ORGANOSUBSTITUTED SILOLES BY 2 FOLD ORGANOBORATION OF DI-1-ALKYNYLSILANES

Me2Si(C=CR)2 [R = Me (A), Bu (B), tBu (C), iPent (D), Ph (E), Me3Si(F)], prepared from Me2SiCl2 and MC = CR (M = Li, Na, K), react with Et3B by 1,1-ethyloboration to form the organo-substituted siloles Me2SiC(R) = C(BEt2)C(Et) = CR (1a-f) in high yields with different reaction rates: F > B almost-equal-to D > A > C > E. Me2Si(C = CiPent)(C = CPh) (H) and Et3B give a 5:1 mixture of the two regioisomeric substituted siloles 2 and 2'. -1a and e are deborylated with H2NCH2CH2OH or MeCO2H to 3a and e, respectively. 1a reacts with maleic anhydride to yield the [4+2] addition compound 4a. With (OC)5Fe, CpCo(C2H4)2, and (CDT)Ni the cycloracemic (ligand)transition metal eta4-complexes [(OC)3Fe-1a (5a), (OC)3Fe-3a (6a), CpCo-3a(7a)] and the cyclodiastereomeric eta4, eta4-complexes Ni-(3a)2 (8a/8a') are formed. All products were characterized by multinuclear NMR, including measurements of (J(SiC)-Si-29-C-13) and (J(CC)-C-13-C-13).