13C- und 15N-NMR-spektroskopische Untersuchungen einiger Pentacarbonylchrom-Aminophosphan-Komplexe/13C and 15N NMR Spectroscopic Study of Some Pentacarbonylchromium-Aminophosphane Complexes

Abstract

13C and 15N NMR data are reported for the free aminophosphanes ʹBu3-nP(NH2)n (n = 1 (1), 2 (2)), for the corresponding pentacarbonylchromium complexes (OC)5Cr-P(ʹBu)3-n(NH2)n (n = 1 (3), n = 2 (4), n = 3 (5)), and for other (OC)5Cr-aminophosphane complexes such as (OC)5Cr-P(NMe2)3, (6 ) and a binuclear complex (7) in which the sulfurdiimide derivative ʹBu(NH2)P-NSN-P(NH2)ʹBu serves as the phosphane ligand. Various techniques (e.g. INEPT and reverse two-dimensional (2D) 1H {15N}-experiments) have been used for recarding the 15N NMR spectra at natural abundance. In contrast to suggestions in the literature, the relationship between the 13C NMR parameters for the axial and equatorial CO groups and the σ-donor/π-acceptor properties of the phosphane ligand is not straightforward. The 15N resonances of the (OC)5Cr complexes 3, 4, 6 are shifted to higher frequencies with respect to those of the free ligands, and there is a regular decrease in 15N nuclear shielding in the series of 3, 4, 5. The |1J(31P15N)| values vary between 17 and 65 Hz, the smaller values being observed for the (OC)5Cr complexes. The lack of a regular change in the magnitude of 1J(31P15N) in the series 3, 4, 5 indicates that this parameter is influenced by the nature of both the Cr-P and the P-N bonds as a function of the number of amino groups.