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Computational and Experimental Studies on the Mechanism of the Photochemical Carbonylation of Group 6 Fischer Carbene Complexes
Author(s) -
Fernández Israel,
Sierra Miguel A.,
GómezGallego Mar,
Mancheño María J.,
Cossío Fernando P.
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400944
Subject(s) - carbene , chemistry , intersystem crossing , photochemistry , singlet state , excited state , dissociation (chemistry) , ketene , carbonylation , molecule , computational chemistry , medicinal chemistry , catalysis , carbon monoxide , organic chemistry , physics , nuclear physics
The photocarbonylation reaction of Group 6 Fischer carbene complexes has been studied by DFT and experimental procedures. The process occurs by intersystem crossing (ISC) from the lowest excited singlet state (S 1 ) to the lowest triplet state (T 1 ), the latter structure being decisive for the outcome of the reaction. Methylenepentacarbonylchromium(0) complexes, alkoxypentacarbonylchromium(0)carbene complexes, and alkoxyphosphinetetracarbonylchromium(0) carbene complexes have coordinatively unsaturated chromacyclopropanone T 1 structures with a biradical character. The evolution of the metallacyclopropanone species occurs by a jump (spin inversion) to the S 0 hypersurface by coordination of a molecule of the solvent, leading to ketene‐derived products in the presence of ketenophiles or reverting to the starting carbene complex in their absence. The T 1 excited states obtained from methylenephosphinetetracarbonylchromium(0) complexes and pentacarbonyltungsten(0)carbene complexes are unable to produce the carbonylation. The reaction with ketenophiles is favored in coordinating solvents, which has been tested experimentally in the reaction of alkoxypentacarbonylchromium(0) complexes and imines.