Cyclopentadienylmolybdenum(VI) and Molybdenum(V) Oxo Chemistry: New Synthetic and Structural Features

Abstract

Convenient syntheses for Cp, Cp*, and related cyclopentadienyl derivatives ( 4 Cp = C 5 HiPr 4 ; CpЈЈЈ = C 5 H 2 tBu 3 -1,2,4) of formula [(Ring) 2 Mo 2 O 5 ] are described. Compound [Cp 2 Mo 2 O 5 ] was produced in good yields by the rapid oxidation of red [CpMoO 2 ] 4 with PhIO in CH 2 Cl 2 . [Cp* 2 Mo 2 O 5 ] was obtained by CH 3 COOH acidification of aqueous solutions of [Cp*MoO 3 ] − Na + , the latter being generated in a single step from [Cp*MoCl 4 ] and more than 5 equiv. of aqueous NaOH in air. Minor quantities of [Cp*MoO 2 ] 2 were also isolated from this reaction, although the formation of this by-

Molybdenum Oxo and Imido Complexes of β-Diketiminate Ligands: Synthesis and Structural Aspects

“…A vaguely related compound represents the octamolybdenum oxo-pyrazolate cluster containing [Mo 2 O 2 ] 2+ cores bridged by anionic pyrazolates . The IR spectrum of 1 revealed a vibration typical for terminal MoO groups at 959 cm -1 and one due to the Mo−O−Mo stretching vibration at 762 cm -1 , which is in a good agreement with literature compounds. , …”

Molybdenum Oxo and Imido Complexes of β-Diketiminate Ligands: Synthesis and Structural Aspects

“…A vaguely related compound represents the octamolybdenum oxo-pyrazolate cluster containing [Mo 2 O 2 ] 2+ cores bridged by anionic pyrazolates . The IR spectrum of 1 revealed a vibration typical for terminal MoO groups at 959 cm -1 and one due to the Mo−O−Mo stretching vibration at 762 cm -1 , which is in a good agreement with literature compounds. , …”

Mononuclear and Binuclear Cyclopentadienyl Oxo Molybdenum and Tungsten Complexes: Syntheses and Applications in Olefin Epoxidation Catalysis

“…Treatment of 1 with 2 equiv of AllylMgBr led to a diamagnetic microcrystalline yellow solid. 1 H and 13 C NMR spectra of this complex show one set of CpBz resonances, and elemental analysis is consistent with the formulation [Mo-(CpBz)Cl 2 ] 2 (6). The formation of 6 excludes the occurrence of chloride metathesis and suggests that the attack of the Grignard reagent takes place through electrophilic abstraction of the oxo ligand by magnesium, resulting in metal reduction.…”

A Simple Entry to (η5-C5R5)chlorodioxomolybdenum(VI) Complexes (R = H, CH3, CH2Ph) and Their Use as Olefin Epoxidation Catalysts

“…A comparable increase in stability in comparison to compound 5 has also been stated for [Mo(η 5 -C 5 Ph 4 (2,5-dimethoxyphenyl))O 2 Br] 6f and was ascribed to the steric bulk of the ligand. 6f, For prolonged storage complexes 4 and 5 should be kept below room temperature (refrigerator); otherwise they decompose under formation of intractable blue solids 6e. The decomposition of compounds 4 and 5 has been already described in the literature, and it has been stated that light accelerates its decomposition 6e. In this respect it is worth noting that the stability of these complexes increases upon dilution in water-free solvents, a fact that has already been noted for most of the RReO 3 complexes although never properly understood .…”

Molybdenum Oxo and Imido Complexes of β-Diketiminate Ligands: Synthesis and Structural Aspects

“…A vaguely related compound represents the octamolybdenum oxo-pyrazolate cluster containing [Mo 2 O 2 ] 2+ cores bridged by anionic pyrazolates . The IR spectrum of 1 revealed a vibration typical for terminal MoO groups at 959 cm -1 and one due to the Mo−O−Mo stretching vibration at 762 cm -1 , which is in a good agreement with literature compounds. , …”

Mononuclear and Binuclear Cyclopentadienyl Oxo Molybdenum and Tungsten Complexes: Syntheses and Applications in Olefin Epoxidation Catalysis

“…Treatment of 1 with 2 equiv of AllylMgBr led to a diamagnetic microcrystalline yellow solid. 1 H and 13 C NMR spectra of this complex show one set of CpBz resonances, and elemental analysis is consistent with the formulation [Mo-(CpBz)Cl 2 ] 2 (6). The formation of 6 excludes the occurrence of chloride metathesis and suggests that the attack of the Grignard reagent takes place through electrophilic abstraction of the oxo ligand by magnesium, resulting in metal reduction.…”

A Simple Entry to (η5-C5R5)chlorodioxomolybdenum(VI) Complexes (R = H, CH3, CH2Ph) and Their Use as Olefin Epoxidation Catalysts

“…A comparable increase in stability in comparison to compound 5 has also been stated for [Mo(η 5 -C 5 Ph 4 (2,5-dimethoxyphenyl))O 2 Br] 6f and was ascribed to the steric bulk of the ligand. 6f, For prolonged storage complexes 4 and 5 should be kept below room temperature (refrigerator); otherwise they decompose under formation of intractable blue solids 6e. The decomposition of compounds 4 and 5 has been already described in the literature, and it has been stated that light accelerates its decomposition 6e. In this respect it is worth noting that the stability of these complexes increases upon dilution in water-free solvents, a fact that has already been noted for most of the RReO 3 complexes although never properly understood .…”

Molybdenum Oxo and Imido Complexes of β-Diketiminate Ligands: Synthesis and Structural Aspects

“…A vaguely related compound represents the octamolybdenum oxo-pyrazolate cluster containing [Mo 2 O 2 ] 2+ cores bridged by anionic pyrazolates . The IR spectrum of 1 revealed a vibration typical for terminal MoO groups at 959 cm -1 and one due to the Mo−O−Mo stretching vibration at 762 cm -1 , which is in a good agreement with literature compounds. , …”

Mononuclear and Binuclear Cyclopentadienyl Oxo Molybdenum and Tungsten Complexes: Syntheses and Applications in Olefin Epoxidation Catalysis

“…Treatment of 1 with 2 equiv of AllylMgBr led to a diamagnetic microcrystalline yellow solid. 1 H and 13 C NMR spectra of this complex show one set of CpBz resonances, and elemental analysis is consistent with the formulation [Mo-(CpBz)Cl 2 ] 2 (6). The formation of 6 excludes the occurrence of chloride metathesis and suggests that the attack of the Grignard reagent takes place through electrophilic abstraction of the oxo ligand by magnesium, resulting in metal reduction.…”

A Simple Entry to (η5-C5R5)chlorodioxomolybdenum(VI) Complexes (R = H, CH3, CH2Ph) and Their Use as Olefin Epoxidation Catalysts

“…A comparable increase in stability in comparison to compound 5 has also been stated for [Mo(η 5 -C 5 Ph 4 (2,5-dimethoxyphenyl))O 2 Br] 6f and was ascribed to the steric bulk of the ligand. 6f, For prolonged storage complexes 4 and 5 should be kept below room temperature (refrigerator); otherwise they decompose under formation of intractable blue solids 6e. The decomposition of compounds 4 and 5 has been already described in the literature, and it has been stated that light accelerates its decomposition 6e. In this respect it is worth noting that the stability of these complexes increases upon dilution in water-free solvents, a fact that has already been noted for most of the RReO 3 complexes although never properly understood .…”