REACTIONS OF 2-DIAMINOETHANE-N,N,N'N'-TETRA(N-METHYLACETAMIDE), L, WITH POTASSIUM TETRACHLOROPLATINATE(II) - CRYSTAL AND MOLECULAR-STRUCTURES OF PT(LH(-2))CL-2-CENTER-DOT-2H(2)O, A NOVEL PLATINUM(IV) COMPLEX CONTAINING DEPROTONATED AMIDE LIGANDS, AND OF (2H(-L)[PTCL4]())

Reaction of -diaminoethane-N,N,N',N'-tetra(N-methylacetamide), L, with potassium tetrachloroplatinate(II) in aqueous solution afforded the c rystalline salt (2H(+)-L)[PtCl4] and the neutral platinum(IV) complex cis-Pt(LH(-2))Cl-2 . 2H(2)O. The crystal and molecular structure of th e latter shows that the chloride ligands are cis, Pt-Cl=2.308(2) Angst rom, and that LH(-2) is present as a tetradentate ligand coordinated t hrough its two amino nitrogen atoms, Pt-N=2.097(6) Angstrom, and two d eprotonated amide nitrogens, Pt-N=2.032(4) Angstrom which are trans to each other. This structure is the first of a platinum(IV) complex con taining deprotonated amide ligands and may serve as a model for platin um(N)-peptide/protein: interactions. The fact that this complex is for med without any added oxidant other than air suggests that deprotonate d amide groups facilitate the oxidation of platinum(II) to platinum(IV ). The C-N and C=O bond distances in the coordinated, deprotonated ami de groups are almost identical to those of the uncoordinated amide gro ups indicative of similar rr electron delocalisation in the NCO groups in both cases. This is in contrast to the situation in a recently rep orted platinum(II)-amidate complex in which there is considerably grea ter pi electron delocalisation than in the free amide. The crystal str ucture of (2H(+)-L)[PtCl4] is also reported, av. Pt-Cl=2.292 Angstrom. Crystal data: cis-Pt(LH(-2))Cl-2 . H2O, monoclinic, space group P2/n, a=11.764(4), b=7.840(1), c=11.829(4) Angstrom, beta=104.09(2)degrees, Z=2; (2H(+)-L)[PtChl(4)], triclinic, space group P1, a=9.035(1), b=9. 316(1), c=7.308(2) Angstrom, alpha=100.88(1), beta=106.52(1), gamma=99 .96(1)degrees, Z=1.