Heavy metal spin‐ ½ nuclei. Platinum‐195 relaxation times in phosphorus‐platinum(o) compounds and their dependence on the geometry of the complex

Abstract

Abstract The 195 Pt NMR parameters of several phosphorus‐platinum(O) complexes [L n Pt(O), L = phosphine or phospite, n = 2, 3, 4] have been investigated to illustrate the particular NMR properties of a spin‐1/2 heavy metal nucleus, and for elucidation of their dependence on the geometry of the complexes. In these compounds the T 1 values vary as a function of the coordination number, n, over several orders of magnitude and, therefore, can be used as structure‐dependent parameters. In L 2 Pt complexes the relaxation rate varies with B o 2 , and chemical shift anisotropy (CSA) is the dominant relaxation mechanism. In the L 3 Pt and L 4 Pt complexes spin‐rotation increasingly contributes to the relaxation. For the tirethylphosphine‐platinum complex (L 3 ) the contribution of CSA is reduced by 45% at 7 T and 240 K, whereas the tetrahedral trimethylphosphine‐platinum (L 4 ) and triethyl phosphite‐platinum (L 4 ) complexes relax mainly by spin‐rotation even at 9.4 T.