Potential energy surfaces for all-trans P5H6(+) and P5Me6(+) may be less complicated than anticipated.
Burford and co-workers recently (2007) investigated the synthesis, structure, and pseudorotation of a family of cyclotetraphosphinophosphonium ions comprehensively. We now report theoretical computations through the CCSD(T) level to study the conformations of the parent model rings, P5H6(+) and P5Me6(+). The all-trans conformations on the full pseudorotational cycle for the cyclotetraphosphinophosphonium cation (P5H6(+)) and for its methyl-substituted derivative (P5Me6(+)) were located systematically on their potential energy surfaces. The potential energy for the pseudorotational circuit of P5H6(+) is smooth and monotonic with only one minimum ((3)T4) and one maximum ((4)T3), but the analogous P5Me6(+) circuit has two minima. The P5H6(+) and P5Me6(+) potential surfaces appear to be qualitatively very different from that for the well investigated tetrahydrofuran. Since the (3)T4 form of P5H6(+)avoids unfavorable eclipsing PH-PH and lone pair-lone pair interactions, it is the global minimum among all possible P5H6(+) configurations and conformations.
Li
Qian-Shu
QS
School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081, China. qsli@scnu.edu.cn
Pu
Zhifeng
Z
Xie
Yaoming
Y
Schleyer
Paul von Rague
Pv
Schaefer
Henry F
HF