Structure, ab initio harmonic force field and infrared spectrum of CH3CAs

The experimental r(z) and r(e) structures of ethylidynearsine, CH3C=As, were calculated using the experimental ground state rotational constants of eight isotopic species and an ab initio harmonic force field calculated at the B3LYP/6-311++G(3df,2pd) level and scaled using the experimental centrifugal distortion constants. For comparison the structure was calculated ab initio at the MP2 level. The average geometry is: r(z)(C-H) = 1.097 (2) Angstrom, r(z)(C-C) = 1.467 (2) Angstrom, r(z)(C=As) = 1.659 (2) Angstrom, angle(z)(HCC) = 110.6 (2)degrees and the equilibrium one: r(e)(C-H) = 1.091 (3) Angstrom, r(e)(C-C) = 1.465 (2) Angstrom, r(e)(C=As) = 1.658 (2) Angstrom, angle(e)(HCC) = 110.6 (2)degrees. The infrared spectrum was studied at low resolution and the analysis of the nu(4) band investigated by high resolution Fourier transform spectroscopy is presented. The center of the band was found at 627.913 289 (44) cm(-1). (C) 1999 Elsevier Science B.V. All rights reserved.