195Pt, 119Sn and 31P NMR studies of alkyl, aryl and acyl trichlorostannate complexes of platinum(II). The crystal structure of trans-[Pt(SnCl 3)(COC 6H 5)(PEt 3) 2

Abstract

195Pt, 119Sn and 31P NMR characteristics of the complexes trans-[Pt(SnCl 3)(carbon ligand)(PEt 3) 2] ( 1a- 1e) are reported, (carbon ligand = CH 3 ( 1a), CH 2Ph ( 1b), COPh ( 1c), C 6Cl 5 ( 1d), C 6Cl 4Y ( e); Y = meta- and para-NO 2, CF 3, Br, H, CH 3, OCH 3, or Pt(SnCl 3)(PEt 3) 2. The values of 1 J( 195Pt, 119Sn) vary from 2376 to 11895 Hz with the COPh ligand having the smallest and the C 6Cl 5 ligand the largest value, making a total range for this coupling constant, when the dimer syn- trans-[PtCl(SnCl 3)(PEt 3)] 2 is included, of ca. 33000 Hz. In the meta- and para-substituted phenyl complexes 1 J( 195Pt, 119Sn) (a) is greater for electron-withdrawing substituents, (b) varies more for the meta-substituted derivatives (5634 to 7906 Hz) than for the para analogues (6088 to 7644 Hz) and (c) has the lowest values when the Pt(SnCl 3)(PEt 3) 2 group is the meta- or para-substituent. The direction of the change in 1 J( 195Pt, 119Sn) is opposite to that found for 1 J( 195Pt, 119P). For the aryl complexes linear correlations are observed between δ( 119Sn), 1 J( 195Pt, 119Sn), 1 J( 195Pt, 31P), 1 J( 119Sn, 31P) and the Hammett substituent constant σ n . δ( 119Sn) and 1 J( 195Pt, 119Sn) are related linearly to v(Pt-H) in the complexes trans-[PtH(C 6H 4Y)(PEt 3) 2]; δ( 119Sn) and δ( 1H) (hydride) are also linearly related. Based on 1 J( 195Pt, 119Sn), the acyl ligand is suggested to have a very large NMR trans influence. The differences in the NMR parameters for ( 1a-e) are rationalized in terms of differing σ- and π-bonding abilities of the carbon ligands. The structure of 1c has been determined by crystallographic methods. The complex has a slightly distorted square planar geometry with trans-PEt 3 ligands. Relevant bond lengths (Å) and bond angles (°) are: PtSn, 2.634(1), PtP, 2.324(4) and 2.329(4), PtC, 2.05(1); PPtP, 170.7(6), SnPtC, 173.0(3), SnPtP, 92.1(1), 91.7(1), PPtC, 88.8(4) and 88.3(4). The PtSn bond separation is the longest yet observed for square-planar platinum trichlorostannate complexes, and would be consistent with a large crystallographic trans influence of the benzoyl ligand. The PtSn bond separation is shown to correlate with 1 J( 195Pt, 119Sn).