Insertion reaction of dimethylacetylenedicarboxylate with the head-to-tail isomer of Pt 2I 2(μ-Ppy 3) 2; Ppy 3=tris(2-pyridyl)phosphine

Abstract

The head-to-tail (HT) isomer of Pt 2I 2(μ-Ppy 3) 2 ( 3), where py=2-pyridyl, is made by reaction of NaI with the chloro analogue ( 2), which it itself synthesized via a conproportionation reaction of a Pt(O) complex and cis-PtCl 2(μ-Ppy 3) 2 ( 1). Complex 1 is formed by reacting appropriate Pt(II) precursors with Ppy 3. Dimethyl acetylenedicarboxylate (DMAD) inserts into the PtPt bond of 3 to give the A- frame species HT-Pt 2I 2(μ-Ppy 3) 2(μ-DMAD) ( 4); the reaction is kinetically first-order in both [ 3] and [DMAD], and the activation parameters (Δ H ≠=38 kJ mol −1, (Δ S ≠=−138 J mol −1 K −1) are consistent with a concerted process involving a four-centre transition state. Complexes 1–4 are characterized by elemental analyses and 31p{ 1H} and 195Pt{ 1H} NMR spectroscopy.