Quantification of cis and trans influences in [PtX(PPh3)3]+ complexes. A 31P NMR study

In [PtX(PPh3)3]+ complexes (X = F, Cl, Br, I, AcO, NO3, NO2, H, Me) the mutual cis and trans influences of the PPh3 groups can be considered constants in the first place, therefore the one bond Pt-P coupling constants of P(cis) and P(trans) reflect the cis and trans influences of X. The compounds [PtBr(PPh3)3](BF4) (2), [PtI(PPh3)3](BF4) (3), [Pt(AcO)(PPh3)3](BF4) (4), [Pt(NO3)(PPh3)3](BF4) (5), and the two isomers [Pt(NO2-O)(PPh3)3](BF4) (6a) and [Pt(NO2-N)(PPh3)3](BF4) (6b) have been newly synthesised and the crystal structures of 2 and 4×CH2Cl2×0.25C3H6O have been determined. From the 1JPtP values of all compounds we have deduced the series: I > Br > Cl > NO3 > ONO > F > AcO > NO2 > H > Me (cis influence) and Me > H > NO2 > AcO > I > ONO > Br > Cl > F > NO3 (trans influence). These sequences are like those obtained for the (neutral) cis- and trans-[PtClX(PPh3)2] derivatives, showing that there is no dependence on the charge of the complexes. On the contrary, the weights of both influences, relative to those of X = Cl, were found to depend on the charge and nature of the complex.