Heterometalation of 1,1'-Bis( ortho-carborane)

Deboronation of [8-(1'- closo-1',2'-C₂B₁₀H₁₁)- closo-2,1,8-MC₂B₉H₁₀] affords diastereoisomeric mixtures of [8-(7'- nido-7',8'-C₂B₉H₁₁)- closo-2,1,8-MC₂B₉H₁₀]^- anions (1, M = Ru( p-cymene); 2, M = CoCp) isolated as [HNMe₃]⁺ salts. Deprotonation of 1 and reaction with CoCl₂/NaCp followed by oxidation yields [8-(1'-3'-Cp -closo-3',1',2'-CoC₂B₉H₁₀)-2-( p-cymene)- closo-2,1,8-RuC₂B₉H₁₀] isolated as two separable diastereoisomers, namely, 3α and 3β, the first examples of heterometalated derivatives of 1,1'-bis( ortho-carborane). Deprotonation of [7-(1'- closo-1',2'-C₂B₁₀H₁₁)- nido-7,8-C₂B₉H₁₁]^-, metalation with CoCl₂/NaCp* and oxidation affords the isomers [1-(1'- closo-1',2'-C₂B₁₀H₁₁)-3-Cp*- closo-3,1,2-CoC₂B₉H₁₀] (4) and [8-(1'- closo-1',2'-C₂B₁₀H₁₁)-2-Cp*- closo-2,1,8-CoC₂B₉H₁₀] (5) as well as a trace amount of the 13-vertex/12-vertex species [12-(1'- closo-1',2'-C₂B₁₀H₁₁)-4,5-Cp*₂- closo-4,5,1,12-Co₂C₂B₉H₁₀] (6). Reduction then reoxidation of 4 converts it to 5. Deboronation of either 4 or 5 yields a diastereoisomeric mixture of [8-(7'- nido-7',8'-C₂B₉H₁₁)-2-Cp*- closo-2,1,8-CoC₂B₉H₁₀]^- (7), again isolated as the [HNMe₃]⁺ salt. Deprotonation of this followed by treatment with [RuCl₂( p-cymene)]₂ produces [8-(1'-3'-( p-cymene)- closo-3',1',2'-RuC₂B₉H₁₀)-2-Cp*- closo-2,1,8-CoC₂B₉H₁₀] (8) as a mixture of two diastereoisomers in a 2:1 ratio, which could not be separated. Diastereoisomers 8 are complementary to 3α and 3β in which {CoCp} and {Ru( p-cymene)} in 3 were replaced by {Ru( p-cymene)} and {CoCp*}, respectively, in 8. Finally, thermolysis of mixture 8 in refluxing dimethoxyethane yields [8-(8'-2'-( p-cymene)- closo-2',1',8'-RuC₂B₉H₁₀)-2-Cp*- closo-2,1,8-CoC₂B₉H₁₀] (9), again as a 2:1 diastereoisomeric mixture that could not be separated. All new species were characterized by multinuclear NMR spectroscopy, and 3α, 3β, 4, 5, 6, and 9 were also characterized crystallographically.