Facile Formation of Molybdenum(VI) Monooxo Aryloxides MoO(OAr)4-nCln from Molybdenum Dioxo Dichloride

N-Heterocyclic Carbene-Supported Aryl- and Alk- oxides of Beryllium and Magnesium

Recently, we have witnessed significant progress with regard to the synthesis of molecular alkaline earth metal reagents and catalysts. To provide new precursors for light alkaline earth metal chemistry, molecular aryloxide and alkoxide complexes of beryllium and magnesium are reported. The reaction of beryllium chloride dietherate with two equivalents of 1,3-diisopropyl-4,5-dimethylimidizol-2-ylidine (sIPr) results in the formation of a bis(N-heterocyclic carbene) (NHC) beryllium dichloride complex, (sIPr)2BeCl2 (1). Compound 1 reacts with lithium diisopropylphenoxide (LiODipp) or sodium ethoxide (NaOEt) to form the terminal aryloxide (sIPr)Be(ODipp)2 (2) and alkoxide dimer [(sIPr)Be(OEt)Cl]2 (3), respectively. Compounds 2 and 3 represent the first beryllium alkoxide and aryloxide species supported by NHCs. Structurally related dimers of magnesium, [(sIPr)Mg(OEt)Brl]2 (4) and [(sIPr)Mg(OEt)Me]2 (5), were also prepared. Compounds 1-5 were characterized by single crystal X-ray diffraction studies, 1H, 13C, and 9Be NMR spectroscopy where applicable.

Mono-oxo molybdenum(vi) and tungsten(vi) complexes bearing chelating aryloxides: synthesis, structure and ring opening polymerization of cyclic esters

Mono-oxo Mo and W complexes bearing di- or tetra-phenolates were active for the ROP of small cyclic esters, albeit with poor control. Related metallocalix[4]arenes were less active.

A novel dinuclear MoVI complex with tris(3,5-dimethyl-1H-pyrazol-1-yl)methane

Recrystallization of [MoO(2)Cl{HC(3,5-Me(2)pz)(3)}]Cl [where HC(3,5-Me(2)pz)(3) is tris(3,5-dimethyl-1H-pyrazol-1-yl)methane] led to the isolation of large quantities of the dinuclear complex dichlorido-2κ(2)Cl-μ-oxido-κ(2)O:O-tetraoxido-1κ(2)O,2κ(2)O-[tris(3,5-dimethyl-1H-pyrazol-1-yl-1κN(2))methane]dimolybdenum(IV) acetonitrile monosolvate, [Mo(2)Cl(2)O(4)(C(16)H(22)N(6))]·CH(3)CN or [{MoO(2)Cl(2)}(μ(2)-O){MoO(2)[HC(3,5-Me(2)pz)(3)]}]·CH(3)CN. At 150 K, this complex cocrystallizes in the orthorhombic space group Pbcm with an acetonitrile molecule. The complex has mirror symmetry: only half of the complex constitutes the asymmetric unit and all the heavy elements (namely Mo and Cl) are located on the mirror plane. The acetonitrile molecule also lies on a mirror plane. The two crystallographically independent Mo(6+) centres have drastically different coordination environments: while one Mo atom is hexacoordinated and chelated to HC(3,5-Me(2)pz)(3) (which occupies one face of the octahedron), the other Mo atom is instead pentacoordinated, having two chloride anions in the apical positions of the distorted trigonal bipyramid. This latter coordination mode of Mo(VI) was found to be unprecedented. Individual complexes and solvent molecules are close-packed in the solid state, mediated by various supramolecular contacts.