The synthesis and characterisation of homo- and heterobimetallic 1,14,2,9- and 1,14,2,10-M2C2B10 14-vertex metallacarboranes.

A high-yielding synthesis of the 13-vertex cobaltacarborane 4-Cp-4,1,12-closo-CoC(2)B(10)H(12) is described and this compound used to prepare the known 14-vertex species 1,14-Cp(2)-1,14,2,10-closo-Co(2)C(2)B(10)H(12) (II) and 1-(p-cymene)-14-Cp-1,14,2,10-closo-RuCoC(2)B(10)H(12) (IV), the latter by a new route. The related species 1,14-Cp(2)-2,10-Me(2)-1,14,2,10-closo-Co(2)C(2)B(10)H(10) (1) and 1,14-(η-C(9)H(7))(2)-1,14,2,10-closo-Co(2)C(2)B(10)H(12) (2) are also reported. Polyhedral expansion of 4,1,8-CoC(2)B(10) compounds affords a different isomer of the 14-vertex bimetallacarboranes, 1,14,2,9-Co(2)C(2)B(10), and three examples, 1,14-Cp(2)-1,14,2,9-closo-Co(2)C(2)B(10)H(12) (3), 1,14-Cp(2)-2,9-Me(2)-1,14,2,9-closo-Co(2)C(2)B(10)H(10) (4) and 1,14-(η-C(9)H(7))(2)-1,14,2,9-closo-Co(2)C(2)B(10)H(12) (5), are prepared and characterised. Patterns in (11)B NMR chemical shifts and in <δ(11)B>, the weighted average (11)B chemical shift, within and between related isomers of the 14-vertex compounds II and 1-5 are discussed. Compounds II, IV, 2, 4 and 5 were studied crystallographically, with cage C atom positions in these and related bicapped hexagonal antiprismatic 1,14,2,x-M(2)C(2)B(10) species analysed by the Vertex-to-Centroid Distance method.