cyclohexanediol) are dimeric, Ph(2)Si(AnErytH(-2)) (3) is monomeric, and Ph(2)Si(L-AnThreH(-2)) (4; AnThre = anhydrothreitol) is trimeric both in the solid state and in solution. Ph(2)Si(cis-CptdH(-2)) (5) (Cptd = cyclopentanediol) is monomeric in solution but dimerizes on crystallization. Si(AnErytH(-2))(2) (6) and Si(cis-CptdH(-2))(2) (7) are monomeric spiro compounds in solution but are pentacoordinate dimers