Vapour density and vibrational spectra of MoOF4 and WOF4. The structure of crystalline WOF4

Abstract

Vapour density measurements on MoOF₄ show this compound to be monomeric in the gas phase. Similar measurements on WOF₄ show it to be essentially monomeric as a gas, although some association may occur at lower temperatures and higher pressures. Gas-phase Raman spectra of WOF₄ are invariant in the range 200–600° and closely similar to those of the melt and solid. The results demonstrate that solid WOF₄ is not principally an oxygen-bridged polymer. The spectra of MoOF₄ are closely similar to those of WOF₄ in all phases. Detailed studies of the gas-phase and matrix-isolated vibrational spectra of WOF₄, including structure of gas phase i.r. bands and Raman depolarization data, strongly suggest that the molecule is a square pyramid with an apical oxygen.