- THE GENERATION IN SOLID CO OF THE RADICAL Mn(CO)5
-
The radical Mn(CO)5 is generated by the photolysis of HMn(CO)5 in a low temperature solid CO matrix.It is characterized by IR spectroscopy, including isotopic studies, and it is shown to have a visible absorption band at ca. 800 nm, close to that assigned to Mn(CO)5 in room-temperature studies.
- Church, S. P.,Poliakoff, M.,Timney, J. A.,Turner, J. J.
-
-
Read Online
- Photochemical bond homolysis in a novel series of metal-metal bonded complexes Ru(E)(E′)(CO)2(iPr-DAB)
-
Photochemistry of the complexes trans,cis-Ru(E)(E′)(CO)2(iPr-DAB) (E = Cl, SnPh3, PbPh3, Mn(CO)5, Re(CO)5, Me; E′ (depending on E) = SnPh3, PbPh3, GePh3, Mn(CO)5, Re(CO)5) was found to be strongly dependent on the combination and characters of the axial ligands E and E′. Except for Ru(Cl)(SnPh3)(CO)2(iPr-DAB) and Ru(Cl)(PbPh3)(CO)2(iPr-DAB) which are nearly unreactive, one of the Ru-E/E′ bonds is split homolytically upon irradiation into the lowest-energy absorption band of the complex. For Ru(SnPh3)2(CO)2(iPr-DAB), this reaction occurs from a thermally equilibrated 3σπ* excited state with a rate constant of 2.3 × 105 s-1 and a temperature-dependent quantum yield (Ea = 1450 cm-1). The unselective Ru-Ge (60%) and Ru-Sn (40%) bond homolysis of Ru(SnPh3)(GePh3)(CO)2-(iPr-DAB) follows the same mechanism. On the other hand, bond homolysis is much faster (?108 s-1) for complexes which contain Ru-Me, Ru-Mn or Ru-Re bonds. Bond homolysis in these species is highly selective, since only Ru-Me, Ru-Mn and Ru-Re bond splitting was observed for Ru(Me)(SnPh3)(CO)2(iPr-DAB), Ru(SnPh3)(Mn(CO)5)(CO)2(iPr-DAB) and Ru(SnPh3)(Re(CO)5)(CO)2(iPr-DAB), respectively. The photoproduced [Ru(E)(CO)2(iPr-DAB)]· radicals were detected by time resolved UV-Vis spectroscopy on a timescale 10 ns-100 μs. The [Ru(SnPh3)(CO)2(iPr-DAB)]· radical was also characterised by EPR in the form of its adduct with PPh3. Depending on the solvent used, they either dimerise or abstract a chlorine atom from the solvent to produce Ru(Cl)(E)(CO)2(iPr-DAB).
- Aarnts, Maxim P.,Stufkens, Derk J.,Vlcek Jr., Antonin
-
-
- Properties and dynamics of the σ(M′-Re) π* excited state of photoreactive dinuclear LnM′-Re(CO) 3 (α-diimine) (LnM′ = Ph3Sn, (CO)5Mn, (CO)5Re; α-diimine = bpy′, iPr-PyCa, iPr-DAB) complexes studied by time-resolved emission and absorption spectroscopies
-
The photophysics and photochemistry of the metal-metal bonded complexes LnM′Re(CO)3(α-diimine) (LnM′ = Ph3Sn, (CO)5Re, (CO)5Mn; α-diimine = bpy′, iPr-PyCa, iPr-DAB) have been studied. According to the time-resolved emission (80 K) and absorption (room temperature) spectra, the lowest excited state has a 3σ (M′-Re) π* character. It is a bound state, which can only be populated by surface crossing from optically excited MLCT states. Homolysis of the metal-metal bond from the σπ* state is promoted by nucleophilic and chlorinated solvents. Exceptional in this respect is the complex Ph3SnRe(CO)3(bpy′), which is nearly photostable in non-chlorinated solvents. The lifetime of the 3σπ* state decreases in the order α-diimine = bpy′ > iPr-PyCa > iPr-DAB > pAn-DAB. This trend is mainly determined by the energy gap law. The LnM′ dependence is more complicated because of an additional deactivating effect of an excited state distortion which depends on LnM′. At 80 K, the lifetime is determined by the weak coupling to the ground state; at room temperature by dissociation of M′-Re (with the exception of Sn-Re).
- Rossenaar, Brenda D.,Lindsay, Elspeth,Stufkens, Derk J.,Vl?ek Jr., Antonín
-
-
- Infrared Chemiluminescence Study of the F Atom + HMn(CO)5 Reaction
-
The HF infrared chemiluminescence from the reaction of F atoms with HMn(CO)5 has been observed in a flow reactor.The nascent HF vibrational distribution is P1-P4=0.20:0.44:0.35:ca. 0.01, and v(HF)> is 0.31 for P0 assigned as zero.The HF(ν,J) populations do not extend to the thermochemical limit, and v(HF) is abnormally low relative to typical H abstraction reaction by F atoms.The H abstraction reaction from toluene-d5 was reinvestigated to provide a reference for a system yielding HF(ν) and a product with a large radical stabilization energy.The D0(CH3C6D4-D) was estimated as -1, based upon the highest observed DF(ν,J) level.
- Wategaonkar, S. J.,Setser, D. W.
-
-
- STERIC EFFECTS OF PHOSPHINE LIGANDS ON THE PHOTOCHEMISTRY PF Mn2(CO)10
-
The photochemistry of Mn2(CO)10 in the presence of phosphine ligands has been investigated.Steric hindrance by the phosphine molecules influences the products of the photolysis reaction.With ethyldiphenylphosphine disubstituted symmetrical species are obt
- Busetto, C.,Mattucci, A. M.,Cernia, E. M.,Bertani, R.
-
p. 183 - 188
(2007/10/02)
-