dbnd; P(C6H5)3-n(CH3)n). : III. Experimental study of the influence of the A and A′ bridges on the basicity of the metal—metal bond

Abstract In order to check the influence of the bridges on the basicity of the metal—metal bond in Fe 2 (μ-A)(μ-A′)(CO) 4 L 2 complexes, the compounds with A ue5fb A′ue5fb SC 6 H 5 , P(C 6 H 5 ) 2 ; P(CH 3 ) 2 ; A ue5fb SC 5 H 5 , A′ue5fb P(C 6 H 5 ) 2 and L ue5fb P(CH 3 ) 3-n (C 6 H 5 ) n ( n ue5fb 0—3) have been prepared. IR and PMR spectroscopic results are interpreted in structural terms, and show that the Fe 2 (SC 6 H 5 )(P(C 6 H 5 ) 2 .)-(CO) 4 L 2 complexes are non rigid on the NMR time scale for n = 0, 1. Replacement of the first SC 6 H 5 bridge by a P(C 6 H 5 ) 2 bridge markedly increase the basicity of the metal—metal bond, but replacement of the second SC 6 H 5 bridge has no significant effect.

Electrochemical behaviour and chemical oxidation study of the thio- and phosphido-bridge binuclear iron complexes

Abstract The electrochemical behaviour of thio and phosphido complexes of iron(I): Fe2XY(CO)6ue5f8nLn (X = Y = SR, PR2 and X = SR, Y = PR2, L = PR3) has been studied on platinum and mercury electrodes, in organic solvent. These complexes are reduced in a two-electron irreversible process. A large difference is observed between their oxidation potentials on mercury and platinum electrodes; this is ascribed to the formation of a mercury complex in which mercury is inserted into the metalue5f8metal bond. In oxidation on platinum electrodes, two mono-electronic waves are observed. The influece of the ligand basicity on the cathodic E 1 2 values is discussed. A parallel shift is observed between the E 1 2 and the IR ν(CO) of the totally symmetrical mode. Chemical oxidation of the complexes shows that the dications cannot be isolated, and leads to isolation of the following species: [FeP(CH3)2(CO)3]2AgNO3, [FeSCH3(CO)2P(CH3)3]2(NO3)2, {[FeSCH3(CO)2P(CH3)3]2F} PF6, where NO3− and F− act as ligands.

Polyfluorothiolate derivatives of rhodium(I). Crystal and molecular structure of [Rh(μ-SC6HF4)(C8H12)]2

SummaryThe thiolato-bridged dinuclear compounds [Rh(μ-SR)-(COD)]2, where R=p-C6HF4 (1),p-C6H4F (2) and CF3 (3), are obtained from the chloro-bridged analogue by ligand exchange.Compound (1) crystallizes in the space group P1 with a=9.740(3)Å, b=11.642(4)Å, c=13.997(6)Å, α=103.87(3)°, β=106.98(3)° and γ=105.10(2)°; z=2. In this dinuclear molecule both Rh atoms have a square planar coordination sharing one edge, namely the two sulphur bridging atoms. The Rh—Rh separation of 2.96 Å is consistent with at most a very weak metal-metal interaction. Upon addition of CO the dimeric [Rh(μ-SR)(CO)2]2 (4), (5) and (6) are obtained, but addition of PPh3 affords the monomeric species [Rh(SR)(PPh3)-(COD)] (7), (8) and (9). Reactions of the dimeric tetracarbonyl derivatives with PPh3 vary with the nature of R; [Rh(μ-SR)(PPh3)(CO)]2 is obtained when R=p-C6H4F (10) and CF3 (11) but monomeric [Rh(SR)-(PPh3)(CO)2] (12) is produced when R=p-C6HF4. The latter mononuclear compounds, with R=p-C6H4F (13) and CF3 (14), are also formed by reaction of [Rh(SR)-(PPh3)(COD)] with CO.

Interactions of chlorine and bromine with chemisorbed carbon monoxide on evaporated platinum, rhodium, and iridium films

The action of bromine and chlorine on surface carbonyl complexes of platinum, rhodium, and irdium has been studied by ir spectroscopy. At room temperature chlorine and bromine cause partial removal of chemisorbed CO molecules, and produce two other main effects. The stretching frequency of the remaining CO molecules progressively shifts to higher values, corresponding to an increase of the CO bond strength, due to a lowering of the electron back donation dπ → 2π∗ from the metal to the 2π∗ antibonding orbitals of the chemisorbed CO molecules. This electron-withdrawing ligand effect of halogen is a long-range effect which uses the collective properties of the metal surface. In the case of Rh and Pt, new carbonyl species which exhibit ir bands at higher frequencies (range 2100–2135 cm−1) have also been detected; the corresponding metal atoms are oxidized. The observation that these metal atoms are insensitive to the ligand electron-donor effect of P(CH3)3 is justified in terms of “demetallization”.

Dinuclear bridged d8 metal complexes : IX. Preparation and structure of the complexes [Ir2(μ-SBu-t)2(CO)2(PR3)2] and [Ir2(μ-SBu-t)2(CO)3(PR3)]

Abstract The addition of two moles of a tertiary phosphine ligand PR 3 to [Ir 2 (μ-SBu-t) 2 (CO) 4 ] affords the dinuclear disubstituted iridium(I) complexes [Ir 2 (μ-SBu-t) 2 (CO) 2 (PR 3 ) 2 ]. 1 H, 13 C and 31 P and infrared data are consistent with a bent geometry, the CO groups being in cis dispositions and the t-butyl groups in anti dispositions. When R = OMe exchange between this isomer and the trans-anti isomer occurs in solution. For R = Ph one isomer, possibly a trans isomer, which is transformed irreversibly into the cis isomer, is detected. An intermediate complex is observed during substitution, and its spectroscopic data are consistent with the formula [Ir 2 (μ-SBu-t) 2 (CO) 3 (PR 3 )]. This complex is in equilibrium with the parent complex and [Ir 2 (μ-SBu-t) 2 (CO) 2 (PR 3 ) 2 ], and NMR data suggest that it is an anti isomer.

Tervalent phosphorus derivatives of cobalt carbonyls : IV. Comparison of the reactions of phosphites and phosphines with dicobalt octacarbonyl☆

Abstract The reaction of dicobalt octacarbonyl with tertiary phosphites gives several products, which have been interconverted by chemical means. Some cobaltue5f8cobalt bonds have been formed from the nucleophilic attack by the anion [Co(CO)4−nLn]− on the cation [Co(CO)5−n(PR3)n]+ leading to known binuclear compounds. Such a reaction is not possible with tertiary phosphites because of a Michaelis—Arbuzov rearrangement, previously observed for complexes of manganese and molybdenum.