Si−H Bond Activation by (Ph₃P)₂Pt(η²-C₂H₄) in Dihydrosilicon Tricycles that Also Contain O and N Heteroatoms

Abstract

Several tricyclic phenoxasilin and phenazasiline heterocycles were synthesized from the corresponding 2,2‘-dilithio-diphenyl ether or diphenyl amine precursor and silicon tetrachloride (or trichlorosilane) followed by reduction with lithium aluminum hydride [H 2 SiAr 2: Ar 2 = C 12 H 8 O ( 1 ); Ar 2 = C 14 H 12 O ( 2 ); Ar 2 = C 13 H 11 N ( 3 ); Ar 2 = C 15 H 15 N ( 4 ); Ar 2 = C 13 H 9 Br 2 N ( 5 )]. The reactivity of hydrosilanes 1 − 5 with (Ph 3 P) 2 Pt(η 2 -C 2 H 4 ) ( 6 ) was investigated. At room temperature, mononuclear complexes, (Ph 3 P) 2 Pt(H)(SiAr 2 H) and (Ph 3 P) 2 Pt(SiAr 2 H) 2, were generally observed by NMR spectroscopy but were too reactive or unstable to isolate. Dinuclear and in some cases trinuclear Pt−Si-containing complexes were observed as the major products from the reactions. Symmetrical dinuclear complexes, [(Ph 3 P)Pt(μ-η 2 -H-SiAr 2 )] 2 ( 8 and 22, respectively), were produced from the reaction of 1 or 3 with 6 . In contrast, reaction of silane 2 with 6 produced a trinuclear complex, [(Ph 3 P)Pt(μ-SiAr 2 )] 3 ( 16 ), as the major product. However, reaction of 4 or 5 with complex 6 produced an unsymmetrical dinuclear complex, [(Ph 3 P) 2 Pt(H)(μ-SiAr 2 )(μ-η 2 -H-SiAr 2 )Pt(PPh 3 )] ( 26 and 30, respectively), as the major component. The molecular structures of a symmetrical ( 22 ) and unsymmetrical dinuclear ( 30 ) complex as well as a trinuclear ( 16 ) complex were determined by X-ray crystallography.