Roland Broussier

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.

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.

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.

Synthesis of bis(diphenylphosphinocyclopentadienyl) yttrium chloride complexes and heterodimetallic derivatives. X-ray structure of bis[(μ-chloro)bis(diphenylphosphinocyclopentadienyl) yttrium(III)]

Abstract Reaction of lithium diphenylphosphinocyclopentadienide with YCl 3 or YCl 3 (THF) 3 and working lead to the formation of three yttrocene phosphines: the lithium metal adduct isolated as (Ph 2 PC 5 H 4 ) 2 Y(μ-Cl) 2 Li(THF) 2 · 0.5 LiCl ( 1 ), the chloride-bridged dimeric species {(Ph 2 PC 5 H 4 ) 2 Y(μ-Cl)} 2 ( 2 ), and the coordinated monometal species [(Ph 2 PC 5 H 4 ) 2 YCl(THF)] ( 3 ). The X-ray structure of 2 is remarkable in that the crystal exhibits two independent chloride-bridged dimers that differ in the arrangement ( syn, anti ) of the diphenylphosphino groups. Chelation of phosphorus atoms to a molydenum carbonyl moiety is also reported.

Group 4 and Group 8 unbridged metallocene derivatives with a pendant fluorenyl group. X-ray structure of 1,1′-bis[2-(2-fluorenyl)propyl]ferrocene

The action of one equivalent of BuLi on 2-cyclopentadienyl-2-fluorenylpropane (C 5 H 5 CMe 2 C 13 H 9 ) led to the monoanionic salt LiC 5 H 4 CMe 2 C 13 H 9 . This anion was reacted with Fe 2 Cl 4 (THF) 3 , TiCl 3 (THF) 3 , ZrCl 4 , HfCl 4 or CpZrCl 3 , DME and, in a mixture with CpLi, with Fe 2 Cl 4 (THF) 3 affording the corresponding metallocenes and metallocene dichlorides. The X-ray structure of Fe( η 5 -C 5 H 4 CMe 2 C 13 H 9 ) 2 is described. The first results about the reactivity of the fluorenyl group are reported together with the synthesis of Zr( η 5 -C 5 H 5 )[ η 5 -C 5 H 4 CMe 2 - η 5 -C 13 H 8 Rh(cod)]Cl 2 , which has been tested using hydroformylation and cyclotrimerisation catalysis.

Novel group 4b ansa-metallocene complexes with the shortest bridge: [1,1′-isopropylydene-3,3′-di-t.Bu-bis(η5-cyclopentadienyl)] Ti and Zr dichlorides

Abstract Reaction of [1,1′-isopropylidene-3,3′-di- tert .butyl-bis( η 5 -cyclopentadienide)] dilithium with TiCl 3 , followed by treatment with HCl, and ZrCl 4 in various solvent mixtures in the temperature range 0–50°C gives corresponding ansa -metallocene dichlorides as mixtures of the anti / syn -isomers, 1:1. The crystal and molecular structures of three of the four isomers were determined, i.e. rac( anti )-[1,1′-isopropylidene-3,3′-di- tert .butyl-bis( η 5 -cyclopentadienyl)]TiCl 2 , space group B 2/ b , rac( anti )-[1,1′-isopropylidene-3,3′-di- tert .butyl-bis( η 5 -cyclopentadienyl)]ZrCl 2 , space group P 2 1 2 1 2 1 , and meso( syn )-1,1′-[isopropylidene-3,3′-di- tert .butyl-bis( η 5 -cyclopentadienyl)]ZrCl 2 , space group P 2 1 / n .

Different coordination modes of a 1,1′,2,2′-ferrocenyltetraphosphine: bi- and tri-dentate behaviour with group 6 and 7 transition metals

The behaviour of 1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′-di(tert-butyl)ferrocene (1), acting as a homoannular or heteroannular ligand, has been studied. Due to the cisoid disposition of the phosphino groups of each ring, different coordination modes are observed. With group 6 metal carbonyls, M(CO)6, the tetraphosphine acts exclusively as a tridentate ligand. In contrast, the reaction with MnCp(CO)3 leads to complexes showing 1,1′ and 1,2 bidentate coordination modes. All these complexes have been characterised by 1H and 31P NMR spectroscopy. The molecular structures of the molybdenum complex [(1)Mo(CO)3] (2b) and the 1,1′ manganese complex [(1)MnCp(CO)] (3) have been established by X-ray diffraction.