1,1′-Bis(ortho-carborane) as a κ² co-ligand

The compounds (dmpe)Ni{κ²-2,2′-[1-(1′-1′,2′-closo-C₂B₁₀H₁₀)-1,2-closo-C₂B₁₀H₁₀]} (1) and (dppe)Ni{κ²-2,2′-[1-(1′-1′,2′-closo-C₂B₁₀H₁₀)-1,2-closo-C₂B₁₀H₁₀]} (2) have been synthesised and fully characterised, including crystallographic studies. In all three structures studied (1, 2 and 2·2THF) the metal atom is slightly distorted from square-planar towards tetrahedral (τ₄ values [Houser et al., 2007] of 0.30, 0.33 and 0.11, respectively). Consideration of these molecular structures together with those of related species in the literature allows us to tentatively conclude that, in square-planar Ni^IIcompounds, the structural trans effect (trans influence) of σ-bonded carborane is greater than that of Cl and sp² N but less than that of sp² C and sp³ C.