Triangular Trinuclear Cluster Complexes of Platinum (II)

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The objective of the present study is synthesis, strucuture, reactivity, and electronic structure of the titled compound whose cluster core structure has been found for the first time by the author's group. Main reults are as follows.1.Establishment of the synthetic method. Desired compounds are derived from tetranuclear platinum (II) cluster complex, [Pt_4 (OAc) _8]. Triangular platinum (II) cluster complexes can be prepared via following two routes, although in-plane ligands are limited to bidentate chelate ligand with nitrogen donors such as glyoxime and diamines.Method A (based on cluster core transformation from the square-planar type). When [Pt_4 (OAc) _8] is allowed to react with glyoximes or diamins in which the surroundings of donor atoms are sterically crowded, desired compounds with the triangular cluster core are prepared through core structure transformation.Method B (based on in-plane ligand substitution of complexes made by Method A). When ethylenediamine or N,N'-dimethy … More lethylendiamine are used as in-plane ligand, Method A is not applicable, but desired compounds are obtained by in-plane ligand substituion of, e.g., glyoxime complexes prepared by Method A.2.Structural studies by means of ^<l95>Pt-, ^<l3>C-, ^1H-NMR and X-ray analyzes. In all the compounds, the cluster core structure was an isosceles triangle. There exist direct Pt-Pt bonds in the cluster core. Magnitude of neclear spin-spin coupling constant J_<Pt-Pt> was 7500-8000 Hz.3.Electronic Structure of the triangular cluster core. EHMO calculation shows that the cluster core of this type is electronically stable, and that platinum atoms at the apices of the triangle are bound by Pt-Pt single bond.4.Substitution lability of the ligand which is in the cluster plane. We had expected labilization by the trans effect of the Pt-Pt bond as in [Pt_4 (OAc) _8] with the square-planar core. Results shows, however, no marked labilization. This is due to the following reasons. All the compounds prepared in this study have nitrogen donor ligands at the in plane sites and Pt-N bond is much stringer than Pt-O bond. Further, glyoxime complexes have intra-molecular hydrogen bonds in the cluster plane. Less