Solid-state NMR spectroscopy of paramagnetic metallocenes.

Abstract The paramagnetic metallocenes and decamethylmetallocenes (C 5 H 5 ) 2 M and (C 5 Me 5 ) 2 M with M =V ( S = 3 2 ), Mn ( S = 5 2 or 1 2 ), Co ( S = 1 2 ), and Ni ( S =1) were studied by 1 H and 13 C solid-state MAS NMR spectroscopy. Near room temperature spinning sideband manifolds cover ranges of up to 1100 and 3500 ppm, and isotropic signal shifts appear between −260 and 300 ppm and between −600 and 1640 ppm for 1 H and 13 C NMR spectra, respectively. The isotropic paramagnetic signal shifts, which are related to the spin densities in the s orbital of ligand atoms, were discussed. A Herzfeld–Berger spinning sideband analysis of the ring carbon signals yielded the principal values of the paramagnetic shift tensors, and for metallocenes with a small g -factor anisotropy the electron spin density in the ligand π system was determined from the chemical shift anisotropy. The unusual features of the 1 H and 13 C solid-state NMR spectra of manganocene were related to its chain structure while temperature-dependent 1 H MAS NMR studies reflected antiferromagnetic interaction between the spin centers.