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 [H2SiAr2: Ar2 = C12H8O (1); Ar2 = C14H12O (2); Ar2 = C13H11N (3); Ar2 = C15H15N (4); Ar2 = C13H9Br2N (5)]. The reactivity of hydrosilanes 1−5 with (Ph3P)2Pt(η2-C2H4) (6) was investigated. At room temperature, mononuclear complexes, (Ph3P)2Pt(H)(SiAr2H) and (Ph3P)2Pt(SiAr2H)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, [(Ph3P)Pt(μ-η2-H-SiAr2)]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, [(Ph3P)Pt(μ-SiAr2)]3 (16), as the major product. However, reaction of 4 or 5 with complex 6 produced an unsymmetrical dinuclear complex, [(Ph3P)2Pt(H)(μ-SiAr2)(μ-η2-H-SiAr2)Pt(PPh3)] (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.