Chemistry of metallacyclobutanones. Part 3. Reactions of heptane-2,4,6-trione and 1,5-diphenylpentane-1,3,5-trione with some carbonate complexes of platinum(II); X-ray crystal structures of [Pt{CH(COMe)COCH(COMe)}(PPh3)2] and [Pt{OC(CHCOPh)CHC(Ph)O}(PPh3)2]

Abstract

Heptane-2,4,6-trione reacts with the carbonate complexes [Pt(CO₃)L₂] in warm ethanol to afford high yields of the piatinacyclobutan-3-one complexes [P[graphic omitted]HR)L₂](R = COMe, L = PPh₃ or AsPh₃). A single-crystal X-ray diffraction study has been carried out on the complex [[graphic omitted]H(COMe)}(PPh₃)₂]. The molecular structure can be considered to be based upon a highly puckered platinacyclobutan-3-one ring complex [fold angle 48.0(4)°] with a weak transannular Pt–C bond of 2.486(6)Å, the allylic structure [Pt{η³–CH(COMe)COCH(COMe)}(PPh₃)₂] making a significant contribution to the bonding. N.m.r. data (¹H, ¹³C-{¹H}) are reported and variable-temperature ¹H n.m.r. data for the complexes [P[graphic omitted]H(COMe)}L₂](L = PPh₃ or AsPh₃) are interpreted in terms of inversion of the platinacyclobutan-3-one ring through a planar transition state. In contrast, 1,5-diphenylpentane-1,3,5-trione reacts with [Pt(CO₃)(PPh₃)₂] in warm ethanol to afford the dienediolate complex [[graphic omitted]}(PPh₃)₂] which was characterised by X-ray crystallography.