Synthesis and characterization of amidate bridged dimeric and oligomeric platinum complexes having short platinum–platinum interactions

Abstract

A number of pivalamidate bridged dinuclear [Pt^II₂(RNH₂)₄(NHCOtBu)₂]²⁺, [Pt^III₂LL′ (RNH₂)₄(NHCOtBu)₂]ⁿ⁺ (2RNH₂ = 2NH₃, 1,2-ethylenediamine, 1,2-diaminocyclohexane; L, L′ = NO₃⁻, H₂O, or ketonate), trinuclear [{Pt^II(dap)(NHCOtBu)₂}₂Pd^III]³⁺ (dap = 1,2-diaminopropane), tetranuclear [{Pt^II₂(NH₃)₂(DACH)(NHCOtBu)₂}₂]⁴⁺ (DACH = 1,2-diaminocyclohexane), pentanuclear [{Pt₂(C₅H₇O)(NH₃)₂Cl₂(NHCOtBu)₂}₂PtCl₄], and hexanuclear [Pt₂(NH₃)₂(en)(NHCOtBu)₂Pt(NO₂)₄]₂ platinum complexes containing Pt(II)–Pt(II), Pt(II)–Pt(III), Pt(II)–Pd(III), and Pt(III)–Pt(III) interactions have been prepared and structurally characterized. The Pt–Pt interactions are characteristic of covalent, dative, or orbital symmetric Pt–Pt bonds. The dimeric Pt(III) complexes are able to activate C–H bonds of ketones to afford ketonate platinum(III) complexes. The Pt–Pt bonds are either doubly amidate-bridged or ligand unsupported. Their distances are 2.99–3.22 Å for Pt(II)–Pt(II), 2.59–2.72 Å for Pt(III)–Pt(III), 2.98 Å for Pt(II)–Pt(III), and 2.66 Å for Pt(II)–Pd(III) bonds depending on the oxidation states of the two metals and the ancillary ligands.