Disilicon Complexes with Two Hexacoordinate Si Atoms: Paddlewheel-Shaped Isomers with (ClN4)SiSi(S4Cl) and (ClN2S2)SiSi(S2N2Cl) Skeletons.

The reaction of 1-methyl-3-trimethylsilylimidazoline-2-thione with hexachlorodisilane proceeds toward substitution of four of the disilane Cl atoms during the formation of disilicon complexes with two neighboring hexacoordinate Si atoms. The N, S-bidentate methimazolide moieties adopt a buttressing role, thus forming paddlewheel-shaped complexes of the type ClSi(μ-mt)4SiCl (mt=methimazolyl). Most interestingly, three isomers (i.e., with (ClN4)SiSi(S4Cl), (ClN3S)SiSi(S3NCl), and (ClN2S2)SiSi(S2N2Cl) skeletons as so-called (4,0), (3,1), and cis-(2,2) paddlewheels) were detected in solution by using 29Si NMR spectroscopic analysis. Two of these isomers could be isolated as crystalline solids, thus allowing their molecular structures to be analyzed by using X-ray diffraction studies. In accord with time-dependent NMR spectroscopy, computational analyses proved the cis-(2,2) isomer with a (ClN2S2)SiSi(S2N2Cl) skeleton to be the most stable. The compounds presented herein are the first examples of crystallographically evidenced disilicon complexes with two SiSi-bonded octahedrally coordinated Si atoms and representatives of the still scarcely explored class of Si coordination compounds with sulfur donor atoms. [ABSTRACT FROM AUTHOR]