Ring opening of 1,2,3,4-tetramethyl-1,2,3,4-tetraphenylcyclotetrasilane in the presence of various transition metal catalysts has been studied. Pd and Pt compounds are most active. Compounds with bulky ligands [e.g., Pd(PPh(3))(4)] lead to the formation of "dimeric" cyclooctasilanes. Compounds with less bulky groups convert monomer to dimers and mixture of oligomers and polymers. Reactions with the all-trans monomer, tttt-(MePhSi)(4), result in the formation of stereoregular dimer, presumably all-trans, tttttttt-(MePhSi)(8), in high yields. Reactions in the presence of oxygen lead to the formation of polymers with inserted oxygen atoms in the main chain.