Long-range coupling in cyclic silanes

We report the synthesis of a mixed methyl- and hydro-substituted cyclosilane (1) possessing cis/trans stereoisomerism. Each diastereomer of 1 possesses distinct symmetry elements (cis-1: C-s-symmetric; trans-1: C-2-symmetric). Cyclosilane 1 is a model system to probe configuration- and conformation-dependent long-range proton-proton coupling. Extensive NMR spectroscopic characterization is reported, including one-dimensional H-1 NMR and Si-29 DEPT and INEPT+ spectra and two-dimensional H-1-Si-29 and H-1-H-1 correlated spectroscopy (HSQC, HMBC, COSY). On the basis of these experiments, molecular connectivity consistent with four-bond H-1-H-1 coupling is confirmed.