Inorganic Chemistry, Vol.36, No.17, 3602-3608, 1997
Apically linked small metallacarborane clusters. Directed synthesis and structural characterization of 7,7'-[Cp*Co(2,3-Et2C2B4H3)](2) and [Cp*Co(2,3-Et2C2B4H3-7)](2)X complexes (X=MeCH, HC=CH, C C)
A series of novel bis(cobaltacarboranyl) (CoC2B4)(2)X dicluster complexes whose B(7) (apex) atoms are linked by organic moieties involving sp-, sp(2)-, or sp(3)-hybridized carbon, or by a direct B(7)-B(7') bond, has been prepared by extension of the recently described ''recapitation'' method (Curtis, M. A.; et al. Inorg. Chem. 1996, 35, 6703) that entails treatment of 6-vertex nido-CoC2B3 dianions with monoboron reagents. Reactions of Li-2[nido-Cp*Co-(Et2C2B3H3)] in toluene with MeCH(BCl2)(2) and with cis-(BCl2)C2H2 gave, respectively, [Cp*Co(2,3-Et2C2B4H3-7-)](2)MeCH (5) and cis-[Cp*Co(2,3-Et2C2B4H3-7-)](2)C2H2 (6a) following chromatographic separation. Ultraviolet irradiation of 6a induced partial conversion to the trans isomer 6b, affording a 46:54 trans/cis equilibrium mixture in 84 h. Reactions of the same cobaltacarborane dianion with bis(catecholboryl)acetylene and with bis(catecholdiboryl) gave [Cp*Co(2,3-Et2C2B4H3-7-)](2)C-2 (7) and [Cp*Co(2,3-Et2C2B4H3-7-)](2) (8), respectively. The new complexes were isolated as air-stable, crystalline orange solids and were characterized from their H-1. B-11, and C-13 NMR, IR, UV-visible, and mass spectra, supported by X-ray crystallographic studies of 5, 6a, 7, and 8. Crystal data for 5: space group P2(1)ca (orthorhombic); a = 14.220(10) Angstrom, b = 15.690(10) Angstrom, c = 16.860(10) Angstrom, Z = 4; R = 0.041 for 7485 independent reflections. Crystal data for 6a: space group C2/c (monoclinic); a 12.849(6) Angstrom, b = 11.435(6) Angstrom, c = 25.619(13) Angstrom, beta = 96.230(10)degrees; Z = 4; R = 0.036 for 5440 independent reflections. Crystal data for 7: space group P2(1)/n (monoclinic); a = 17.298(12) Angstrom, b = 13.932(10) Angstrom, c = 30.82(2) Angstrom, beta = 96.34(5)degrees; Z = 8; R = 0.070 for 9632 independent reflections. Crystal data for 8: space group P (1) over bar (triclinic); a = 9.150(10) Angstrom, b = 10.270(10) Angstrom, c = 10.340(10) Angstrom, alpha = 84.52(5)degrees, beta = 78.05(5)degrees, gamma = 68.6(5)degrees; Z = 1; R = 0.056 for 5154 independent reflections.