CHEMISTRY OF C-TRIMETHYLSILYL-SUBSTITUTED HETEROCARBORANES .12. SYNTHETIC, STRUCTURAL, AND BONDING STUDIES ON THE CARBONS APART-NICKELACARBORANES CLOSO-NICKELACARBORANES AND COMMO-NICKELACARBORANES DERIVED FROM CARBONS ADJACENT CLOSO-CARBORANE 1,2-(SIME3)2-1,2-C2B4H4

The reaction of ''carbons adjacent'' closo-1,2-(SiMe3)2-1,2-C2B4H4 Wit h lithium naphthalide in THF produces the ''carbons apart- dilithium c ompound u-H)2Li(THF)](mu-THF)-1-Li-2,4-(SiMe3)2-2,4-C2B4H4 (I), that e xists as discrete dimers in the solid state. However, when the reactio n was carried out in TMEDA, the monomeric carbons apart dilithiacarbor ane -H)2Li(TMEDA)]-1-Li(TMEDA)-2,4-(SiMe3)2-2,4-C2B4H4 (II) was isolat ed in 90% yield. The H-1, Li-7, B-11, and C-13 NMR spectra and IR spec tra of I and II are all consistent with their molecular formulas. The reaction of the THF-solvated dilithium compound, I, with anhydrous NiC l2 in a 1:1 molar ratio, in a 1:1 mixture of n-hexane and THF, produce d the carbons apart nickel sandwich commo-1,1'-Ni[2,4-(SiMe3)2-2,4-C2B 4H4]2 (III), along with elemental nickel (Ni0). On the other hand, a T MEDA-complexed species, closo-1-Ni(TMEDA)-2,4-(SiMe3)2-2,4-C2B4H4 (IV) , was isolated from the analogous reaction of NiCl2 with the TMEDA-sol vated dilithium compound, II. The nickelacarboranes were also characte rized by H-1, B-11, and C-13 NMR spectra, IR and mass spectra, and ele mental analyses. The molecular structures of I-IV were determined by X -ray diffraction. The closo-nickelacarborane (IV), a formal Ni(II) hal f-sandwich, was also produced in a redox reaction involving commo-Ni(I V) sandwich III in wet TMEDA at room temperature. While the closo-dili thium compounds, I and II, crystallized in the monoclinic space group P2(1)/n, the commo-nickelacarborane (III) and closo-nickelacarborane ( IV) crystallized in orthorhombic and monoclinic space groups Pbcn and P2(1)/n, respectively, with a = 11.353(5), 9.828(4), 12.409(3), and 8. 310 (2) angstrom, b = 17.490(7), 22.267(7), 18.436(5), and 19.657(4) a ngstrom, c = 13.273(6), 15.064(5), 12.976(3), and 14.655(3) angstrom, beta = 104.33(3), 95.87(3), 90.00, and 94.14(2)degrees, V = 2551(2), 3 279(2), 2969(1), and 2387.6(9) angstrom3, and Z = 2, 4, 4, and 4. The final refinements of I-IV converged at R = 0.076, 0.060, 0.033, and 0. 041 and R(w) = 0.095, 0.064, 0.040, and 0.052, respectively.