Synthesis and Solid-State Molecular Structure of Bi(silacyclohexyls) C5H10SiX-XSiC5H10 with X = H, Ph, F, Cl, Br and I

The synthesis and purification of novel bi(silacyclohexyls) C5H10SiX-XSiC5H10 with X = H (1), Ph (2), F (3), Cl (4), Br (5), and I (6), which are composed of two silacyclohexyl rings connected by a silicon–silicon single bond, is described. Molecular structures for 2, 4, 5, and 6 were determined employing X-ray crystallography. Surprisingly, the SiSi bond lengths increase in the order I < Br < Cl, contrary to what is observed for methylated disilanes Me2XSiSiXMe2. The bond lengthening can be traced back to 1, 3 nonbonded interactions between the halogen atoms and the axial hydrogen atoms in the SiC5 ring, which also cause a decrease of the SiSiX bond angles with increasing size of the halogen atom. Both rings substitute each other in the equatorial position for 4, 5, and 6, but in the axial position for 2.