Photochemistry of rhodium(I) olefin complexes containing the (hydro)tris(pyrazolyl)borate ligand

The photoisomerisation (lambda=400nm) of [Tp(Me2)Rh (eta(4)-1,5-COD)] (1), (Tp(Me2)=hydrotris(3,5-dimethyl)pyrazolyl berate, 1,5-COD=1,5-cyclooctadien e) to [Tp(Me2)Rh (eta(4)-1,3-COD)] (2) is reported. The photoreaction is an intramolecular (3,4) hydrogen shift of the coordinated 1,5-COD possibly in volving an allylrhodium(III) intermediate. The selective photolysis of comp lex 2 with 336 nm light causes the dissociation of 1,3-COD forming the orga nometallic fragment {Tp(Me2)Rh} (A) as its primary photoproduct. Fragment A is a versatile entry point in the photochemical preparation of new hydride Rh(III) complexes. (C) 2000 Elsevier Science S.A. All rights reserved.