Plasticity of the five-membered chelate ring in [PdCl2(1,2-(PR2)2-1,2-C2B10H10)] complexes (R = 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)].