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

• Published in: Inorganic chemistry 2007-02, Vol.46 (3), p.652-659
• Main Authors: Weir, John J, McDonough, James E, Fortman, George, Isrow, Derek, Hoff, Carl D, Scott, Brian, Kubas, Gregory J
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic061654x

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 Å. 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 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)W(CO)4(PiPr3)2 which extrudes a •TePh radical.