Synthesis, Microwave Spectrum, Quantum Chemical Calculations, and Conformational Composition of the Novel Compound Cyclopropylethylidynephosphine (C₃H₅CH₂C≡P)

Abstract

The synthesis of the novel compound cyclopropylethylidynephosphine (C3H5CH2C≡P) and its microwave spectrum are reported together with quantum chemical calculations. The spectrum, which reveals the existence of two conformers, has been recorded in the 38-109 GHz spectral range at room temperature. The H-C-CH2-C chain of atoms is synclinal in one rotamer denoted sc, and antiperiplanar in the second conformer called ap. The spectra of the ground vibrational state and two vibrationally excited states were assigned for each rotamer. The vibrational frequencies of these excited states were determined by relative intensity measurements. Relative intensity measurements were also conducted to determine the energy difference between ap and sc. The latter conformer was found to be the lower-energy form and E(ap) - E(sc) was determined to be 0.9(4) kJ/mol. The microwave study has been augmented by quantum chemical calculations at the CCSD/cc-pVQZ and MP2/cc-pVTZ levels of theory. The CCSD predictions were generally in good agreement with experiment, while somewhat mixed results were obtained in the MP2 calculations.

On the Spectroscopy of Phosphaalkynes: Millimeter- and Submillimeter-Wave Study of C2H5CP

“…For detailed accounts on the available laboratory spectroscopic data of individual species, the interested reader may consult the reports on phosphaethyne, HCP, 9,10 HC 3 P, 9,11 HC 5 P, 12,13 NCCP, 9 NC 4 P, 14,15 C 2 H 3 CP, 16 CH 3 CP, 17,18 PhCP, 19 and C 3 H 5 CH 2 CP. 20 It should be noted that while to this day, spectroscopic signatures of only two phosphaalkynes, HCP and NCCP, have been found in space, 21,22 not all of the above species have yet been characterized in the laboratory at a level meeting the needs of radio astronomy. In addition, other potentially astronomically relevant phosphaalkynes still await laboratory (high-resolution) spectroscopic characterization.…”

“…Since the first microwave spectroscopic studies of prototypical phosphaethyne (HCP), and a handful of other selected species studied by Kroto and collaborators (HC 3 P, CH 3 CP, NCCP, C 2 H 3 CP, PhCP; see Burckett-St. Laurent et al and references therein), only a small number of additional phosphaalkynes have been characterized employing high-resolution (rotational) spectroscopy. For detailed accounts on the available laboratory spectroscopic data of individual species, the interested reader may consult the reports on phosphaethyne, HCP, , HC 3 P, , HC 5 P, , NCCP, NC 4 P, , C 2 H 3 CP, CH 3 CP, , PhCP, and C 3 H 5 CH 2 CP …”

What Types of Noncovalent Bonds Stabilize Dimers (XCP)2, for X = CN, Cl, F, and H?

“…The structure of the protonated parent molecule, H 2 CP + , has been explored with a variety of computational methods . Other members of this family of monomers including those with X = F, Cl, CN, and alkyl groups , have been characterized experimentally . It is noteworthy that the HCP molecule was the first isolated system with a carbon to phosphorus triple bond.…”