Plasticity of the five-membered chelate ring in [PdCl2(1,2-(PR2)2-1,2-C2B10H10)] complexes (RÂ =Â H or iPr)

Gradient-corrected density functional theory applied to 1,2-diphosphino-1,2-dicarba-closo-dodecaborane, 1,2-(PH2)2-1,2-C2B10H10, and its respective PdCl2 complex presents a clear picture of the effect of complexation on the P-Cc-Cc-P fragments (Cc = cage carbon C1 or C2) in the structures. The complexation results in clear closing in the P-Cc-Cc angles and shortening of Cc-Cc bond, but only minor changes take place in the P-Cc-Cc-P torsion angle. Furthermore, complexation brings along shortening of the P-Cc bonds with concomitant increase of covalency, as revealed by atoms-in-molecules calculations. Although there is also change in the Cc-Cc distance in the cage, no significant change is involved in the bonding. These findings are compared with the results obtained by single-crystal X-ray study for [PdCl2(1,2-(PiPr2)2-1,2-C2B10H10)] and additional calculations carried out for [PdCl2(1,2-(PH2)2-C2H4)].