The Comparative Photochemical Behaviour of Dibenzenechromium and Benzenetricarbonyl Chromium

Abstract

In comparison with (C6H6)Cr(CO)3, (C6H6)2Cr is relatively light stable. The major part of the light energy absorbed by (C6H6)2Cr leads neither to its decomposition or ligand exchange, nor can it be transferred to common low energy triplet acceptors. Internal dissipation of energy, either by rapid conversion to the ground state or by rapid reversible isomerization, must be an important process.In the case of (C6H6)Cr(CO)3, the main pathway to the previously reported lightinduced exchange of benzene involves an intermediate which is suggested to be (benzene)-dicarbonylchromium (1) and not a one-step dissociation of the excited molecule, to give Cr(CO)3 and benzene1b: 1 is also of major importance for the exchange of CO.

Photochemical generation of bis-hexahapto chromium interconnects between the graphene surfaces of single-walled carbon nanotubes

“…The photochemistry of Cr(h 6 -benzene)(CO) 3 is known to be complex, 26,28 but based on the wavelength of the light found to initiate reaction, we postulate the following reaction mechanism (Scheme 2), as Cr(h 6 -benzene)(CO) 3 is known to undergo both arene exchange and CO loss under irradiation with light. 29 The exposure of the SWNT lms to a solution of Cr(h 6 -benzene) 2 in acetonitrile in the presence of room light (ltered through the plexiglass of the glove box), lead to immediate reaction as evidenced by the instantaneous response of the conductivity (Fig. 3c).…”

“…10,15,30,31 Furthermore Cr(h 6 -benzene) 2 is known to be quite stable to irradiation and it does not normally undergo light-induced arene exchange. 29 However, based on the redox potentials of Cr(h 6 -C 6 H 6 ) 2 (reduction potential of Cr(h 6 -C 6 H 6 ) 2…”

A laser flash photolysis, matrix isolation, and DFT investigation of (η6-C6H5Y)Cr(CO)3 (Y=NH2, OCH3, H, CHO, or CO2CH3)

“…= 313 nm) [11]. The quantum yield of arene loss is low, (0.01 for Y = H), and is essentially zero for Y = H when the photolysis is conducted in the presence of added CO [24]. This observation led previous workers to conclude that the arene loss process occurred subsequent to an initial CO loss.…”

Organometallic photochemistry at the end of its first century

“…Frozen matrix techniques have been reviewed [18]. The close relationship between time resolved methods and matrix studies is nicely illustrated in the early literature by flash photochemical studies (uv/visible detection) of (C 6 H 6 )Cr(CO) 3 that revealed the presence of a short lived photointermediate [19]. Subsequent studies by Rest established the existence of the CO-loss photoproducts for this compound as well as for CpMn(CO) 3 and (C 4 H 4 )Fe(CO) 3 using inert gas matrices [20].…”