MICROWAVE SPECTRUM OF GERMACYCLOPENTANE

The microwave spectrum of four Ge isotopic species of the five-membered heterocycle germacyclopentane (C4H10Ge) has been investigated in the region 8-22 GHz. Rotational constants for the ground state of the 74Ge species are: A =5323.7, B = 2842.20, C = 2041.52 MHz. From excited states assigned to the lowest ring-deformation mode, a lower limit of about 500 cm-1 has been estimated for the barrier to pseudorotation. The molecule is found to be permanently twisted into a C 2 conformation with a twist angle of 18°, ∠ CGeC = 98°, ∠ GeCC = 106°, and ∠ CCC = 115°. Stark-effect measurements give a dipole moment of 0.665±0.007 D. For the 73Ge species, the nuclear quadrupole coupling constants are found to be xaa = 15.89 MHz, xbb = -10.29 MHz, xcc= -5.60 MHz.