Twisted [( R 3 P)Pd X ] 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‐(PPh 3 )‐3‐I‐4‐(SMe 2 )‐ closo ‐3,1,2‐PdC 2 B 9 H 10 ] or [Pd(C 4 H 16 B 9 S)I(C 18 H 15 P)], (I), and [3‐(PPhMe 2 )‐3‐Cl‐4‐(SMe 2 )‐ closo ‐3,1,2‐PdC 2 B 9 H 10 ] or [Pd(C 4 H 16 B 9 S)Cl(C 8 H 11 P)], (II), show that in comparison with [3‐(P R 3 ) 2 ‐ closo ‐3,1,2‐PdC 2 B 9 H 11 ] the presence of the 4‐SMe 2 group causes the [Pd X (P R 3 )] 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 C 2 B 3 face, and the conformations of the [Pd X (P R 3 )] units above the C 2 B 3 faces are not those predicted from molecular orbital calculations of the closo ‐3,1,2‐PdC 2 B 9 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).