THE PREPARATION AND CRYSTAL STRUCTURE OF DIMOLYBDENUM TETRAFORMATE; PHOTOELECTRON SPECTRA OF THIS AND SEVERAL OTHER DIMOLYBDENUM TETRACARBOXYLATES

Abstract

The compound Mo₂ (O₂CH)₄ is described in detail for the first time and its crystal structure is reported. Crystallographic parameters are: Space group: P2₁ 2₁ 2₁; a = 12.288(4)Å; b = 12.930(5)Å; c = 5.500(1)Å, and Z = 4. Using 952 reflections for which I < 3 [sgrave](I) the structure has been solved and refined to R ₁ = 0.063 and R ₂ = 0.071. The molecule has virtual symmetry D₄ h and all comparable dimensions are virtually identical to those of Mo₂ (O₂ CCH₃)₄; for example, the Mo—Mo distance is 2.091(2)Å. The Raman spectrum has a band at 403 cm⁻¹ due mainly to Mo—Mo stretching. The photoelectron spectra of the Mo₂ (O₂CR)₄ compounds with R = H, CH₃ and CF₃ are reported. The spectra are qualitatively similar and exhibit trends in accord with the relative electronegativities of the R groups, in harmony with the results of an earlier study which also included the formate and acetate.