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).

Bioinspired Mo, W and V complexes bearing a highly hydroxyl-functionalized Schiff base ligand

“…[29] Specifically, the characteristic symmetric and asymmetric ν(MO2) (M = Mo, W ) stretches are found at 930 and 889 cm -1 for 1, and at 946 and 893 cm -1 for 2, respectively. [47] These are in line with what has been reported for similar dioxidomolybdenum complexes. [60] For 3, featuring only a single oxido ligand, a characteristic ν(V=O) stretching vibration is found at 952 cm -1 , which is consistent with experimental values obtained for other oxidovanadium(V) complexes bearing similar ligands.…”

“…IR/cm -1 ATR mode: ν 3500-3000vb (ROH, R(CH2OH)2), 2958-2850s (C-H, t-Bu), 1621s (RCH=N), 1566-1362m (arom. C=C), 1300m (C-O, ArOH), 1048vs (C-O, R(CH2OH)2 and R(CH2O -)), 893vs νs(WO2) [45][46][47][48] 860vs νas(WO2) [45][46][47][48], 764m, 561s ν(W-N) [49] 2 could be also synthesized using equimolar amounts of H4L Saltris and [W(eg)3]. The isolated yield of a 1 mmol scale synthesis was very low, only 40 mg (9 %).…”

Catalytic epoxidation using dioxidomolybdenum(VI) complexes with tridentate aminoalcohol phenol ligands

“…The IR spectra for the mononuclear MoO2(VI) complexes (1, 3 and 5) exhibit two strong νMo=O bands around 901-920 and 929-953 cm -1 corresponding to the antisymmetric and symmetric stretching modes, respectively, for the cis-[MoO2] 2+ moiety [26][27][28]. Broad bands at ~ 3087-3395 cm -1 are characteristic for coordinated or hydrogen bonded methanol molecules.…”

Biomimetic Oxidative Bromination by cis‐Dioxidotungsten(VI) Complexes of Salan Type N,N’‐Capped Linear Tetradentate Amino Bisphenol

“…After the first report on dioxidotungsten(VI) complexes of hydrogenated analogue of H 2 salen [N,N’‐ethylenebis(salicylideneimine)] (i.e. H 2 salan) and related ligands, [13a] groups of Lehtonen and Mösch‐Zanetti have reported dioxidotungsten(VI) complexes of N‐methyl derivatives of H 2 salan type ligands [9,13b,c] …”