Intermolecular C-Cl activation reaction of (pi(5)-C5R5)Re(CO)(3) (R = H, Me) with pentachlorobenzene: X-ray structure of cis- and trans-(eta(5)-C5Me5)Re(CO)(2)(2,3,4,5-C6HCl4)Cl and its conversion to (eta(6)-C5Me4CH2)Re(CO)(2)(2,3,4,5-C6HCl4)

Abstract

Photochemical reaction of (eta(5)-C5R5)Re(CO)3 (R = H, Me) with pentachlorobenzene (lambda = 350 nm, hexane solution) yields trans-(eta(5)-C5R5)Re(CO)(2)(2,3,4,5-C6HCl4) (trans-1, R = Me; 2, R = H) formed by insertion of the fragment (eta(5)-C5R5)Re(CO)(2) into the C-Cl bond of C-6-HCl5. Complex trans-1 converts to cis-(eta(5)-C5Me5)Re(CO)(2)(2,3,4,5-C6HCl4)Cl (cis-1) in MeCN. The stereochemistry of both isomers has been assigned from examination of nu(CO) IR intensities and is supported by an X-ray structure determination of both complexes. A pure sample of either trans-1 or cis-1 dissolved in organic solvents produces an equilibrium mixture. In nonpolar solvents trans-1 is favored, whereas cis-1 is more stable in polar solvents, A mixture of cis-1 and trans-1 in CH2Cl2 solution reacts on silica gel to produce the new tetramethylfulvene complex (eta(6)-C5Me4CH2)Re(CO)(2)(2,3,4,5-C6HCl4), 3.