Reactions of the tetramethylfulvene ligand coordinated to rhenium with hydrohalic acids and halogens: synthesis of dicarbonyl complexes with a ‘four-legged piano-stool’ structure containing mixed-halide ligands

The new tetramethylfulvene complexes of rhenium (η6-C5Me4CH2)Re(CO)2X, (X=Cl, Br, I) have been synthesized from (η5-C5Me5)Re(CO)2X2 by a two step procedure and fully characterized by elemental analysis, IR and NMR spectroscopies. Reaction of (η6-C5Me4CH2)Re(CO)2X (X=Br, I) with HX′ regenerated the (η5-C5Me5) ligand with the formation of the mixed-halide complexes cis-(η5-C5Me5)Re(CO)2XX′ (X=I, X′=Br; X=I, X′=Cl; X=Br, X′=Cl), whereas, the reaction with halogens (X′2) gave analogous complexes containing a halide substituted tetramethylcyclopentadienyl ligand, cis-(η5-C5Me4CH2X′)Re(CO)2XX′ (X=Br, X′=I; X=I, X′=Br). In both types of complexes the cis stereochemistry have been assigned on the basis of ν(CO) IR intensities and δ(CO) 13C-NMR.4