Synthesis, Reactivity, and Structural Transformation of Mono- and Binuclear Carboranylamidinate-Based 3d Metal Complexes and Metallacarborane Derivatives

A series of carboranylamidinate-based 3d metal complexes are reported. Treatments of 3d metal dichlorides (CoCl₂, NiCl₂(DME), CuCl₂) with the lithium salts of carboranylamidines (Cab^<i>N</i>H) generate the mononuclear C,N-coordinated complexes [(RNC­(<i>closo</i>-1,2-C₂B₁₀H₁₀)­(NHR)]₂M (<b>1</b>–<b>6</b>; M  Co, Ni, Cu; R = <i>i</i>Pr, Cy) in moderate yields, respectively. These complexes have similar structures in the solid state, in which the metal atom is coordinated to two nitrogen atoms and bonded to two cage carbon atoms in a distorted-tetrahedral geometry. As a noninnocent ligand, Cab^<i>N</i>H can be modified to produce carboranylamidinate thiol (Cab^<i>N</i>SH) and nido derivatives Dcab^<i>N</i>H (<b>9</b>, <b>10</b>), respectively. Reaction of cupric acetate with 1 equiv of Cab^<i>N</i>SH gave the binuclear complexes {[RNC­(<i>closo</i>-1,2-C₂B₁₀H₁₀)­(NHR)]­SCu}₂ (R = <i>i</i>Pr (<b>7</b>), Cy (<b>8</b>)) in 66 and 63% yields, respectively. The structure of <b>7</b> shows the formation of a Cu–Cu bond, and the geometry of the Cu₂S₂ core is planar. The zwitterionic nickel dicarbollide complexes (Dcab^<i>N</i>)­Ni­(PPh₃)Cl (<b>11</b>, <b>12</b>) were prepared by reactions of the lithium salts of Dcab^<i>N</i>H (<b>9</b>, <b>10</b>) with NiCl₂(PPh₃)₂ in THF. All complexes were characterized by elemental analysis and IR and NMR spectroscopy. The structures of <b>1</b>, <b>3</b>–<b>5</b>, <b>7</b>, and <b>9</b>–<b>11</b> were further confirmed by single-crystal X-ray diffraction