Synthesis, Structure, and Thermochemistry of the Formation of the Metal−Metal Bonded Dimers [Mo(μ-TeAr)(CO)3(PiP3)]2 (Ar = Phenyl, Naphthyl) by Phosphine Elimination from •Mo(TePh)(CO)3(PiPr3)2

The complexes (•TeAr)Mo(CO)3(PiPr3)2 (Ar = phenyl, naphthyl; iPr = isopropyl) slowly eliminate PiPr3 at room temperature in a toluene solution to quantitatively form the dinuclear complexes [Mo(μ-TeAr)(CO)3(PiPr3)]2. The crystal structure of [Mo(μ-Te−naphthyl)(CO)3(PiPr3)]2 is reported and has a Mo−Mo distance of 3.2130 A. 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)Mo(CO)3(PiPr3)2 and inhibited by added PiPr3. The reaction is proposed to occur by initial dissociation of a phosphine ligand and not by radical recombination of 2 mol of (•TeAr)Mo(CO)3(PiPr3)2. Reaction of (•TePh)Mo(CO)3(PiPr3)2, with L = pyridine (py) or CO, is rapid and quantitative at room temperature to form PhTeTePh and Mo(L)(CO)3(PiPr3)2, in keeping with thermochemical predictions. The rate of reaction of (•TeAr)W(CO)3(PiPr3)2 a...