Platinabenzenes: Synthesis, Properties, and Reactivity Studies of a Rare Class of Metalla-aromatics

Lithium−halogen exchange of (Z)-1,2-diphenyl-3-(2-iodoethenyl)cyclopropene (1) and subsequent addition to (η4-1,5-cod)PtCl2 yields the platinabenzene (η5-C5H3Ph2)[PtC5H3Ph2] (7), in which the metallacyclic ring and C5H3Ph2 (Cp′) unit are both derived from the cyclopropene skeleton. Starting instead with (η5-C5Me5)Pt(CO)I, treatment with three nucleophilic (Z)-3-(2-lithiovinyl)cyclopropenes provides platinabenzenes (η5-C5Me5)[PtC5H3PhR] (R = Ph (8), t-Bu (9), Me (10)) in low to modest yield. All platinabenzenes have been fully characterized by NMR spectroscopy and X-ray crystallography. Intermediate σ-vinyl complexes (η5-C5Me5)Pt(σ-C5H3PhR) (R = Ph (14), t-Bu (15)) are also isolated from the reaction mixtures and convert cleanly to the corresponding platinabenzenes in near quantitative yield. Reactivity studies of (η5-C5Me5)[PtC5H3Ph2] with a variety of reagents/conditions are also reported.