Unprecedented coordination of dithiocarbimate in multinuclear and heteroleptic complexes

An uncommon coordination protocol induced by the p-tolylsulfonyl dithiocarbimate ligand (L) [L = p-CH3C6H4SO2N CS22-] in conjunction with PPh3 allowed the formation of novel homodimetallic, Cu-2(PPh3)(4)L (1), trinuclear heterometallic Cu2Ni(L)(2)(PPh3)(4) (2) and heteroleptic complexes of general formula cis-[M(PPh3)(2)L] [M = Pd(II) (3), Pt(II) (4)]. The complexes have been characterized by microanalysis, mass spectrometry, IR, H-1, C-13 and P-31 NMR and electronic absorption spectra and single-crystal X-ray crystallography. 2 uniquely consists of square planar, trigonal planar and tetrahedral coordination spheres within the same molecule. In both heteroleptic complexes 3 and 4 the orientation of aromatic protons of PPh3 ligand towards the Pd(II) and Pt(II) center reveals C-H center dot center dot center dot Pd and C-H center dot center dot center dot Pt rare intramolecular anagostic or preagostic interactions. These complexes exhibit photoluminescent properties in solution at room temperature arising mainly from intraligand charge transfer (ILCT) transitions. The assignment of electronic absorption bands has been corroborated by time dependent density functional theory (TD-DFT) calculations. Complexes 1 and 2 with sigma(rt) values similar to 10(-6) S cm(-1) show semi-conductor properties in the temperature range 313-403 K whereas 3 and 4 exhibit insulating behaviour.