TpRe complexes synthesis

Metal fragments of the form (TpRe(CO)(L), in which L = Melm or NH3, have the ability to bind substituted benzenes in an 2-fashion. The fragment having L = Melm has seen more application because of difficulties associated with the synthesis and isolation of aromatic complexes having L = NH3. Anisoles, phenols, and naphthalenes all form thermally stable -complexes when stirred in excess (10-25 equiv.) with TpRe(CO)(MeIm)( /2-benzene) in THF. The complexes are typically isolated by precipitation from hexanes. The benzene complex can be prepared by direct reduction of the Re(III) precursor, TpRe(MeIm)(Br)2, with Na° in benzene under one atmosphere of CO [35]. 

Schrock and co-workers have described the synthesis of a rhenium neopentyli-dyne complex containing the tris(pyrazolyl)borate ligand from Re( = C Bu) (CH2 Bu)3(OTf). Treatment of this complex with excess pyridine afforded the colourless, six-coordinate rhenium neopentylidene/neopentylidyne complex Re( = C Bu)(OTf)(CH2 Bu)( = CH Bu)(py)2], which was subsequently subject to ligand substitution by Na[Tp], producing the thermally stable, 18-electron complex TpRe( = C Bu)(CH2 Bu)( = CH Bu) (Scheme 27). Rhenium is one of the three... 

Scheme 32. Synthesis of TpRe(CO)(MeIm)( / -aromatic) complexes.

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