SYNTHESIS AND CHARACTERIZATION OF NOVEL TYPES OF ADDUCTS OF NICKEL CARBONYL CLUSTERS WITH INDIUM HALIDES - X-RAY STRUCTURES OF [NET4]3[NI6(MU-3-INBR3)(ETA-2-MU-6-IN2BR5)(CO)11]CENTER-DOT-ME2CO, [NET4]4[NI6(ETA-2-MU-6-IN2BR5)2(CO)10]CENTER-DOT-ME2CO, AND [NET4]4[NI12(MU-6-IN)(ETA-2-MU-6-IN2BR4OH)(CO)22]

The reaction in tetrahydrofuran of InX3 (X = Cl, Br) with [Ni6(CO)12]2- up to a 2:1 molar ratio gives rise to several new carbonyl species, which probably consist of adducts of the InX3 Lewis acid with the [Ni6(CO)12]2- Lewis base. IR monitoring of the reaction allows one to distinguish the formation of at least three different compounds, which are respectively obtained with InX3/ [Ni6(CO)12]2- molar ratios of 0.5, 1.0, and 2.0. These suggested adducts could not be isolated and characterized owing to their lability in the miscellaneous organic solvents. However, while for X = Cl the main decomposition products were the parent [Ni6(CO)12]2-dianion and Ni(CO)4, the so far characterized transformation products for X = Br consist of [NEt4]3[Ni6(mu3-InBr3)(eta2-mu6-In2Br5)(CO)II], [NEt4]3[1], and NEt4]4-[Ni12(mu6-In)(eta2-mu6-In2Br4OH)(CO)22], [NEt4]4[3], salts. The former has been obtained in good yields (70-80% based on indium) from the suggested 2:1 InBr3:[Ni6(CO)12]2- adduct, whereas the latter resulted in low yields (10-20% based on indium) from the disproportionation of the corresponding 1:2 adduct during its working up. A third compound, namely [NEt4]4[Ni6(eta2-mu6-In2Br5)2(CO)10], [NEt4]4[2], has been isolated from the reaction of [1]3- with [Ni5(CO)12]2-. All the above compounds have been characterized by elemental analyses and single-crystal X-ray diffraction studies. [NEt4]3[1].Me2CO is orthorhombic, space group Pna2(1), with a = 30.196(8) angstrom, b = 13.469(7) angstrom, and c = 16.102(5) angstrom, [NEt4]4[2]-Me2CO is triclinic, space group P1, with a = 13.230(11) angstrom, b = 13.198(7) angstrom, c = 26.519(6) angstrom, alpha = 75.44(3)-degrees, beta = 88.69(4)-degrees, and gamma = 59.80(5)-degrees, and [NEt4]4[3] is monoclinic, space group P2(1)/c, with a = 14.896(2) angstrom, b = 42.194(8) angstrom, c = 14.075(3) angstrom, and beta = 110.32-degrees. The [1]3- trianion displays an octahedral Ni6 core capped on two adjacent faces by an In2Br5 moiety and on a third face, opposite to one of the above, by an InBr3 molecule. In the related [2]4-tetraanion there are present two In2Br5 moieties capping two opposite pairs of adjacent triangular faces of the Ni6 octahedron. In both anions, the remaining triangular faces of the octahedron are capped respectively by five and four face-bridging carbonyl groups, whereas each nickel atom binds a terminal carbonyl ligand. The structure of the [3]4-tetraanion derives from two distinct Ni6(CO)6(mu2-CO)5 moieties sandwiching a unique bare indium atom and bridged by an In2Br4(mu2-OH) moiety. The two Ni6(CO)6-(mu2-CO)5 fragments display different geometries. Thus, in one fragment the basic structure of the [Ni6(CO)12]2-dianion is retained even though an edge-bridging carbonyl group is replaced by a face-bridging indium atom. In contrast, the second fragment displays a fairly distorted metal framework which can be described as a square pyramid capped on a triangular face by the sixth Ni atom.