Si-H bond activation by (Ph3P)2Pt(η2-C2H4) in dihydrosilicon tricycles that also contain O and N heteroatoms

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