SYNTHESIS AND STRUCTURE DETERMINATION OF RH-DIENE COMPLEXES WITH THE HYDRIDOTRIS(3,5-DIISOPROPYLPYRAZOLYL)BORATE LIGAND, TP(IPR)RH(DIENE) (DIENE = COD, NBD) - DEPENDENCE OF THE NU(B-H) VALUES ON THE HAPTICITY OF THE TP(IPR) LIGAND (KAPPA(2) VS KAPPA(3))(1)

Rhodium-diene complexes with the Tp(iPr) ligand, Tp(iPr)Rh(diene) (Tp( iPr) = hydridotris(3,5-diisopropylpyrazolyl)borate; diene = 1,5-cycloo ctadiene (cod) (1), norbornadiene (nbd) (2)), are prepared by treatmen t of [Rh(mu-Cl)(diene)](2) with KTp(iPr) or TlTp(iPr), The structure o f 1, characterized by X-ray crystallography, contains the kappa(2)-coo rdinated Tp(iPr) ligand, and its central Rh atom adopts a square-plana r geometry, whereas the unit cell of 2 contains two independent molecu les: a square-planar structure with a kappa(2)-coordinated Tp(iPr) lig and similar to 1 and a trigonal-bipyramidal one with a kappa(3)-coordi nated Tp(iPr) ligand, Although H-1 and C-13 NMR spectroscopy does not provide any information concerning the coordination geometry due to th e interconversion between the square-planar and trigonal-bipyramidal s tructures, which occurs at a rate much faster than the NMR time scale, IR analysis reveals that the bands observed around 2470 and 2540 cm(- 1) are assigned to the B-H stretching vibrations of the square-planar and trigonal-bipyramidal structures, respectively, Thus, the nu(B-H) v alue can be used as an indicator of the hapticity of a Tp(iPr) ligand (kappa(2) (similar to 2470 cm(-1)) us kappa(3)(>2530 cm(-1))) as compa red with related Tp(iPr)ML(n)-type complexes.