One pot-synthesis of the fourth category of dinuclear molybdenum(VI) oxalate series: Structure and study of thermal and redox properties

Abstract

Three new dinuclear molybdenum(VI) oxalate (Pr 2 NH 2) 4 •[M�0 6 (¼0 4 hl (1), (�r 2 NH;J 4 •[M�0 6 (¼0 4 h] (2) and (HDabco) 4 [Mo 2 0 6 (C 2 0 4 hJ-2H 2 0 (3) compounds, have been prepared by one pot-synthesis at room temperature and characterized by single crystal X-ray diffraction and vibrational spectroscopies. F.ach compound contains the binuclear [Mo 2 0 6 (¼0 4 h] 4-anion where each molybdenum is in an octahedral Mo0 6 environment. ln compound (3), the interconnection between [M0206(C204)2J 4-anions, [HDabco] + cations and water molecules (H20) leads to an infinite inorganic-organic chain structure. Similarly, in compounds (1) and (2) the interactions between [Mo206(C2Ü 4hJ4-anions and respectively [Pr 2NH2l + and [ i Pr�2l + cations leads to an infinite inorganic-organic chain structure. A remarkable difference between the compounds is that in compounds (1) and (2) interactions between the chains involve only Van der Waals forces giving rise to layer-like structures, which also interact between them only by Van der Waals forces, whereas in compound (3) the chains interact also through hydrogen bonds giving a 30 supramolecular structure. The thermal properties of the compounds were investigated through thermogravimetric and differential thermal analyzes. The differences in the thermal decomposition of the compounds in the solid state are discussed in relation with their crystal structure. Cyclic voltammetry shows that the [Mo 2 0 6 (¼0 4 h] 4-anion can be reduced in both aprotic solvent and water.

Electrochemical and X-ray structural evidence of multiple molybdenum precursor candidates from a reported non-aqueous electrodeposition of molybdenum disulfide

“…One similar non-anionic dimer features a structurally similar bidentate mono-deprotonated tetramethyl ethylene glycol and two bridging methoxide ligands; however, this dimer is a cis -dioxo rather than mono-oxo molybdenum compound like compounds 2 and 3 , which is also unique in having an additional bridging THF ligand. 47 Other similar dimeric examples often contain ammonium, 48 phosphonium, 49 alkali, 49 or alkaline earth 50,51 cations, co-crystallized solvents like water, 51,52 ethanol, 53 methanol, 54 toluene 55 or benzene. 56 Coordinating solvents like water, 51 ethanol, 53 or pyridine 48 along with bridging oxo, 48 alkoxide, 54,56 phosphate, 57 hydroxide, 58 oxalato, 48 citrato, 59 or dioxomolybdenum 60 groups either between the Mo dimer atoms or bridging pairs of dimers has also observed.…”

“…The second reaction again resulted in a golden viscous liquid upon concentration in vacuo of the crude reaction mixture, though extraction with dichloromethane, drying in vacuo again crystalline molybdenum dimers with each molybdenum bound to a single oxo group (2−), an ethylene glycoxide ligand (2−), and a bridging ethylene hydroxy glycoxide (1−), although similar dimers with different ligands exist with similar bridging of the two Mo atoms by oxygen-based ligands. [47][48][49][50][51][52][53][54][55][56][57][58][59][60] Related molybdenum dimers have had their structure reported in the CSD, specically with each Mo atom in the dimer containing a non-bridging single oxo ligand and a bidentate O-C-C-O structured ligand. One similar non-anionic dimer features a structurally similar bidentate mono-deprotonated tetramethyl ethylene glycol and two bridging methoxide ligands; however, this dimer is a cis-dioxo rather than mono-oxo molybdenum compound like compounds 2 and 3, which is also unique in having an additional bridging THF ligand.…”