15492-75-8

Upstream product

• 14168-63-9 [Cr(CO)4(1,10-phenanthroline)] 
• 603-35-0 triphenylphosphine 
• 66-71-7 1,10-Phenanthroline 

Relevant academic research and scientific papers

Systematic Tuning of the Photosubstitution Mechanism of M(CO)4(1,10-phenanthroline) by Variation of the Metal, Entering Nucleophile, Excitation Wavelength, and Pressure

The photosubstitution reactions of M(CO)4(phen) (M = Cr, Mo, W; phen = 1,10-phenanthroline) with PR3 (R = Me, Bun, Ph) to form M(CO)3(PR3(phen) were studied as a function of excitation wavelength, entering nucleophile concentration, and pressure. Ligand field photolysis in general results in a dissociative substitution mechanism. whereas charge-transfer photolysis can, depending on the nature of M and PR3, proceed according to an associative mechanism. The chemical and physical variables studied result in a systematic tuning of the photosubstitution mechanism. Nucleophile concentration, excitation wavelength, and pressure dependencies reveal unique mechanistic information. The results are discussed in reference to available literature data, and a complete mechanistic analysis is presented.

Photo-substitution reactions of Cr(CO)4(1,10-phenanthroline). Mechanistic information from entering nucleophile, irradiation wavelength and pressure dependences

Quantum yields for the photo-substitution of Cr(CO)4phen (phen = 1,10-phenanthroline) by PMe3 and PPh3 (L) to produce Cr(CO)3(L)phen were determined as a function of nucleophile concentration, irradiation wavelength and pressure. The results show that LF photolysis is decelerated significantly on increasing pressure, which is in line with a limiting dissociative mechanism. There is a steady decrease in the corresponding volume of activation on increasing the irradiation wavelength from 366 to 546 nm. The results obtained from MLCT photolysis indicate that ligand substitution proceeds according to a dissociative interchange (Id) mechanism. The results for PMe3 and PPh3 are rather similar and demonstrate that relatively little bond formation occurs with the entering nucleophile during MLCT photolysis.

Emission and photochemistry of M(CO)4(diimine) (M = Cr, Mo, W) complexes in room-temperature solution

Electronic absorption, emission, and photochemical data are reported for a series of M(CO)4L complexes, where M = Cr, Mo, or W and L = 2,2′-bipyridine, 1,10-phenanthroline, or a derivative diimine ligand. Low-energy ligand field (LF) and intense metal-to-ligand charge-transfer (MLCT) transitions are observed in the electronic absorption spectra. The energy positions of the MLCT transitions are extremely sensitive to the nature of ligand substituent and solvent medium. Each complex exhibits dual emission features at 298 K in the 500-850-nm region and two low-lying M → π*(L) transitions are implicated in the radiative decay process. Quantum efficiencies for photosubstitution (φ) have been determined following excitation into the low-lying excited states. The photoreaction efficiences depend substantially on the irradiation wavelength; e.g., for W(CO)4(bpy) in benzene LF excitation at λ = 395 nm yields φ = 1.2 × 10-2, whereas MLCT excitation at λ = 514 nm yields φ = 5.4 × 10-5. Photosubstitution data indicate that a LF state is largely responsible for the photochemistry in these M(CO)4L complexes. The photoefficiencies following MLCT excitation at 514 nm are only slightly temperature-dependent, indicating that either the MLCT state is intrinsically photoactive or another excited state lies close in energy and contributes to the photochemistry. The suggestion of photoreaction from the low-lying LF triplet state (1A → 3E) is discussed. An excited-state scheme relating the photochemical and emission data is presented.

Mixed complexes of group VIb metal carbonyls

Forty-nine new mixed derivatives - which contain two different noncarbonyl substituent groups - of the group VIb metal carbonyls are reported. These are of the types M(CO)3X2Y and M(CO)2X2Y2 where M = Cr, Mo, W; X2 = 2,2′-dipyridyl (dipy) or o-phenanthroline (phen); and Y = various monodentate Lewis bases. Carbonyl stretching frequencies for many derivatives containing strongly π-accepting Y ligands yield complex Cotton-Kraihanzel force constants; real force constants may be obtained if the two physically different cis-CO-CO interactions are differentiated in a physically reasonable way. Evidence is presented that N,N′-dimethylformamide (DMF) and acetamide exhibit normal coordination through oxygen in the complexes Mo(CO)3(phen)(DMF) and Mo(CO)3(phen)(acetamide).