134736-63-3Relevant academic research and scientific papers
EPR study of photochemical reactions of fac- and mer-[Cr(CO)3(η1-L2)(η2-L 2)]+ (L2 = bidentate phosphine, arsine, or phosphonite ligand)
Rieger, Anne L.,Rieger, Philip H.
, p. 5868 - 5873 (2008/10/08)
Rearrangement of fac-[Cr(CO)3(η2-L2)(η1-L 2)]+ to mer-(CO)3(η2-L2)(η1-L2 )]+ (L2 is a bidentate phosphine or arsine ligand) is a rapid thermally activated process. Loss of CO from mer-[Cr(CO)3(η2-L2)(η1-L 2)]- to form trans-[Cr(CO)2(η2-L2)2]- is shown to be a clean photochemical process, perhaps the first example of a quantitative photochemical transformation for a Cr(I) complex. The bidentate phosphonite ligand, L2 = (MeO)2PCH2CH2P(OMe)2, behaves quite differently: fac-[Cr(CO)3(η2-L2)(η1-L 2)]- undergoes photochemical loss of CO to form a five-coordinate complex which converts slowly via thermal activation to trans[Cr(CO)2(η2-L2)2]+ .
Chemical and electrochemical oxidation of mer/fac-Cr(CO)3(η1-L-L)(η2-L-L) containing a pendant donor atom: ESR studies of the cations mer-[Cr(CO)3(η1-L-L)(η2-L-L)] + and trans-[Cr(CO)2(η2-L-L)2]+ (L-L = bidentate group 15 ligand)
Bagchi, Ramen N.,Bond, Alan M.,Colton, Ray,Creece, Ian,McGregor, Katherine,Whyte, Tania
, p. 2611 - 2615 (2008/10/08)
Reactions between Cr(CO)3(C7H8) and Ph2PCH2CH2AsPh2 (ape) and Ph2AsCH2CH2AsPh2 (dae) give mer-Cr(CO)3(η1-ape)(η2-ape) and fac-Cr(CO)3(η1-dae)(η2-dae), respectively. Phosphorus-31 NMR studies show that the monodentate ape ligand is coordinated through phosphorus. Upon electrochemical oxidation in dichloromethane (0.1 M Bu4NClO4) at platinum electrodes, mer-Cr(CO)3(η1-ape)(η2-ape) is reversibly oxidized to mer-[Cr(CO)3(η1-ape)(η2-ape)] + whilst fac-Cr(CO)3(η1-dae)(η2-dae) gives fac-[Cr(CO)3(η1-dae)(η2-dae)] +, which rapidly isomerizes to mer-[Cr(CO)3(η1-dae)(η2-dae)] +. In addition, for each complex a further irreversible 1-electron process is observed at very positive potentials. ESR studies on several mer-[Cr(CO)3(η1-L-L)(η2-L-L)] + cations (L-L = bidentate group 15 ligand), electrochemically generated in a sealed tube within the ESR microwave cavity, show that they decompose very slowly to trans-[Cr-(CO)2(η2-L-L)2]+. The rate of decomposition to trans-[Cr(CO)2(η2-L-L)2]+ is faster in a nonsealed tube with nitrogen purging. The ESR spectra of the tricarbonyl and dicarbonyl 17-electron cations show both phosphorus and arsenic hyperfine structure with very similar values for the coupling constants. Chemical oxidation of mer/fac-Cr(CO)3(η1-L-L)(η2-L-L) with an equimolar (or greater) quantity of AgClO4 also gives mer-[Cr(CO)3(η1-L-L)(η2-L-L)] +. In one case, (L-L = Ph2PCH2PPh2(dpm)), when 0.5 molar equiv of AgClO4 is used, a diamagnetic intermediate silver complex is identified by phosphorus-31 NMR spectroscopy. In the presence of excess of AgClO4, the rate of decomposition of mer-[Cr(CO)3(η1-L-L)(η2-L-L)] + to trans-[Cr(CO)2(η2-L-L)2]+ is greatly enhanced, further confirming that the silver ion is a noninnocent oxidant when a pendant donor atom is present.
