Haloalkanes as ligands. Spectroscopic and energetic studies of CpMn(CO)2XR

Abstract

6937formation of *py', though energetically less favorable, is faster than formation of py'. In the case of back reactions, the lowest electronic excited states of Irz and py+ are too energetic to be formed in recombination reactions, and inverted behavior is observed.Regardless of the disparity between the *ET and bET reactions, our data demonstrate that inverted driving-force effects can be observed in bimolecular ET reactions. The appearance of inverted effects only for bET reactions may be a feature common to many of the other bimolecular ET systems that have been studied. If formation of electronically excited products is indeed the reason for this disparity, then it should be possible to select donors and acceptors that exhibit inverted driving-force effects in bimolecular photoinduced ET reactions as well. Need).A number of metal complexes containing chloro-, bromo-or iodocarbons ligated through the halide atom have been prepared and, in several instances, characterized by X-ray diffraction.'S2 While many of these complexes involve chelation of a bound ligand, it is evident that coordination of a haloalkane in an intermolecular fashion is possible. ODriscoll and Simon have shown that coordination of an alkyl halide to a transition metal complex is a rapid process, complete within 5 ns of light ab~orption.~ Recent gas-phase studies by Bogdan, Wells, and Weitz have found that the CI-W bond strength in ClFzCCI-W(CO)5 is 19.7 * 0.6

Investigation of the Photochemical Behaviour of Tricarbonyl(cyclopentadienyl)manganese Derivatives with Carbamate Groups

“…The position and intensity of these bands weakly depend on the nature of the solvent (hexane, benzene, ethanol and THF; see the Experimental Section). The parameters of the UV spectra are similar to those for cymantrene derivatives containing THF or alkylamines coordinated to the manganese atom; these cymantrene derivative have an absorption band at about 500 nm assigned to LF bands associated with “d–d” transitions rather than to metal–ligand charge transfer 8,9. This fact provides reason to suppose that in our case, these transitions have the same nature.…”

Ultrafast Ring Closure Energetics and Dynamics of Cyclopentadienyl Manganese Tricarbonyl Derivatives

“…The bimolecular rate constants for the reactions of 1A are the slowest that have been reported for alkane solvent displacement by the ligands studied. For example, the reaction of (C 5 H 5 )Mn(CO) 2 (heptane) with THF (4.4 ± 0.4 × 10 6 M -1 s -1 ) is an order of magnitude faster than the reaction of 1A with THF. Similarly, the rate constants for THF reaction with W(CO) 5 (heptane) and Mo(CO) 5 (heptane) are respectively 1 and 2 orders of magnitude larger .…”

Chromium(vi) oxide–tert-butyl hydroperoxide interactions: evidence for a tert-butylperoxychromium complex and its role in the catalytic oxidation of alcohols

“…9, curve e), only slightly less than in aromatic solvents, seems to indicate that alkanes may interact weakly with this kind of coordinatively unsaturated solvent by their CH bonds, hydrogen bonds 26 or by agostic interactions. 40,41 Based upon the apparent stability of the chromium complex in hexane as shown in Fig. 9, the oxidation of indan-1ol was examined under the usual experimental conditions.…”