Twisted [(R3P)PdX] groups above dicarbaborane ligands: 4-dimethylsulfido-3-iodo-3-triphenylphosphine-closo-3-pallada-1,2-dicarbadodecaborane and 3-dimethylphenylphosphine-3-chloro-4-dimethylsulfido-closo-3-pallada-1,2-dicarbadodecaborane

The structural analyses of [3-(PPh3)-3-I-4-(SMe2)-closo-3,1,2-PdC2B9H10] or [Pd(C4H16B9S)I(C18H15P)], (I), and [3-(PPhMe2)-3-Cl-4-(SMe2)-closo-3,1,2-PdC2B9H10] or [Pd(C4H16B9S) Cl(C8H11P)], (II), show that in comparison with [3(PR3)(2)-closo-3,1,2-PdC2B9H11] the presence of the 4-SMe2 group causes the [PdX(PR3)] unit (X=halogen) to twist about an axis passing through the Pd atom and the directly opposite B atom of the carbaborane ligand. The halogen atoms are located almost directly above a C atom in the C2B3 face, and the conformations of the [PdX(PR3)] units above the C2B3 faces are not those predicted from molecular orbital calculations of the closo-3,1,2-PdC2B9 system. The fact that the variation from the predicted conformation is greater in the case of (I) than in (II) may be ascribed to the greater steric interactions induced by the I atom in (I) compared with the Cl atom in (II).