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Abstract

In a single step, from [Cp*RuCl2]2 (Cp* = η5-C5Me5) and Li[BH4], nido-1,2-(Cp*Ru)2(μ-H)2B3H7, 1, is produced in high yield. Addition of BH3·THF to 1 results in conversion to nido-1,2-(Cp*Ru)2(μ-H)B4H9, 2. Reaction of BH3·THF directly with [Cp*RuCl2]2 yields a mixture of 1 and 2. In two steps, a rhodium analogue, nido-2,3-(Cp*Rh)2B3H7, 9, is accessible by the reaction of [Cp*RhCl2]2 and Li[BH4] to exclusively produce (Cp*Rh)2B2H6, 8, which adds BH3·THF to give 9 as the major product in a mixture. Reaction of BH3·THF directly with [Cp*RhCl2]2 yields the chloro derivative of 9, nido-1-Cl-2,3-(Cp*Rh)2B3H6, 11, in high yield via the intermediate positional isomer, nido-3-Cl-1,2-(Cp*Rh)2B3H6, 10. With high concentrations of Co2(CO)8, 1 reacts with Co2(CO)8 to give nido-1-(Cp*Ru)-2-(Cp*RuCO)-3-Co(CO)2(μ3-CO)B3H6, 3, whereas low concentrations permit competitive degradation of 1 to yield arachno-(Cp*Ru)(CO)(μ-H)B3H7, 4. On the other hand, reaction of 11 with Co2(CO)8 gives closo-1-Cl-6-{Co(CO)2}-2,3-(Cp*Rh)2(μ3-CO)B3H3, 12. Mild thermolysis of 3 results in loss of hydrogen and the formation of closo-6-Co(CO)2-2,3-(Cp*Ru)2(μ-CO)(μ3-CO)B3H4, 5, whereas thermolysis of 2 results in loss of hydrogen and formation of pileo-2,3-(Cp*Ru)2B4H8, 6, with a BH-capped square pyramidal structure. Finally, 6 reacts with Fe2(CO)9 to yield pileo-6-Fe(CO)3-2,3-(Cp*Ru)2(μ3-CO)B4H4, 7, with a BH-capped octahedral cluster structure. The overall isolated yield of 7, formed in four steps from [Cp*RuCl2]2, is ≈50% and evidences good control of reactivity.

Chemistry of Dimetallaboranes Derived from the Reaction of [CpMCl₂]₂with Monoboranes (M = Ru, Rh; Cp = η5-C₅Me₅)

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