Solid-state and solution structures of three lithiumsulfinimidamides: Identification of two distinct structural types

The bidentate sulfinimidamide ligand has almost the same bulk as the cyclopentadienyl l&and. Two distinct structural types of highly reactive lithium sulfinimidamides, commonly used reagents, have been identified by X-ray diffraction and solution NMR studies. In the crystalline state the diethyl ether adducts [(Me,SiN),S(C,H,)Li],.Et,O and [(Me,S~X’BuN)S(C,H,)Lil,.EtzO adopt a twisted tricyclic structure with both a four coordinate and a three coordinate lithium atom in the same aggregate. The ‘H NMR spectra at various temperatures and the low temperature phase-sensitive 6Li, ‘H HOEp. NMR experiment show that this structure is essentially retained in solution. The smaller bulk and higher polarity of tetrahydrofuran compared with diethyl ether results in the coordination of two solvent molecules to give [(Me,S~) S(C,H,)Li.THF],, which has a centrosymmetric stair-shaped tricyclic structure consisting of three fused four-membered rings.