Arene-Metal-Carborane Triple-Decker Sandwiches. Designed Synthesis of Homo- and Heterobimetallic Complexes of Cobalt, Iron, Ruthenium, and Osmium

Article abstract of DOI:10.1021/ja00195a034

This paper describes the systematic preparation and characterization of new families of triple-decker sandwich complexes incorporating formal cyclo-Et2C2B3H3(4-) bridging ligands, including the first species of this class containing second- or third-row transition metals.Complexes of general formula (L)M(Et2C2B3H3)M'(L) (M = Ru, Os; M' = Co, Ru; L = cymene , Cp, or C5Me5) were obtained in stepwise fashion via (1) synthesis of closo-(L)M(Et2C2B4H4) metallacarboranes, (2) decapitation (apex BH removal) of these complexes to give nido-(L)M(Et2C2B3H5), (3) bridge deprotonation to form the corresponding mono- or dianion, and (4) reaction of the anion with an arene metal halide to generate the desired triple-decker compound.In addition, the cobalt-iron triple-decker CpCo(Et2C2B3H3)FeCp was prepared via treatment of (η⁶-C8H10)Fe(Et2C2B3H4)(1-) with Na(1+)Cp(1-) and CoCl2 followed by air oxidation.The reaction of (CO)3RuCl2 with (C5Me5)Co(Et2C2B3H3)(2-) gave the pseudo-triple-decker complex (C5Me5)Co(Et2C2B3H3)Ru(CO)3.The triple-deckers, especially those containing osmium, are susceptible to chlorination by RuCl3, OsCl3, or dichloromethane, forming exclusively the 4-chloro derivatives.All of the characterized triple-decker complexes are air-stable crystalline solids (except for the osmium-ruthenium species, which are air sensitive) and have been structurally characterized from their (11)B and (1)H NMR, infrared, visible-UV, and unit- and high-resolution mass spectra, further supported by X-ray crystallographic analyses of (cymene)Ru(Et2C2B3H3)Ru(cymene) (10) and CpCo(Et2C2B3H3)Ru(cymene) (11a).Crystal data for 10: mol wt 561.13; space group PI; Z = 2; a = 10.409(3), b = 11.268(5), c = 12.002(4) Angstroem; α = 96.16(3), β = 99.49(2), γ = 106.69(3) deg; V = 1312(2) Angstroem³; R = 0.043 for 4777 reflections having F₀² > 3?(F₀²).Crystal data for 11a: mol wt 476.92; space group P2₁/c; Z = 4; a = 8.808(6), b = 17.708(8), c = 14.194(8) Angstroem; β = 103.50(4) deg; V = 2153(4) Angstroem³; R = 0.058 for 3289 reflections having F₀² > 3?(F₀²).