The Syntheses and Vibrational Spectra of 16O- and 18O-Enriched cis-MO2 (M=Mo, W) Complexes

Abstract

In this contribution, we report convenient synthetic approaches for obtaining 16O/18O‐enriched dioxidometalVI complexes, MO2(L) (W, Mo), with a linear, tetradentate amine phenolate ligand N,N′‐dimethyl‐N,N′‐bis(2‐hydroxy‐3,5‐dimethylbenzyl)ethylenediamine (H2L) and describe their characterization by IR and Raman spectroscopy complemented by DFT computational analysis. The isotopologues of WO2(L) were made of tungstenVI trisglycolate W(eg)3 (eg=1,2‐ethanediolate dianion) and ligand H2L in the presence of either H2[16O] or H2[18O], whereas Mo16O2(L) was made using Na2MoO4⋅2H2O which was converted to Mo18O2(L) by oxido substitution using H2[18O]. The complementary IR and Raman analyses show the ν(MO2)s and ν(MO2)a at 934 and 899 cm–1 for W16O2(L) and at 914 and 898 cm–1 for Mo16O2(L), respectively. In the vibrational spectra of the 18O substituted derivatives, the ν(MO2)s were shifted to lower energy by 43 cm–1 for W18O2(L) and by 41 cm–1 for Mo18O2(L) whereas asymmetric MO2 stretches in the IR were partially overlapped by an organic ligand related stretch. However, Raman spectroscopy, accompanied by DFT calculations, allowed the deciphering the ν(MO2)a shifts of 47 cm–1 for W18O2(L) and 31 cm–1 for Mo18O2(L).