The new enneanuclear nickel carbonyl anion [Ni9(CO)16]2− and its relationships with the [Ni12(CO)21]4− and [Ni6Rh3(CO)17]3− clusters

The reaction of [N(PPh3)2]2[Ni6(CO)12] with Cu(PPh3)xCl (x=1, 2), as well as the degradation of [N(PPh3)2]2[H2Ni12(CO)21] with PPh3, affords the new and unstable dark orange–brown [N(PPh3)2]2[Ni9(CO)16].THF salt in low yields. This salt has been characterized by a CCD X-ray diffraction determination, along with IR spectroscopy and elemental analysis. The close-packed two-layer metal core geometry of the [Ni9(CO)16]2− dianion is directly related to that of the bimetallic [Ni6Rh3(CO)17]3− trianion and may be envisioned to be formally derived from the hcp three-layer geometry of [Ni12(CO)21]4− by the substitution of one of the two outer [Ni3(CO)3(μ−CO)3]2− layers with a face-bridging carbonyl group.