137253-91-9Relevant academic research and scientific papers
Emission and photochemistry of M(CO)4(diimine) (M = Cr, Mo, W) complexes in room-temperature solution
Manuta, David M.,Lees, Alistair J.
, p. 1354 - 1359 (2008/10/08)
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
Miholova, D.,Vlcek, A. A.
, p. 317 - 326 (2007/10/02)
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
Chemistry of cis-Bis(2,2'-bipyridine)dicarbonyl-molybdenum(0) and -tungsten(0). Substitution Reactions with Phosphorus Donor Ligands and with Isocyanides
Connor, Joseph A.,Overton, Colin
, p. 2397 - 2402 (2007/10/02)
Nucleophilic substitution reactions of cis- (M=Mo or W; bipy=2,2'-bipyridine) by various unidentate (PR3; R=Ph, Bun, or OMe) and bidentate (Ph2PCH2CH2PPh2=dppe) phosphorus and carbon (CNR; R=Et or p-tolyl) donor ligands, L, result in displacement of bipy to produce cis, trans- (L=PR3), cis,cis- (M=Mo, L2=(CNEt)2 or dppe; M=W, L=CNEt>, cis- (M=Mo or W; L=CNC6H4Me-p), and fac- (L=PPh3) depending on the ligand L, temperature, and solvent.Trifluorophosphine reacts with cis- to displace CO and form cis-.Substitution in by isocyanides gives fac- (M=Cr; R=Et or p-tolyl; M=Mo, R=Et) or cis- (R=p-tolyl).The products are characterised by microanalysis and by i.r., (1)H and (31)P n.m.r., electronic, and mass spectroscopy.It is suggested that the formation of cis,trans- may involve a trigonal biprismatic intermediate structure which allows reorganisation to occur simply.The acceptor strength of L in indicated by i.r. , (1)H n.m.r. (bipy ring chemical shifts), and visible (MO -> bipy d?*) spectra, decreases in the order CO > P(OMe)3 > CNEt > PBu3 > bipy, which does not reflect geometrical differences in the disposition of these ligands.
