Synthesis and reactivity of η5-tetramethylcyclopentadienyl-propenyl rhenium complexes: Molecular structure of [(η5:η2-C5Me4CH2CH=CH2)Re(CO)2]

The fulvene complexes [(eta(6)-C5Me4CH2)Re(CO)(2)(R)] (1a, R=I; 1b, R=C6F5) react at the exocyclic methylene carbon with a vinylmagnesium bromide solution to produce the anionic species [(eta(5)-C5Me4CH2CH=CH2)Re(CO)(2)(R)] . Protonation with HCl at 0 degrees C produces the hydride complexes [trans-(eta(5)-C5Me4CH2CH=CH2)Re(CO)(2)(R)(H)] (2a, R=I; 2b, R=C6F5). Thermolysis of an hexane solution of the iodo-hydride (2a) under a CO atmosphere yields the complex [(eta(5)-C5Me4CH2CH=CH2)Re(CO)(3)] (3) and [Re(CO)(5)I] as by-product. Thermolysis of 2b produced three new products, mainly the chelated complex [(eta(5):eta(2)-C5Me4CH2CH=CH2)Re(CO)(2)] (4) and complex 3, with a non-coordinated ole. n group, in moderated yield, and traces of [Re(CO)(5)(C6F5)]. Thermolysis of an hexane solution of 2 in presence of an excess of PMe3, afforded the phosphine derivative [(eta(5)-C5Me4CH2CH=CH2)Re(CO)(2)(PMe3)] (5). All the complexes were characterized by IR, H-1, C-13 and P-31 NMR spectroscopies and mass spectrometry. The molecular structure of 4 has also been determined. The molecule exhibits a formal three-legged piano-stool structure, with two CO groups, and the third position corresponding to the g2- coordination of the propenyl side arm of the eta(5)-C5Me4 ring. (C) 2009 Elsevier B.V. All rights reserved.