21240-17-5

Upstream product

• 15668-63-0 (2,2'-bipyridine)tetracarbonylchromium⁽⁰⁾ 
• 603-35-0 triphenylphosphine 

Relevant academic research and scientific papers

Wavelength-dependent photosubstitution and excited-state dynamics of [Cr(CO)4(2,2′-bipyridine)]: A quantum yield and picosecond absorption study

Quantum yields of the photosubstitution of an axial-CO ligand in [Cr(CO)4bpy] by PPh3 were measured as a function of irradiation wavelength, temperature, and solvent. The dependence of quantum yields and of apparent activation energies on the excitation wavelength within the envelope of the metal to ligand charge transfer (MLCT) absorption band points to distinct chemical reactivities for the ligand field (LF) and MLCT excited states. Importantly, it also suggests a photodissociation from higher vibrational levels of directly excited spin-singlet, 1MLCT, electronic excited state(s). This interpretation is corroborated by picosecond transient absorption spectra which show a presence of a short-lived (tens of picoseconds) transient, identified with a 1MLCT excited state, and a long-lived (≥100 ns) transient assigned as a spin-triplet 3MLCT state. Spectroelectrochemical results indicate a resemblance between the 1MLCT state and the one-electron reduced species, [Cr(CO)4bpy]-. Comparison of the picosecond spectra measured under 532 (MLCT) and 355 nm (LF) excitation shows that the electronic relaxation of LF states bypasses the 1MLCT excited state(s), 1LF(reactive) → 3LF(reactive) → 3MLCT(slowly) → 1ground state, whereas the relaxation of 1MLCT state(s) follows the 1MLCT(reactive) → 3MLCT(slowly) → 1ground state pathway.

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.

ELECTRODE-CATALYZED SUBSTITUTION OF M(CO)4bipy (M=Cr, Mo, W) INITIATED BY REDUCTION

One CO group is labilized and substituted by triphenylphosphine in radical anions formed by the electrochemical reduction of M(CO)4bipy=2,2-bipyridyl; M=Cr, Mo, W).The reaction proceeds as an electrode-catalyzed process.It is shown that the release of the

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).