Reactivity of hemilabile 2-pyridylselenolate ligand towards [NiCl2(dppe)]: Combined experimental and theoretical study

Abstract

A series of nickel complexes of varied nuclearity and geometrical diversity have been synthesized by the choice of equivalent ratio of [NiCl2(dppe)] (dppe=1,2-Bis(diphenylphosphino)ethane) and hemilabile pyridylselenolate ligand. In a substitution reaction of [NiCl2(dppe)] with one equivalent of NaSeC5H4N, a complex of composition [Ni(Cl)(SeC5H4N)(dppe)] was formed which on further treatment with sodium tetra-phenylborate afforded chelated compound of composition [Ni(κ2-SeC5H4N)(dppe)]BPh4. However, the same reaction with two equivalent of 2-pyridylselenolate resulted cis configured mononuclear compound [Ni(SeC5H4N)2(dppe)]. The latter complex on reaction with another mole of [NiCl2(dppe)] yielded a binuclear complex [Ni2(μ-SeC5H4N)2(dppe)2]2+which upon re-crystallization in dichloromethane solution resulted in trinuclear product [Ni3(μ-Se)2(dppe)2]2+. This selenido bridged cluster complex has also been obtained through the reaction of three mole [NiCl2(dppe)] with two mole of NaSeC5H4N. All the complexes were characterized by elemental analysis, UV–vis, IR, and NMR (1H, 31P{1H} and 77Se{1H}) spectroscopy. The molecular structures of [Ni(κ2-SeC5H4N)(dppe)](BPh4) and [Ni3(μ-Se)2(dppe)2](BPh4)2 were established by single crystal X-ray diffraction analysis. In order to get better insight, reactivity of nickel towards hemilabile ligand has also been compared with their Pd counterpart with the help of DFT studies.