title: Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo(2)Cl(4)(NHEt(2))(4) with Monodentate and Bidentate Phosphines. New Type of Compounds Mo(2)Cl(4)(diphosphine)(4).
abstract: The complex Mo(2)Cl(4)(NHEt(2))(4) (1) undergoes facile substitution reactions of the amine ligands by phosphines to give compounds with the same core structure, Mo(2)Cl(4)(phosphine)(4), where the phosphine is PMe(3) (2), PMe(2)Ph (3), PHEt(2) (4), dmpm (bis(dimethylphosphino)methane) (5), or dmpe (1,2-bis(dimethylphosphino)ethane) (6). Complexes of the type M(2)X(4)L(4) are well-known with monodentate ligands, but there is no previous crystallographically verified example of the M(2)X(4)L(4) type of compound in which L is a potentially bidentate ligand acting as a unidentate ligand. Mo(2)Cl(4)(eta(1)-dmpm)(4) (5) can be isolated in good yield as the kinetic product of the substitution reaction at room temperature. When a solution of 5 in THF is heated, transformation into the more stable compound Mo(2)Cl(4)(&mgr;-dmpm)(2) (7) takes place. Mo(2)Cl(4)(eta(1)-dmpe)(4) (6) is stable in solution in the presence of free phosphine and can be detected by NMR. Over time it converts to a polymeric material which precipitates from the solution. For dppm (bis(diphenylphosphino)methane) (8) and dppa (bis(diphenylphosphino)amine) (9), only products of the stoichiometry Mo(2)Cl(4)(diphosphine)(2) were obtained. The crystal structures of the complexes 4 and 5 have been investigated by X-ray diffraction. The crystallographic parameters for them are as follows: for 4, orthorhombic space group Pbcn with a = 7. 6015(8) Å, b = 20.120(8) Å, c = 19.070(6) Å, and Z = 4; for 5, hexagonal space group P6(4)22 with a = 12.396(1) Å, c = 21.960(2) Å, and Z = 3. Both structures have a Mo(2)Cl(4)P(4) core where the phosphorus atoms are trans one to another on each metal center. The Mo-Mo distances of 2.137(1) Å (4) and 2.137(1) Å (5) are consistent with quadruple bonding.
authors.affiliation: Department of Chemistry and Laboratory for Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012.
authors.forename: F. Albert
authors.initials: FA
authors.lastname: Cotton
authors.forename: Evgeny V.
authors.initials: EV
authors.lastname: Dikarev
authors.forename: Santiago
authors.initials: S
authors.lastname: Herrero