Laser Photolysis Studies of the Reaction of Chromium(III) Octaethylporphyrin Complex with Triphenylphosphine and Triphenylphosphine Oxide

Abstract

The photoreaction of the chromium(III) octaethylpoprhyrin complex, [Cr(OEP)(Cl)(L)] (L = H2O, Py, OPPh3), in dichloromethane was studied using laser flash photolysis technique. Laser irradiation causes the generation of a coordinately unsaturated intermediate [Cr(OEP)(Cl)], which reacts with ligands in solution to give the parent complex, [Cr(OEP)(Cl)(L)], or a transient species, [Cr(OEP)(Cl)(H2O)], when L = Py or OPPh3. Once produced [Cr(OEP)(Cl)(H2O)] eventually exchanges the axial H2O ligand with L to regenerate [Cr(OEP)(Cl)(L)]. The kinetics of the axial ligand substitution reaction was followed spectrophotometrically, and the ligand-concentration dependence of the ligand exchange rate revealed that the reaction occurs via a limited dissociative mechanism. The photoreaction of [Cr(OEP)(Cl)(OPPh3)] containing excess PPh3 in the bulk solution leads to the unfavorable coordination of the PPh3 molecule to the chromium ion to give a transient complex, [Cr(OEP)(Cl)(PPh3)]. The dynamic and thermodynamic properties of [Cr(OEP)(Cl)(PPh3)] in solution are discussed on the basis of the kinetic parameters of the dissociation and association reactions of the PPh3 ligand together with the steric aspect of the molecular structure of the related complexes.

Role of the Cocatalyst in the Copolymerization of CO2 and Cyclohexene Oxide Utilizing Chromium Salen Complexes

“…It should be stated parenthetically that all attempts to grow single crystals of adducts of catalytically active phosphines with 1 were unsuccessful. Similarly, in a recent report efforts to grow single crystals of chromium(III) octaehtylporphyrin, Cr(OEP)Cl, with PPh 3 failed, whereas crystals of its OPPh 3 adduct were readily obtained from OPPh 3 and its molecular structure was determined 19 X-ray crystal structure of 3·O  PCy 3 .…”

Ferromagnetic coupling in d1–d3 linear oxido-bridged heterometallic complexes: ground-state models of metal-to-metal charge transfer excited states

“…2,5 When comparing bimetallic 1 with (omtaa) VvO, the VvO bond length increases by about 0.03 Å (1.612 Å 25,31 to 1.640 Å) and the V-N length is shortened by about 0.03 Å (2.028 Å to 1.996 Å). A Cr-O distance of 1.964 Å is observed, which is shorter than that of some weakly bonded O-donor Lewis bases 32 but significantly longer than other unsupported oxido bridged complexes. 2,5,15 This explains our observation that bimetallic 1 can dissociate in solution.…”

meso-Porphyrinylphosphine Oxides: Mono- and Bidentate Ligands for Supramolecular Chemistry and the Crystal Structures of Monomeric {[10,20-Diphenylporphyrinatonickel(II)-5,15-diyl]-bis-[P(O)Ph2] and Polymeric Self-Coordinated {[10,20-Diphenylporphyrinatozinc(II)-5,15-diyl]-bis-[P(O)Ph2]}

“…Similar compounds in the literature show bond angles between 140°and 180°for analogous phosphine oxide coordinating groups, so this situation is not considered abnormal. 56 The phenyl rings of the diphenylphosphine oxide groups bound to zinc are sandwiched by alternating pairs of porphyrin rings in the chain. There are intrachain aryl-aryl interactions of the edge-to-face type between the edges of the diphenylphosphine oxide phenyl rings [C(39)-C(44) and C(45)-C(50)] and the faces of the aromatic porphyrin rings (CH edge ‚‚‚Porphyrin plane contact distances between 2.65 and 2.80 Å).…”

“…Adjacent chains are connected to one another by vertex-to-face-type interactions between the meso phenyl rings comprising C(33)-C(38) (vertex) and the diphenylphosphine oxide phenyl rings comprising C(21)-C(26) (face) (CH vertex ‚‚‚ Ph plane ) 3.10 Å) that propagate the lattice in the c direction. Also, connecting adjacent chains in the c direction are offset face-to-face π-stacking interactions between meso phenyl rings [C(51)-C (56)]. Each ring is involved in two such interactions, with interaction distances Ph plane ‚‚‚Ph plane ) 3.53 and 3.61 Å, which form a continuous thread, normal to the ac plane, that propagates with crystallographic inversion symmetry.…”