PLATINUM(II) COMPLEXES OF N,N'-DI-(N)BUTYLDITHIOOXAMIDE SHOWING A PECULIAR -H...CL- INTERACTION - THE CRYSTAL AND MOLECULAR-STRUCTURE OF BIS-DI-(N)BUTYLDITHIOOXAMIDATO-PLATINUM(II)(N)

N,N'-di-butyldithiooxamide, (n)bu2-DTO, reacts in chloroform with neut ral complexes of the type cis-PtL2Cl2. When L=bz2S or 1/2COD the tight contact ion pair {Pt(H2-(n)bu2-DTO)22+,(Cl-)2} (1) is obtained for an y metal to ligand ratio. When L is Me2SO the ion pair {(Me2SO)ClPt(H2- (n)bu2-DTO+,(Cl-)} (2) separates in the solid state on adding the liga nd to platinum in a 1:1 ratio. This monochelate complex, however, is u nstable in chloroformic solution where a symmetrization equilibrium wi th the corresponding bis-chelate ion pair 1 and the dichloroplatinum s tarting material can be found. Compound 1 by reaction with pyridine, d ipyridine, phenanthroline or similar nitrogen Lewis bases loses one or both HCl molecules so giving {Pt(H-(n)bu2-DTO)(H2-(n)bu2-DTO)+,(CL-)} (3) or [Pt(H-(n)bu2-DTO)2] (4), depending on the base concentration. Dissolution of 1 in a basic solvent (DMF, alcohols) leads to the forma tion of the neutral species 4, which is also formed when a chloroformi c solution of 1 undergoes a double phase reaction with the -OH group o f H-OH, =Al-OH or =Si-OH. Compound 4 crystallizes in the monoclinic sp ace group P2(1)/c, with a=10.572(2), b=10.748(1), c=12.165(2) angstrom , beta=93.37(2)degrees, V=1379.9(4) angstrom3, Z=2 and D(calc)=1.58 g cm-3 ; the structure was refined to R=0.033 and R(w)=0.038. The [Pt(H- (n)bu2-DTO)2] complex has imposed square-planar geometry about the Pt atom, two thioamide S atoms of the (n)bu2-DTO molecule acting as a che lating ligand. The two crystallographically independent values for the Pt-S bond distance are: Pt-S(1)=2.297(3) angstrom and Pt-S(2)=2.284(2 ) angstrom, the bond angles are very close to 90-degrees. The deproton ated complex [Pt(H-(n)bu2-DTO)2] (4) restores the ion pair by a double phase reaction with aqueous HCl, while none of the oxoacids is able t o give {Pt(H2-nbu2-DTO)22+,(Ox-)2} (Ox-=oxoanion). As a consequence, t he +N-H...Cl-hydrogen interaction in {Pt(H2-(n)bu2-DTO)22+,(Cl-)2} is thought to be crucial in stabilizing the tight ion pair.