Synthesis and/or molecular structures of some simple 2,1,7- and 2,1,12-ruthena- and cobaltacarboranes

Abstract

The ruthenacarboranes 2-(p-cymene)-2,1,7-closo-RuC2B9H11 (2) (p-cymene = 1-methyl-4-isopropylbenzene) and 2-(p-cymene)-2,1,12-closo-RuC2B9H11 (3) have been synthesised by simple metallation of [7,9-nido-C2B9H11]2– and [2,9-nido-C2B9H11]2–, respectively. In preparing the known cobaltacarborane 2-(η-C5H5)-2,1,12-closo-CoC2B9H11 (6), the new bis(dicarbollide) [2,2′-Co(1,12-closo-C2B9H11)2]– (as its [(η-C5H5)2Co]+ salt; 7) was also formed. Molecular structures of 2, 3, 6 and 7 and that of the known compound 2-(η-C5H5)-2,1,7-closo-CoC2B9H11 (5) have been determined. Patterns in 〈δ(11B)〉, the weighted average 11B NMR chemical shift, of these metallacarboranes, together with those in 3-(p-cymene)-3,1,2-closo-RuC2B9H11 (1) and 3-(η-C5H5)-3,1,2-closo-CoC2B9H11 (4) are discussed in relation to 〈δ(11B)〉 in the parent carboranes 1,2-closo-C2B10H12, 1,7-closo-C2B10H12 and 1,12-closo-C2B10H12. The similarity between the 1H and 11B spectra of 6 and 7 confirm the isolobality of the [C5H5]– and [C2B9H11]2– ligands. An electrochemical study of 7 confirms that trends in the potential of the CoIII/CoII couple for the series of isomers of (η-C5H5)CoC2B9H11 are reproduced for the bis(dicarbollides) [Co(C2B9H11)2]–. The molecular structures of compounds 1–3 as a family and 4–6 as a family provide a unique opportunity to consider structural patterns in simple isomeric metallacarboranes.