SYNTHESIS AND REACTIVITY OF CATIONIC (ETA-3-BUTADIENYL)PLATINUM COMPLEXES

(2-eta-1-Butadienyl)platinum(II) complexes can be obtained by reaction of [Pt(C2H4)(PPh3)2] with either chloroprene or 4-chloro-3-methylbuta-1,2-diene. Treatment of these complexes with AgPF6 provides direct access to the cationic eta-3-butadienyl complexes [Pt{eta-3-CH2:C(R):C:CH2}(PPh3)2][PF6] (R = H, Me), which surprisingly are attacked by the soft carbon nucleophile K-[CH(CO2Me)2] at the central carbon atom of the allylic moiety to form methyleneplatinacyclobutanes. These are unusual molecules that on thermolysis afford Pt(0) methylenecyclopropane complexes.