MICROWAVE INVERSION ROTATION SPECTRUM AND RING-PUCKERING VIBRATION OF 1,3-DISILACYCLOBUTANE-1,1,3,3-D4
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1,3-Disilacyclobutane-1,1,3,3-d4 was studied by microwave spectroscopy in the frequency region from 20 to 75 GHz. More than 300 absorption lines were assigned to inversion-rotation transitions between the lowest inversion doublet of the ring-puckering vibration with a separation of about 1.4 cm-1. A least-squares analysis yielded the rotational constants and quartic centrifugal distortion constants for the upper and lower states of the doublet as well as the energy separation between them. The centrifugal distortion constants differ considerably between the upper and lower states of the doublet, which may be reasonably accounted for by a perturbation treatment based on the one-mode approximation. The molecular geometry inferred from the rotational constants suggests that the CSiC angle is larger (less deviating from the tetrahedral angle) than SiCSi, which is discussed in connection with the concept of the bent bond. The rotational constants also allow us to infer the change of the molecular geometry during the ring-puckering motion. The dipole moment for the inversion transition was determined from the Stark effect measurement. 1988.
