METAL-STABILIZED CARBANIONS VI. FORMATION OF SOME ARYLMETHYL AND DIBENZOTROPENYL CARBANIONS COMPLEXED WITH TRICARBONYLCHROMIUM. A KINETIC AND A 13C NMR STUDY

Article abstract of DOI:10.1016/0022-328X(84)85055-X

Rate constants have been measured for the α-metallation of some arylmethanes, of 5H-dibenzocycloheptene and its dihydro derivative, free and complexed with tricarbonylchromium, by potassium hydride in tetrahydrofuran in the presence of 18-crown-6 ether.The stable solutions of the complexed anions have been studied by 13C NMR spectroscopy.With the free ligands the kinetic acidity depends upon the structure to a great extent, but in the corresponding complexes the rates of metallation do not vary appreciably.On the basis of the 13C chemical shift data a close similarity is suggested between the electronic structures of the arylmethyl and dibenzotropenyl anions which would account for their very similar metallation rates.