Rational, Facile Synthesis and Characterization of the Neutral Mixed‐Metal Organometallic Oxides Cp*₂Mo_xW_6–xO₁₇ (Cp* = C₅Me₅, x = 0, 2, 4, 6)

Abstract

The reaction of the bis(pentamethylcyclopentadienyl)pentaoxidodimetal complexes Cp*2M2O5 with four equivalents of Na2M′O4 (M, M′ = Mo, W) in acidic aqueous medium constitutes a soft and selective entry into neutral Lindqvist‐type organometallic mixed‐metal oxides Cp*2MoxW6–xO17 [x = 6 (1), 4 (2), 2 (3), 0 (4)]. The identity of the complexes is demonstrated by elemental analyses, thermogravimetric analyses and infrared spectroscopy. Thermal degradation of 1–4 up to above 500 °C leads to Mox/6W1–x/6O3. The molecular identity and geometry of compound 2 is further confirmed by a fit of the powder X‐ray diffraction pattern with a model obtained from previously reported single‐crystal X‐ray structures of 1 and 4, with which 2 is isomorphous. DFT calculations on models obtained by replacing Cp* with Cp (I–IV) validate the structural assignments and assist in the assignment of the M,M′–O vibrations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Oxo-bridged bis oxo-vanadium(V) complexes with tridentate Schiff base ligands (VOL)2O (L=SAE, SAMP, SAP): Synthesis, structure and epoxidation catalysis under solvent-free conditions

“…Greater shifts are noted for the vibrations of doubly bonded moieties, whereas a closer agreement is found for the V-O-V vibration. The same trend has been observed for higher nuclearity tungsten and molybdenum polyoxometalates [30]. This phenomenon is probably related to the greater discrepancy between calculated and observed bond distances for the bonds of higher multiplicity.…”

Rational Synthesis and Characterization of the Mixed-Metal Organometallic Polyoxometalates [Cp*MoxW6–xO18]− (x = 0, 1, 5, 6)

“…This trend has also been noted for the isoelectronic Cp*2MoxW6-xO17 series. 45 analysis clearly shows that there is a driving force for the POM structure to distort away from maximum symmetry, not solely related to crystal packing. However, the crystal packing (nature of the cation) has the effect of driving this distortion in different directions.…”

“…Compound 1a has already been previously reported and characterized, including by a single crystal X-ray diffraction study, but was synthesized by a different method in a lower yield (see Introduction). 50 The selectivity of the synthetic strategy is worthy of note: the reaction could have resulted, for instance, in a mixture of the previously The success of this synthesis, as well as that of the related neutral Cp*2MoxW6-xO17 compounds, 45 relies on the high stability of Cp*M bond in Cp*2M2O5 toward protonolysis at any pH. 43 Thus, it is possible to use the "Cp*M" moieties as an elementary building block, especially at low pH, due to the ionic splitting of Cp*2M2O5 into Cp*MO2(H2O) + and Cp*MO2 + .…”

“…By analogy with the previously reported mixed-metal neutral compounds, 45 DFT geometry optimizations were carried out on the isoelectronic anionic [Cp*MM'5O18]complexes in order to interpret the IR absorption spectrum in the M=O stretching region and to understand the effect on them of the metal nature. To save computational time, simplified models were used where the Cp* ligands were replaced by Cp rings.…”

“…31,35 POMs grafted with organometallic fragment have attracted interest [36][37][38][39][40][41][42] 42 Recently, we have reported the use of Cp*2M2O5 (M = Mo, W), compounds that are stable in air and in aqueous solution in the entire pH range, 43 in combination with the inorganic salts Na2M'O4 (M' = Mo, W) in a 1:4 ratio, as precursors of the hexanuclear organometallic polyoxometallic complexes Cp*2MoxW6-xO17 (x = 0, 2, 4, 6) in a selective, high-yielding, room temperature aqueous reaction. 44,45 The formula of these compounds may also be written as [ [46][47][48] two adjacent metallic atoms bear a Cp* ligand in place of a terminal oxido ligand, leading to a neutral compound.…”