KCS

Recently, developing new catalysts with high economic advantages using 1st row transition metals are  drawing attention. Such 1st row transition metal complexes are not widely used in industry due to their limited applications, even though they are inexpensive and abundant. Controlling the properties of 1st row metals to mimic the intrinsic character of the frontier orbitals of heavy 2nd and 3rd row metals would expand its utility. Metal-ligand cooperation (MLC) has been employed as a new synthetic methodology to tune the chemical properties of the light transition metals. In this study, we synthesized a series of new bismuth-nickel pincer complexes supported by tetradentate ligand (BiP3) to explore the reactivity of the Bi–Ni site. From a BiP3 ligand, the oxidative-addition of a Bi–C bond at nickel(0) species gave a distorted trigonal bipyramidal nickel(Ⅱ) complex, (BiP)2Ni(PPh). In the reaction with MeI, the nickel(Ⅱ) complex also showed the oxiative-addition product, (BiP2Me)Ni(I)(PPh), where methylation occurs at the Bi site and nickel gets oxidized by 2-electrons. Subsequent exposure to UV-irradiation resulted in the four-coordinate reduction product, (BiP2)Ni(I), possessing highly distorted square planar geometry with a shortened Bi–Ni bond length compared to that of (BiP)2Ni(PPh). As an alternate way to prepare a metal-halide complex, HCl was directly reacted with (BiP)2Ni(PPh) to give (BiP2)NiCl. It was previously reported that tBuNC could facilitate migration of the nickel-bound moiety to the central phosphide moiety of a PP2 ligand. Accordingly, we treated (BiP2)NiCl with tert-butyl isocyanide, resulting in the formation of a trigonal bipyramidal species, {(BiP2)Ni(tBuNC)2}{Cl}. Interestingly, the chloride anion weakly interacts with bismuth, showing an unprecedently long Bi–Cl bond length of 3.16 Å, resulting in the elongation of the Bi–Ni bond. The resulting product, [(BiP2)Ni(tBuNC)2][BPh4], was synthesized by the addition of NaBPh4 to the {(BiP2)Ni(tBuNC)2}{Cl}. The product showed a shorter Bi–Ni bond length, 2.617(1) Å, than that of the starting material. This work provides information on the bonding character of two metal sites, bismuth and nickel, as well as the reactions which occur in a heterobimetallic cooperative way.