60105-80-8Relevant academic research and scientific papers
Laser flash photolysis and matrix isolation studies of Ru[R2PCH2CH2PR2]2H 2 (R = C2H5, C6H5, C2F5): Control of oxidative addition rates by phosphine substituents
Cronin, Leroy,Nicasio, M. Carmen,Perutz, Robin N.,Peters, R. Greg,Roddick, Dean M.,Whittlesey, Michael K.
, p. 10047 - 10054 (1995)
The photochemistry of ruthenium hydrides Ru(depe)2H2, cis-Ru(dppe)2H2 and cis-Ru(dfepe)2H2 [depe = Et2PCH2CH2PEt2, dppe = Ph2PCH2CH2PPh2, dfepe = (C2F5)2PCH2CH2P(C 2F5)2] has been studied by matrix isolation at 12 K and laser flash photolysis at ambient temperature. Both techniques yield the 4-coordinate 16-electron RuP4 species. The ethyl and phenyl species, Ru(depe)2 and Ru(dppe)2, exhibit very similar UV-visible spectra to Ru(dmpe)2 [Ru(depe)2 475, 580, 735 nm; Ru(dppe)2 465, 550, 760 nm in solution]. The spectrum of Ru(dfepe)2 is blue-shifted relative to the others (380, 450, 620 nm). The comparison of the spectra with that of [Rh(dppe)2]+ conclusively establishes a square-planar structure for Ru(depe)2 and Ru(dppe)2. The rates of reaction with added ligands are extremely sensitive to substituent. The rate constants for reaction with H2 are Ru(dfepe)2 2.0 × 105, Ru(dppe)2 2.4(2) × 107, Ru(depe)2 4.0(4) × 108 dm3 mol-1 s-1 compared to 6.8 × 109 dm3 mol-1 s-1 for Ru(dmpe)2. For reaction with CO, the rate constants are Ru(dfepe)2 1.1 × 104, Ru(dppe)2 1.0(2) × 107, Ru(depe)2 9.1(7) × 107 dm3 mol-1 s-1 compared to 4.6 × 109 dm3 mol-1 s-1 for Ru(dmpe)2. Thus reactivity increases in the order Ru(dfepe)2 2 2 2 with an overall span of a factor of 34 000 for reaction with H2 and 418 000 for reaction with CO. The rate constants for reaction of Ru(depe)2 with C2H4 and Et3SiH, and for reaction of Ru(dppe)2 with C2H4 have also been determined.
Photochemical pump and NMR probe: Chemically created NMR coherence on a microsecond time scale
Torres, Olga,Procacci, Barbara,Halse, Meghan E.,Adams, Ralph W.,Blazina, Damir,Duckett, Simon B.,Eguillor, Beatriz,Green, Richard A.,Perutz, Robin N.,Williamson, David C.
, p. 10124 - 10131 (2014/08/05)
We report pump-probe experiments employing laser-synchronized reactions of para-hydrogen (para-H2) with transition metal dihydride complexes in conjunction with nuclear magnetic resonance (NMR) detection. The pump-probe experiment consists of a single nanosecond laser pump pulse followed, after a precisely defined delay, by a single radio frequency (rf) probe pulse. Laser irradiation eliminates H2 from either Ru(PPh3) 3(CO)(H)2 1 or cis-Ru(dppe)2(H)2 2 in C6D6 solution. Reaction with para-H2 then regenerates 1 and 2 in a well-defined nuclear spin state. The rf probe pulse produces a high-resolution, single-scan 1H NMR spectrum that can be recorded after a pump-probe delay of just 10 μs. The evolution of the spectra can be followed as the pump-probe delay is increased by micro- or millisecond increments. Due to the sensitivity of this para-H2 experiment, the resulting NMR spectra can have hydride signal-to-noise ratios exceeding 750:1. The spectra of 1 oscillate in amplitude with frequency 1101 ± 3 Hz, the chemical shift difference between the chemically inequivalent hydrides. The corresponding hydride signals of 2 oscillate with frequency 83 ± 5 Hz, which matches the difference between couplings of the hydrides to the equatorial 31P nuclei. We use the product operator formalism to show that this oscillatory behavior arises from a magnetic coherence in the plane orthogonal to the magnetic field that is generated by use of the laser pulse without rf initialization. In addition, we demonstrate how chemical shift imaging can differentiate the region of laser irradiation thereby distinguishing between thermal and photochemical reactivity within the NMR tube.
