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

The 195Pt NMR parameters of several phosphorus‐platinum(O) complexes [LnPt(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 T1 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 L2Pt complexes the relaxation rate varies with Bo2, and chemical shift anisotropy (CSA) is the dominant relaxation mechanism. In the L3Pt and L4Pt complexes spin‐rotation increasingly contributes to the relaxation. For the tirethylphosphine‐platinum complex (L3) the contribution of CSA is reduced by 45% at 7 T and 240 K, whereas the tetrahedral trimethylphosphine‐platinum (L4) and triethyl phosphite‐platinum (L4) complexes relax mainly by spin‐rotation even at 9.4 T.