Mixed Chloride/Amine Complexes of Dimolybdenum(II,II). 2. Reactions of Mo₂Cl₄(NHEt₂)₄with Monodentate and Bidentate Phosphines. New Type of Compounds Mo₂Cl₄(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.

Synthesis and Characterization of Osmium(II) Trispyrazolylborate Complexes

“…Transition metal complexes containing unidentate dmpm ligands are rare, but a few examples are known. ,− As is often the case for unidentate diphosphine complexes, the η 1 -dmpm compound 8 is a kinetic product. It is best prepared by stirring TpOs(PPh 3 ) 2 Cl with dmpm for several days at room temperature.…”

Peculiarities of Multiple Cr−Cr Bonding. Insights from the Analysis of Domain-Averaged Fermi Holes

“…Since its discovery in the 1960s, the phenomenon of metal−metal bonding has been the focus of continuous interest of experimental and theoretical studies. In addition to the new perspectives that the discovery of the molecules containing directly bonded metal atoms enriched the traditional paradigms of transition-metal chemistry, − another, apparently even more stimulating impetus for the development of this new field of chemistry came from the observation that not only can the corresponding bonds have the character of multiple bonds but also their multiplicities can exceed the usual limits known from organic chemistry. − Besides vigorous activity in the preparation and structural characterization of new compunds with unusual bond multiplicitites, the discovery of the phenomenon of metal−metal bonding has also immediately raised the challenge for the chemical theory to provide the background for elucidation of the nature of the underlying bonding interactions. The first successful model of multiple metal−metal bonding was suggested by Cotton, ,,, who related the existence of such bonds to interactions of incompletely filled shells of available d orbitals on the metals.…”

Reactivity of the labile complex [MoCl(η3-allyl)(CO)2(NCMe)2] with diphosphanes

“…The formation of 3 from 4 implies, besides chloride transfer between molybdenum centers, a change in the coordination mode of dmpm, a process that is known to be facile for this diphosphane. 8 Although slower than the formation of 3 from 4, 31 P NMR monitoring indicated that, in the presence of excess of dmpm, the binuclear complex 3 transforms into 2.…”