Nature of C→E and E→M Bonds in [NHC(R)→ER2→M(CO)5] Complexes

The heavy group 14 methylene analogues, EH2, (E = Ge and Sn) have been stabilized via efficient methods, thus enabling the chemistry of these novel inorganic hydrides to beexplored in depth [1]. The first stable transition-metal complex involving the heavy methylene congener,SnH2, as a ligand was synthesized by Rivard and his co-workers in2011 [1]. Also a theoretical study on some adducts of [NHC(CH3)→ER2] was reported by us in 2017. [2]. Herein a theoretical studies on structure and nature of the CE andE→M bonds in some [NHC(R)→ER2→M(CO)5]; (E=Ge,Sn,Pb)R=(CH3, H, F, Cl, Br)M=(Cr, Mo, W) complexes has been reported (Scheme.1). The structures of latter complexes are investigated at M06 /def2-SVP level of theory. The natures of CE and E→M bonds in the complexes are analyzed with NBO, EDA as well as ETS-NOCV at the mentioned level of theory. Results Show that changing E atom from Ge to Pb with considering the same R substituents and M atom, led to decreasing in the values of interaction energies between the NHC(R) and ER2M(CO)5 fragments in [NHC(R)→ER2→M(CO)5]; (E=Ge, Sn, Pb; R=CH3, H, F, Cl, Br; M=Cr, Mo, W) complexes. Results also confirm that the nature of E→M bond in the complexes studied is largely electrostatic with a contribution of about 50% in total interaction energies.