Synthesis of nickel-monocarbollide complexes by oxidative insertion.

Treatment of the 11-vertex carborane anion [closo-2-CB10H11]- with Ni(0) reagents in tetrahydrofuran (THF) affordsvia oxidative insertion reactions12-vertex Ni(II) complexes, isolated as the salts [N(PPh3)2][2,2-L2-closo-2,1-NiCB10H11] (L = CO (1a), CNBut (1b), and CNXyl (1c; Xyl = C6H3Me2-2,6); L2 = cod (1d; cod = 1,2:5,6-η-cyclo-octa-1,5-diene)). One CO ligand in 1a is readily replaced by donors L‘ in the presence of Me3NO to give the species [N(PPh3)2][2-CO-2-L‘-closo-2,1-NiCB10H11] (L‘ = PEt3 (1e), PPh3 (1f), CNBut (1g), and CNXyl (1h)). The anionic complexes themselves readily react with hydride abstracting reagents in the presence of donor ligands to yield zwitterionic complexes in which boron vertexes bear substituents that are bound through C, N, or O atoms. Thus, for example, 1c with H+ and CNXyl gives [2,2,7-(CNXyl)3-closo-2,1-NiCB10H10] (2b), while 1f with Me+ in the presence of OEt2 affords [2-CO-2,11-{μ-PPh2(C6H4-o)}-7-OEt2-closo-2,1-NiCB10H9] (4), in which an additional cycloboronation of on...