Toward a More Detailed Understanding of Oxidative-Addition Mechanisms: Combined Experimental and Quantum-Chemical Study of the Insertion of Titanium Atoms into C−H, Si−H, and Sn−H Bonds

Abstract

The reactions between Ti atoms and CH 4 , SiH 4 , and SnH 4 at a temperature of 12 K in Ar matrixes were studied experimentally by IR spectroscopy, taking in the effect of isotopic substitution, and by quantum-chemical calculations. The experiments show that the reactivity changes considerably from CH 4 to SiH 4 or SnH 4 . The reaction between Ti and CH 4 proceeds inefficiently, and only after photolytic activation of the Ti atoms does insertion occur to give HTiCH 3 , which features only terminal Ti-H and C-H bonds. On the other hand, reactions with SiH 4 and SnH 4 occur upon deposition, leading to the products cis- and trans-HTi(μ-H) 2 SiH and HTi(μ-H) 3 E (E = Si, Sn). Selective photolysis can be used to increase the yields of these products. In agreement with the experimental results, quantum-chemical calculations predict the lowest energy form of a molecule with the overall formula TiEH 4 to be HTiCH 3 with only terminal H atoms for E = C but HTi(μ-H) 3 E with three bridging H atoms in the case of E = Si, Sn.