Multinuclear Solid-State NMR and DFT Studies on PhosphanidoBridged Diplatinum Complexes

Multinudear (P-31, Pt-195, F-19) solid-state NMR experiments on (nBu(4)N)(2)[C6F5)(2)Pt(mu-PPh2)(2)Pt(C6F5)(2)] (1), [(C6F5)(2)Pt(mu-PPh2)(2)Pt(C6F5)(2)] (Pt-Pt) (2), and cis-Pt(C6F5)(2)(PHPh2)(2) (3) were carried out under cross-polarization/magic-angle-spinning conditions or with the crosspolarization/Carr Purcell Meiboom Gill pulse sequence. Analysis of the principal components of the P-31 and Pt-195 chemical shift (CS) tensors of 1 and 2 reveals that the variations observed comparing the isotropic chemical shifts of 1 and 2, commonly referred to as "ring effect", are mainly due to changes in the principal components oriented along the direction perpendicular to the Pt2P2 plane. DFT calculations of P-31 and Pt-195 CS tensors confirmed the tensor orientation proposed from experimental data and symmetry arguments and revealed that the different values of the isotropic shieldings stem from differences in the paramagnetic and spin-orbit contributions.