Preparation and 31P NMR characterization of N-bonded complexes of platinum(II) with a phosphadithiatriazine: X-ray structure of trans-PtCl2(Pet3)(η1-N-Ph2PS2N3)

Abstract

The reaction of Ph2PS2N3 with [Pt2(μ-Cl)2(PEt3)4][BF4]2 or [PtCl2(PEt3)]2, in dichloromethane at 23° C produces the 1:1 adducts cis-[PtCl(PEt3)2(Ph2PS2N3)][BF4], 3, and trans-[PtCl2(PEt3)(Ph2PS3N2)], 4, respectively, in good yields. The 31P 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 PEt3 ligands in 3 are in mutually cis positions, and (iii) the PEt3 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 P21/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) Å3, and Z = 4. The least-squares refinement with anisotropic thermal parameters for all non-hydrogen atoms converged at R = 0.050 and Rw = 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 PN3S2 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 CH2Cl2 exhibit absorption bands at 514 and 528 nm, respectively, but dissociation of these adducts to give the free ligand Ph2PS2N3 occurs readily in dilute solution.