Bernard Gautheron

Structural diversity in coordination chemistry of tridentate and tetradentate polyphosphines of Group 6 to 10 transition metal complexes

Abstract Tridentate and tetradentate polyphosphines offer a huge variety of coordination modes to transition metals which lead, depending on the metal, to very different structural features in the resulting complexes. Steric effects being crucial in metal–phosphine complexes reactivity, a good knowledge of the molecular structures of the species is required both in the solid state and in solution. This article reviews from a structural point of view the monometallic and symmetrical homobimetallic complexes of the transition elements of Group 6 to 10 with tridentate and tetradentate phosphines. Concerning the classical triphosphines and tetraphosphines, emphasis was put on advances reported after the year 1994, since comprehensive reviews have covered the former period. Several anterior relevant results are, however, briefly mentioned when necessary. A second part is devoted to nitrogen- and sulfur-containing derivatives potentially tridentate and tetradentate ligands, and their coordination to the above-mentioned metals. The last part describes the complexes obtained with the less classical ferrocenyl polyphosphine ligands or their nitrogen-containing derivatives: each ligand having a potential tridentate or tetradentate coordination from either phosphorus or nitrogen donor atoms. The literature cutoff date was during the second half of 2000, but in a few cases, references to important work appearing during 2001 were made; however such coverage should be completed in a future compilation. An exhaustive quoting of catalytic applications and reaction chemistry was beyond the scope of this article mainly devoted to structural works. Nevertheless, in order to illustrate the importance of this chemistry, efforts were made to provide the reader with recent references that have marked the field, even in the absence of X-ray structural characterization.

New 1,1%- or 1,2- or 1,3-bis(diphenylphosphino)ferrocenes

The syntheses of ferrocenyl phosphines with bulky substituents are reported using the reaction between FeCl2 and the suitably substituted cyclopentadienyl salts, LiC5H3-1,3-(PPh2)2, LiC5H3-1-PPh2-3- t Bu, LiC5H2-1,2-(PPh2)2-4- t Bu. This strategy leads to bi-, tri- and tetraphosphines, which cannot be obtained by the other access paths used to prepare substituted ferrocenes. [C5H3-1,3(PPh2)2](C5H5)Fe, [C5H3-1-PPh2-3- t Bu]2Fe racemic and meso and [C5H2-1,2-(PPh2)2-4- t Bu](C5H5)Fe have been characterized by single-crystal X-ray diffraction studies.

New potentially cytotoxic thiolatogold(I) complexes of 1,1′-bis(diphenylphosphino)ferrocene

Abstract 1,1′-Bis[chlorogold(I) diphenylphosphino] ferrocene (1) was chosen as the starting material to synthesize new thiolato gold(I) complexes. This has been achieved by substituting the chlorine atoms by monofunctional and bifunctional thiolates affording ‘open’ thiolatogold complexes and trimetallic ferrocenophane-type structures, respectively. The new 1,1′-bis(2,6-dithia-1-phosphanyl)ferrocene (7) containing directly linked P and S atoms was also prepared but no gold complex was obtained. Compound 2 crystallizes in the monoclinic space group P21/n with a=10.2632), b=21.064(4), c=16.259(3) A , β=97.06(2)° and V=3.488(1) A 3 . The distance between the two gold atoms (3.06 A) indicates a significant contact interaction. Compounds 2–5 have allowed antitumoral efficiency on human bladder and colon carcinoma.

Rhodium and palladium complexes from 1,1′ and 1,2 ferrocenylphosphine as bidentate ligands. Versatile coordination

Abstract The complexation of the mixed bidentate ligands 1-diphenylphosphino-1′-diphenylthiophosphinoferrocenyl and 1,2-bis(diphenylphosphino)ferrocenyl with rhodium(I) and palladium(II) species yield a range of mono- and dirhodium or palladium complexes. Their interest as possible catalysts for alkene hydroformylation and alkoxycarbonylation and Heck coupling reactions has been assessed. Fe[C5Me4P(S)Ph2][C5Me4PPh2]PdCl2 and Fe[C5H2-1,2-(PPh2)2-4-tBu][C5H5]PdCl2 have been characterized by single-crystal X-ray diffraction studies.

Cyclopentadiene with two coordinating sites: 1,5-bis(diphenylphosphino) -2,3,4-trimethylcyclopenta-1,3-diene

Abstract The possibility of obtaining the new bidentate 1,2-diphenylphosphinocyclopentadienyl ligand has been studied. 1,5-bis(diphenylphosphino)-2,3,4-trimethylcyclopenta-1,3-diene can be formed from butanone and chlorodiphenylphosphine in eight steps. The results of chemical and spectroscopic studies reveal that a 1.5-sigmatropic migration of the diphenylphosphino group takes place: the 1,2-diphenylphosphino-substituted species are converted into 1.3 species.

An easy route to 1-germaindenes via a transmetallation zirconiumgermanium reaction

Abstract Several 1-zirconaindenes ( 4 ) have been obtained easily by heating phenylmethylzirconocene with various symmetrical (R ue5fb R′ ue5fb CH 3 , C 2 H 5 , n-C 3 H 7 , Si(CH 3 ) 3 and unsymmetrical (R ue5fb CH 3 , R′ ue5fb Si(CH 3 ) 3 ) alkynes (Rue5f8Cue5fcCue5f8R′). Under similar experimental conditions, the ynamine, diethylaminotrimethylsilylethyne, led to a regioselective reaction. From the X-ray structure of the zirconaindene product, the trimethylsilyl group was found close to the zirconium atom. Compounds 4 with germanium tetrachloride afford new 1-germaindenes ( 7 ) characterized by 1 H and 13 C NMR and mass spectrometry, in good yield.

SYNTHESIS OF SELENIUM-CONTAINING CROWN ETHERS AND RELATED COMPOUNDS

Abstract The synthesis of the first examples of selenium-containing crown ethers from the benzene diselenolate anion and dichalcogenated ethers is reported. The reaction is highly dependent on the experimental conditions, particularly the concentration. 1H NMR and mass spectrometry were used to confirm the structures of the new compounds.

Thermal stability and reaction of chalcogen-containing metallocenic compounds with elemental chalcogens

Abstract Dissymmetrical four-membered bimetallocenacycles (t-BuC 5 H 4 ) 2 M(μ-S) 2 M′-(RC 5 H 4 ) 2 (M, M′ = Zr, Hf; R = H, t-Bu) have been prepared and found to give redistribution products in solution at 190°C; identification of these products shows that the reaction involves exclusive cleavage of a metal-sulfur bond. Elemental sulfur and selenium react with chalcogen-containing complexes. The reaction is shown to involve the introduction of chalcogenic species in place of the σ-ligands of the complex to give either four-membered bimetallic complexes or catenated pentachalcogen metallocenic compounds. Some examples of insertion of sulfur and tellurium into the zirconium-methyl bond are also described.

Composés métallocèniques chalcogènés: action des dihydrures de zirconocène et de hafnocène sur le soufre, le sélénium et le tellure

Resume Dimeric zirconocene and hafnocene dihydrides [(η 5 -RC 5 H 4 ) 2 M(H)(μ-H)] 2 (M = Zr, Hf) react with grey selenium or tellurium to afford the known four-membered bimetallacyclic compounds [(η 5 -RC 5 H 4 ) 2 M(μ-E)] 2 (E = Se, Te) as the sole organometallic products. In the case of sulfur the first step of the reaction is shown to involve the insertion of a chalcogen atom into the metal-hydrogen bonds to give the bis-hydrogenosulfide (η 5 -t-BuC 5 H 4 ) 2 M(SH) 2 (M = Zr, Hf), which reacts either with the starting dihydride to give [(η 5 -t-BuC 5 H 4 ) 2 M(μ-S)] 2 or with the unchanged sulfur to afford the metallacyclohexasulfane (η 5 -t-BuC 5 H 4 ) 2 MS 5 and hydrogen sulfide. These last two compounds react further with the dihydride. The reactions above have been studied starting from authentic compounds, prepared for this purpose by unambiguous methods. In the case of selenium and tellurium no intermediate product could be detected and the difference with sulfur is explained in terms of the solubility of the chalcogen in the solvent.

1,1′,2,2′-Tetrakis(diphenylphosphino)-4,4′-di-tert-butylferrocene, a new cisoid arrangement of phosphino groups

Abstract The action of two equivalents of 1,2-bis(diphenylphosphino)-4- tert -butylcyclopentadienyllithium on FeCl 2 led to the corresponding 1,1′,2,2′-tetraphosphinoferrocene. The X-ray structure of this bulky ferrocene is described. The spectroscopic results reveal a conformational chirality with a cisoid disposition of the phosphino groups. The first results about the complexation with representative elements of Group IX and X (Rh, Pd, Ir) are reported.