Cyclotetrasiloxanetetrols with Methyl Groups at Silicon: Isomers <i>all-cis</i>- and <i>cis-trans-cis-</i>[MeSi(O)OH]₄

1,3,5,7-Tetramethyl-1,3,5,7-tetrahydroxycyclotetrasiloxane has been synthesized in good yield from tetrapotassium tetramethylcyclotetrasiloxanolate. Methods for isolation of all-cis-isomer I and cis-trans-cis-isomer II as the only crystalline product have been developed. Both isomers have been characterized by single-crystal X-ray diffraction analysis (XRD), elemental analysis, NMR (1H, 13C, 29Si), and IR. The stability of these compounds in solutions and the solid state has been investigated.