Dinuclear Tin(II) Complex of a Bulky cis-Oxamide: Synthesis, Characterization, Crystal Structure, and DFT Studies

The reaction of the di-lithiated oxamide of 1 with two equivalents of SnCl2 provided the tin trans-oxamide 3. In solution, spectroscopic analysis suggests exclusively the formation of a trans-oxamide (trans-3). However, the solid state shows an atypical cis-oxamide (cis-3), where the oxamide fragment acts as an anti-Janus head ligand. An 119Sn-NMR variable temperature experiment ([D8]THF) of the trans-oxamide (trans-3) was performed however, at lower temperature no additional signal was observed, which confirmed the absence of a dynamic equilibrium. Dispersion-corrected density functional calculations revealed that the cis conformation of this tin(II) oxamide complex is more stable than the trans isomer by 1.4 kcal center dot mol1.