A series of square-planar N, S-heterocyclic carbene (NSHC) complexes trans-[NiX2 (N- RBzTh) 2](BzTh= benzothiazolin-2-ylidene)(R/X= Bz/Br; Me/I; Et/I; Pri/I; Bui/I) have been synthesized and characterized by X-ray single-crystal diffraction analysis. These are the first crystallographically established NSHC complexes of nickel in the literature. The N, S- heterocyclic carbene (NSHC) rings invariably twist away from co-planarity with the metal ...