Dehalogenation of Hexachlorocyclohexanes and Simultaneous Chlorination of Triethylsilane Catalyzed by Rhodium and Ruthenium Complexes

Complexes RhCl(PPh 3 ) 3 and RhH 2 Cl(P i Pr 3 ) 2 catalyze the dehalogenation of γ-hexachlorocyclohexane to benzene and the simultaneous chlorination of HSiEt 3 to ClSiEt 3 . In the presence of RhCl(PPh 3 ) 3, the dehalogenation is inhibited by addition of PPh 3 . 1 H and 31 P{ 1 H} NMR spectroscopy studies at variable temperature, on the behavior of the complex RhCl(PPh 3 ) 3 in the presence of γ-hexachlorocyclohexane and/or HSiEt 3, indicate that the catalytic reaction involves the initial interaction of the catalyst with the silane and that chloro−hydride intermediates related to RhH 2 Cl(PPh 3 ) 3 are the main species during the catalysis. The complexes RuHCl(PPh 3 ) 3, RuH 2 Cl 2 (P i Pr 3 ) 2, and RuHCl(η 2 -H 2 )(P i Pr 3 ) 2 also catalyze the dehalogenation of γ-hexachlorocyclohexane and the simultaneous chlorination of HSiEt 3 to ClSiEt 3 . In these cases, the dehalogenation products are 6/4 cyclohexene/cyclohexane (RuHCl(PPh 3 ) 3 ) and 4/6 cyclohexene/benzene (RuH 2 Cl 2 (P i Pr 3 ) 2 and RuHCl(η 2 -H 2 )(P i Pr 3 ) 2 ) mixtures. The dehalogenations of α- and δ-hexachlorocyclohexane catalyzed by RhCl(PPh 3 ) 3, RhH 2 Cl(P i Pr 3 ) 2, and RuHCl(PPh 3 ) 3 have been also investigated. The initial rates for the formation of ClSiEt 3 decrease in the sequence γ- > α- > δ-hexachlorocyclohexane.