Preparation and 31 P NMR characterization of N-bonded complexes of platinum(II) with a phosphadithiatriazine: X-ray structure of trans -PtCl 2 (Pet 3 )(η 1 -N-Ph 2 PS 2 N 3 )

The reaction of Ph 2 PS 2 N 3 with [Pt 2 (μ-Cl) 2 (PEt 3 ) 4 ][BF 4 ] 2 or [PtCl 2 (PEt 3 )] 2 , in dichloromethane at 23° C produces the 1:1 adducts cis-[PtCl(PEt 3 ) 2 (Ph 2 PS 2 N 3 )][BF 4 ], 3, and trans-[PtCl 2 (PEt 3 )(Ph 2 PS 3 N 2 )], 4, respectively, in good yields. The 31 P NMR data for 3 and 4 indicate that (i) the platinum is attached to a nitrogen atom adjacent to phosphorus in both these adducts, (ii) the PEt 3 ligands in 3 are in mutually cis positions, and (iii) the PEt 3 ligand in 4 is trans to the heterocyclic nitrogen. These structural features were confirmed by an X-ray analysis of 4. Crystals of 4 are monoclinic, space group P2 1 /c, with a = 14.920(3) Å, b = 8.966(5) Å, c = 19.103(5) Å, β = 109.32(2)°, V = 2411.6(16) Å 3 , and Z = 4. The least-squares refinement with anisotropic thermal parameters for all non-hydrogen atoms converged at R = 0.050 and R w = 0.053. The Pt—N bond length is 2.122(15) Å and the coordinated nitrogen atom is lifted ca. 0.63(2) Å out of the plane containing the other heterocyclic ring atoms. The attachment of a platinum(II) centre to the PN 3 S 2 ring perturbs the S—N bond lengths significantly. The S—N distance involving the coordinated nitrogen is 1.672(16) Å, while the other S—N distances are 1.631(19), 1.555(19), and 1.562(19) Å, indicative of a localized sulfur diimide (-N=S=N-) structure. The UV–visible spectra of 3 and 4 in CH 2 Cl 2 exhibit absorption bands at 514 and 528 nm, respectively, but dissociation of these adducts to give the free ligand Ph 2 PS 2 N 3 occurs readily in dilute solution.