INSERTION REACTION OF DIMETHYLACETYLENEDICARBOXYLATE WITH THE HEAD-TO-TAIL ISOMER OF PT2I2(MU-PPY3)2 PPY3=TRIS(2-PYRIDYL)PHOSPHINE

The head-to-tail (HT) isomer of Pt2I2(mu-Ppy3)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(0) complex and cis-PtCl2(mu-PPY3)2 (1). Complex 1 is formed by reacting appropriate Pt(II) precursors with Ppy3. Dimethylacetylenedicarboxylate (DMAD) inserts into the Pt-Pt bond of 3 to give the A-frame species HT-Pt2I2(mu-PpY3)2(mu-DMAD) (4); the reaction is kinetically first-order in both [3] and [DMAD], and the activation parameters (DELTAH(not-equal) = 38 kJ mol-1, DELTAS(not-equal) = -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 (P{H})P-31-H-1 and (Pt{H})-Pt-195-H-1 NMR spectroscopy.