Synthesis of the Pivalamidate-Bridged Pentanuclear Platinum(II,III) Linear Complexes with Pt···Pt Interactions

Pentanuclear linear chain Pt(II,III) complexes {[Pt2(NH3)2X2((CH3)3CCONH)2(CH2COCH3)]2[PtX‘4]}·nCH3COCH3
(X = X‘ = Cl, n = 2 (1a), X = Cl, X‘ = Br, n = 1 (1b), X = Br, X‘ = Cl, n = 2 (1c), X = X‘ = Br, n = 1 (1d))
composed of a monomeric Pt(II) complex sandwiched by two amidate-bridged Pt dimers were synthesized from
the reaction of the acetonyl dinuclear Pt(III) complexes having equatorial halide ligands [Pt2(NH3)2X2((CH3)3CCONH)2(CH2COCH3)]X‘ ‘ (X = Cl (2a), Br (2b), X‘ ‘ = NO3-, CH3C6H4SO3-, BF4-, PF6-, ClO4-), with K2[PtX‘4] (X‘ = Cl,
Br). The X-ray structures of 1a−1d show that the complexes have metal−metal bonded linear Pt5 structures, and
the oxidation state of the metals is approximately Pt(III)−Pt(III)···Pt(II)···Pt(III)−Pt(III). The Pt···Pt interactions between
the dimer units and the monomer are due to the induced Pt(II)−Pt(IV) polarization of the Pt(III) dimeric unit caused
by the electron withdrawal of the equatorial halide ligands. The density functional theory calculation clearly shows
that the Pt···Pt interactions between the dimers and the monomer are made by the electron transfer from the
monomer to the dimers. The pentanuclear complexes have flexible Pt backbones with the Pt chain adopting either
arch or sigmoid structures depending on the crystal packing.