METHYLPHOSPHINIDENE (CH3P) AND ITS REARRANGEMENT TO PHOSPHAETHYLENE (CH2PH) - TOWARD THE OBSERVATION OF GROUND-STATE TRIPLET CH3P

The CH3P radical, which may be produced in the pyrolysis of (CH3)3P, has not been observed experimentally. Starting from the potential energy surfaces for the CH3P --> CH2PH rearrangement, we examine the properties of the lowest singlet (1A') and triplet (3A2) States of CH3P. The geometry optimizations are performed at the CISD level of theory with the TZ2P+f basis set. For the closed-shell singlet state of CH2=PH, the highest level and basis set is the CCSD level with the TZ2P basis. The lowest singlet state of CH3P is described starting from the two-configuration (TC) SCF method. As expected, the lowest excited singlet and triplet states of CH3P are subject to Jahn-Teller distortion and thus exhibit C(s) symmetry. The singlet-triplet energy separations for CH3P and CH2PH are predicted to be -22.6 and 41.7 kcal/mol, respectively. The triplet-triplet excitation energy for CH3P is also predicted and compared with the experimental value for the parent molecule, PH. The theoretical geometry for the ground state (1A') of CH2PH agrees well with the experimental structure.