Intermolecular C−Cl Activation Reaction of (η⁵-C₅R₅)Re(CO)₃ (R = H, Me) with Pentachlorobenzene: X-ray Structure of <i>cis</i>- and <i>trans</i>-(η⁵-C₅Me₅)Re(CO)₂(2,3,4,5-C₆HCl₄)Cl and Its Conversion to (η⁶-C₅Me₄CH₂)Re(CO)₂(2,3,4,5-C₆HCl₄)

Abstract

Photochemical reaction of (η5-C5R5)Re(CO)3 (R = H, Me) with pentachlorobenzene (λ = 350 nm, hexane solution) yields trans-(η5-C5R5)Re(CO)2(2,3,4,5-C6HCl4)Cl (trans-1, R = Me; 2, R = H) formed by insertion of the fragment (η5-C5R5)Re(CO)2 into the C−Cl bond of C6HCl5. Complex trans-1 converts to cis-(η5-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 ν(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 (η6-C5Me4CH2)Re(CO)2(2,3,4,5-C6HCl4), 3.