The reactions of (η 6 -arene)Mo(CO) 2 (Sol) and M(CO) 5 (Sol) with CO have been studied in a range of alkane solvents (Sol), and the kinetic and activation parameters have been determined (M ) Cr, Mo, or W). For M ) Cr the ∆H q is constant (22 ( 2 kJ mol -1 ), while the ∆S q term becomes less negative as the alkane chain length increases. For the larger metals the variation in kinetic and activation parameters is less significant. Solvent displacement by CO involves an interchange mechanism for the Cr system, while for Mo or W complexes the mechanism is more associative in character. The photochemistry of (η 6 -arene)Mo(CO) 3 (arene ) benzene, mesitylene, p-xylene, or hexamethylbenzene) compounds was investigated by laser flash photolysis, supported by matrix isolation and time-resolved infrared spectroscopy (TRIR). In contrast to the behavior to the analogous (η 6 -arene)Cr-(CO) 3 , it is found that the efficiency for photochemical expulsion of CO from (η 6 -mesitylene)-Mo(CO) 3 is markedly wavelength dependent (Φ CO ) 0.587, 0.120, and 0.053 at 266, 313, and 334 nm, respectively).

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Photodissociation of gaseous CH3COSH at 248 nm by time-resolved Fourier-transform infrared emission spectroscopy: Observation of three dissociation channels J. Chem. Phys. 138, 014302 (2013); 10.1063/1.4768872 Gas-phase photodissociation of CH3COCN at 308 nm by time-resolved Fourier-transform infrared emission spectroscopy J. Chem. Phys. 136, 044302 (2012); 10.1063/1.3674166 I. Three-center versus four-center HCl-elimination in photolysis of vinyl chloride at 193 nm: Bimodal rotational distribution of HCl (v7) detected with time-resolved Fourier-transform spectroscopy

The photochemistry of (η6-2,6-X2C5H3N)Cr(CO)3 was investigated both in low-temperature matrices (X = H or (CH3)3Si) and in room-temperature solution (X = H, CH3, or (CH3)3 Si). Room-temperature photolysis (λexc > 410 nm) in CO-saturated methanol or acetonitrile produced (η1-2,6-X2C5H3N)Cr(CO)5 which subsequently formed Cr(CO)6 in a secondary photochemical process (X = H or CH3). The efficiency of pentacarbonyl formation is lower in CO-saturated cyclohexane and follows the order X = H > X = CH3. Photolysis in low-temperature matrices resulted in an η6 to η1 pyridine ring-slippage (λexc = 460 nm; X = H). Visible irradiation in a CO-doped methane matrix produced (η1-C5H5N)Cr(CO)5, while in an N2 matrix fac-(η1-C5H5N)(N2)2Cr(CO)3 is formed. Irradiation with λexc = 308 nm produced both the ring-slippage product and also the CO-loss product (η6-C5H5)Cr(CO)2, which in a N2 matrix is trapped as (η6- C5H5N)Cr(CO)2(N2). Time-resolved infrared spectroscopy in cyclohexane revealed only the CO-loss product (λexc = 308 nm; X = H). The apparent difference in room-temperature and low-temperature photochemistry is explained by a rapid regeneration of (η6-C5H5N)Cr(CO)3 from the η1-intermediate. This explanation was supported by laser flash photolysis experiments (λexc = 355 nm) in CO-saturated cyclohexane (Sol), where the recovery of the (η6-C5H5N)Cr(CO)3 absorption follows a biphasic time profile, whereby the faster process was assigned to the η1 to η6 transformation and the slower to the reaction of (η6-C5H5N)Cr(CO)2(Sol) with CO. Crystals of (η6-2,6-(CH3)2C5H3N)Cr(CO)3 and (η6-2,6-((CH3)3Si)2C5H3N)Cr(CO)3 were characterized by X-ray diffraction.

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