Synthesis, structure, and thermochemistry of the formation of the metal-metal bonded dimers [Mo(mu-TeAr)(CO)(3)((PP3)-P-i)](2) (Ar = phenyl, naphthyl) by phosphine elimination from Mo-center dot(TePh)(CO)(3)((PPr3)-Pr-i)(2)

摘要

The complexes ((TeAr)-Te-center dot)Mo(CO)(3)((PPr3)-Pr-i)(2) (Ar = phenyl, naphthyl; Pr-i = isopropyl) slowly eliminate (PPr3)-Pr-i at room temperature in a toluene solution to quantitatively form the dinuclear complexes [Mo(mu-TeAr)(CO)(3)((PPr3)-Pr-i)](2). The crystal structure of [Mo(mu-Te-naphthyl)(CO)(3)((PPr3)-Pr-i)](2) is reported and has a Mo-Mo distance of 3.2130 angstrom. The enthalpy of dimerization has been measured and is used to estimate a Mo-Mo bond strength on the order of 30 kcal mol(-1). Kinetic studies show the rate of formation of the dimeric chalcogen bridged complex is best fit by a rate law first order in ((TeAr)-Te-center dot)Mo(CO)(3)(P(i)Pr3)(2) and inhibited by added (PPr3)-Pr-i. The reaction is proposed to occur by initial dissociation of a phosphine ligand and not by radical recombination of 2 mol of ((TeAr)-Te-center dot)Mo(CO)(3)((PPr3)-Pr-i)(2). Reaction of ((TePh)-Te-center dot)Mo(CO)(3)((PPr3)-Pr-i)(2), with L = pyridine (py) or CO, is rapid and quantitative at room temperature to form PhTeTePh and Mo(L)(CO)(3)((PPr3)-Pr-i)(2), in keeping with thermochemical predictions. The rate of reaction of ((TeAr)-Te-center dot)W(CO)(3)((PPr3)-Pr-i)(2) and CO is first-order in the metal complex and is proposed to proceed by the associative formation of the 19 e(-) radical complex ((TePh)-Te-center dot)W(CO)(4)((PPr3)-Pr-i)(2) which extrudes a (TePh)-Te-center dot radical.