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An investigation of the photochemistry of organometallic metal carbonyl compounds by transient spectroscopic techniques
McGrath, I. M
(ri6-benzene)Cr(CO)2(S) was unequivocally identified as an intermediate in the flash photolysis of (Ti^-benzene)Cr(CO)3 in alkane solution by a combination o f UV/vis and TRIR studies. A range of substituted (r|6-arene)Cr(CO)3 complexes was synthesised, where arene = toluene, p-xylene, 1,3,5-mesitylene or C^Meg, and the effect of increased methylation of the arene nng upon the reactivity of the (r|6- arene)Cr(CO)2(S) intermediate was investigated. The rate of reaction of this species with CO increased upon methyl substitution of the arene and upon changing the solvent from cyclohexane to alkane. The enthalpies o f activation for this reaction were constant at 25 ± 2 kJ mol‘ 1 while the entropy of activation increased with increased methyl substitution. The rate of reaction of this species with parent to produce the dinuclear complex (r|6-arene)Cr(CO)2(H.CO)Cr(CO)2(T|6-arene) was noted in the benzene case Complexes attributed to the binding of solvent impurities were ascribed to some of the primary and secondary photochemistry observed. The heterobimetallic dinuclear complex Mn(CO)4-r]3-C3H4-T|6-CgH5-Cr(CO)3 and its substituent Mn(CO)4*T|3-C3H4-C6H5 were investigated by laser flash photolysis. The formation of an acyclic pentadienyl complex is proposed in both cases, by means of a facile r|3 to hapticity change of the allyl group. In the dinuclear complex this reaction occurs independently of both parent and CO concentration. The laser flash photolysis of (t|5-C5H5)V(CO)4 was studied at excitation wavelengths o f 266nm and 355nm. The experimental results were extremely irreproducible. The observation of both (r|5-C5H5)V(CO)3(S) and C5H5)V(CO)5 was suggested. The observation of a long-lived product in solution Xlll was attributed to the formation of (r|5-C5H5)2V2(CO)5 The results did not permit the proposal of a reaction scheme.
Keyword(s): Chemistry; Metal catalysts; Catalysts Testing
Publication Date:
1993
Type: Other
Peer-Reviewed: Unknown
Language(s): English
Contributor(s): Long, Conor
Institution: Dublin City University
Citation(s): McGrath, I. M (1993) An investigation of the photochemistry of organometallic metal carbonyl compounds by transient spectroscopic techniques. PhD thesis, Dublin City University.
Publisher(s): Dublin City University. School of Chemical Sciences
File Format(s): application/pdf
Related Link(s): http://doras.dcu.ie/19044/1/I_M_McGrath.pdf
First Indexed: 2013-08-29 05:07:16 Last Updated: 2019-02-09 06:30:50