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 [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.