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Chemistry of Metallacyclobutanones. Part 2. Synthesis and Ring Inversion of some Highly Puckered Metallacyclobutan-3-one (Slipped Oxodimethylenemethane) Complexes of Palladium; Crystal Structures of 2,4-Bis(methoxycarbonyl)-1,1-bis(triphenylphosphine)palladacyclobutan-3-one, 2,4-Bis(m...

DOI: 10.1039/DT9850000259

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 259 - 268 (1985)

Update date:2022-08-03

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Authors:

Kemmitt, Raymond D. W.Kemmitt, Raymond D. W.

McKenna, PeterMcKenna, Peter

Russel, David R.Russel, David R.

Sherry, Lesley J. S.Sherry, Lesley J. S.

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Article abstract of DOI:10.1039/DT9850000259

The reactions of the zerovalent palladium complex *CHCl3 (dba=dibenzylideneacetone, PhCH=CH-C(O)-CH=CHPh), in the presence of a donor ligand L and dioxygen, with esters of 3-oxopentanedioic acid (RCH2COCH2R) in diethyl ether, afford, in high yield, the palladacyclobutan-3-one compounds n, L2=bipy>.The compounds (R=CO2Me or CO2Et, L=PPh3 or AsPh3) are also formed upon treatment of benzene solutions of with RCH2COCH2R in the presence of air.Treatment of the ketone MeO2CCH2COCH2CO2Me with either in benzene or in ethanol also affords .Spectroscopic data (i.r. and n.m.r.) for the new compounds are reported, and discussed in relation to their structures, which were firmly established for by single-crystal X-ray diffraction studies.Crystals of (3a) are triclinic, space group P1/, Z=2, in a unit cell with lattice parameters a=11.995(5), b=17.72(1), c=10.30(1) Angstroem, α=94.7(1), β=110.8(1), and γ=102.84(2) deg.The structure was refined to R 0.055 (R' 0.060) for 5093 reflections having 7<=2Θ<=54 deg (Mo-KαX-radiation) collected at room temperature.Crystals of (3e) are triclinic, space group P1/, Z=2, in a unit cell with lattice parameters a=12.219(6), b=17.56(1), c=10.44(1) Angstroem, α=93.3(1), β=110.8(1), and γ=103.56(2) deg.The structure was refined to R 0.043 (R' 0.046) for 6025 reflections having 7<=2Θ<=54 deg collected at room temperature.Crystals of (3f) are monoclinic, space group P21/c, Z=4, in a unit cell with lattice parameters a=8.43(1), b=14.594(6), c=14.170(6) Angstroem, and β=92.1(1) deg.The structure was refined to R 0.043 (R' 0.032) for 4000 reflections having 7<=2Θ<=60 deg collected at room temperature.The three molecules contain a highly puckered palladacyclobutan-3-one ring with a weak transannular Pd-C bond .The molecules can be alternatively formulated with slipped η3-oxodimethylenemethane ligands.Variable-temperature 1H n.m.r. data for the compounds (R=CO2Me, L=PPh3, PMePh2, PMe2Ph, PEt3, or AsPh3; L2=bipy) are interpreted in terms of inversion of the palladacyclobutan-3-one ring through a planar transition state.

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