Organotransition-Metal Metallacarboranes. 46. Multidecker Sandwiches of the Cobalt Group Metals † ,1

The double-decker sandwich complex Cp*Ir(2,3-Et2C2B4H4) (1a) was prepared via deprotonation of nido-2,3-Et2C2B4H6 to its mono- or dianion and reaction with (Cp*IrCl2)2 in THF and isolated as a colorless air-stable solid; the B(4)-chloro derivative 1b was also obtained. Decapitation of 1a and 1b with TMEDA afforded colorless nido-Cp*Ir(2,3-Et2C2B3H5) (2a) and its 4-chloro derivative 2b. Chlorination of 1a by Cl2 or N-chlorosuccinimide gave the symmetrical species Cp*Ir(2,3-Et2C2B4H3-5-Cl) (1c), which was decapped to yield nido-Cp*Ir(2,3-Et2C2B3H4-5-Cl) (2c). The triple-decker complexes Cp*Ir(2,3-Et2C2B3H2-4[6]-Cl)IrCp* (3), an orange solid, and dark green Cp*Ir(2,3-Et2C2B3H2-4[6]-Cl)CoCp* (5) were prepared from 2a and nido-Cp*Co(2,3-Et2C2B3H5) (4a), respectively, by deprotonation and reaction with (Cp*IrCl2)2 in THF. Reaction of the 2c - anion with Rh(MeCN)3Cl3 gave the dark green tetradecker complex [Cp*Ir(Et2C2B3H2-5-Cl)]2RhH (6). In an attempt to prepare a heterotrimetallic Co−Rh−Ir tetradecker sandwich, a three-way reaction involving the deprotonated anions derived from Cp*Co(2,3-Et2C2B3H4-5-Cl) (4b) and 2c with Rh(MeCN)3Cl3 was conducted. The desired species Cp*Co(Et2C2B3H2Cl)RhH(Et2C2B3H2Cl)IrCp* (7) and the tetradeckers [Cp*Co(Et2C2B3H2Cl)]2RhH (8) and 6 were isolated in small quantities from the product mixture; many other apparent triple-decker and tetradecker products were detected via mass spectroscopy but were not characterized. All new compounds were isolated via column or plate chromatography and characterized via NMR, UV−visible, and mass spectroscopy and by X-ray crystal structure determinations of 1a and 3. Crystal data for 1a: space group C2/c; a = 28.890(5) Å, b = 8.511(2) Å, c = 15.698(4) Å, β = 107.61(2)°; Z = 8; R = 0.049 for 1404 independent reflections having I > 3σ(I). Crystal data for 3: space group P21/c; a = 11.775(4) Å, b = 15.546(5) Å, c = 15.500(5) Å, β = 103.16(3)°; Z = 4; R = 0.066 for 2635 independent reflections having I > 3σ(I).