31P NMR and DFT studies on square-planar bis(diphenylphosphinoethyl)phenylphosphine (triphos) complexes of Pt(II) with pyridines and anilines

Cationic complexes of the type [Pt(L)(triphos)](ClO4)(2). where L is a 4-substituted pyridine {L=4-R-py=4-cyanopyridine (4-CN-py), isonicotinic acid (4-COOH-py), methylisonicotinate (4-COOMe-py). 4-acetylpyridine (4-MeCO-py), pyridine (4-H-py), 4-methylpyridine (4-Me-py), 4-aminopyridine (4-NH2-py)} or a 4-substituted aniline {L = 4-R-an = 4-nitroaniline (4-NO2-an), 4-cyanoaniline (4-CN-an), 4-chloroaniline (4-Cl-an), aniline (4-H-an), 4-methylaniline (4-Me-an), 4-methoxvanifine (4-MeO-an)}, have been prepared from cis/trans-PtCl2{SMe2)(2). The cis and trans (1)J(Pt) (P) coupling constants measured in CD3NO2 were found to be dependent upon the pK(a) of L. For the series of the para-substituted pyridines 4-R-py the linear correlations (1)J(Pt-P1) = 2918 - 16.9 pK(a) and V-1(Pt-P2) = 2371 + 5.8 pK(a) (PI = phosphorus nucleus trans to N, P-2 = phosphorus nuclei cis to N) were found. The complexes with L = para-substituted anilines 4-R-an show a different behaviour. The results are discussed on the basis of DFT calculations. (c) 2005 Elsevier Ltd. All rights reserved.