Synthesis and structure of mono- and di-nuclear complexes of ortho-palladated derived from phosphorus ylides

The phosphorus ylides Ph3PCHC(O)C6H4R (R = 4-Me 1a, 4-Br 1b) react with PdCl2 in equimolar ratios to give the C,C-orthopalladated [Pd{CHP(C6H4)Ph2CO-C6H4–R)}(μ-Cl)]2 (R = 4-Me 2a, 4-Br 2b) which react with NaClO4/dppe, NaClO4/dppm, py and PPh3 to give the mononuclear derivatives [Pd{CH{P(C6H4)Ph2}COC6H4-R}(dppe-P,P′)[(ClO4) (R = 4-Me 3a, 4-Br 3b), [Pd{CH{P(C6H4)Ph2}COC6H4-R}(dppm-P,P′)[(ClO4 ( (R = 4-Me 4a, 4-Br 4b), [Pd{CH{P(C6H4)Ph2}COC6H4-R}Cl(L)] (L = py, R = 4-Me 5a, 4-Br 5b, L = PPh3, R = 4-Me 6a, 4-Br 6b). The C, C-metalated chelate are demonstrated by an X-ray diffraction study of 3a and 4a. Characterization of the obtained compounds was also performed by elemental analysis, IR, 1H, 31P, and 13C NMR.

Reaction of two the C,C-orthopalladated complexes [Pd{CHP(C6H4)Ph2CO–C6H4–R)}(μ-Cl)]2 (R = 4-Me, 4-Br) with NaClO4/dppe, NaClO4/dppm, Py and PPh3 is reported. X-ray crystal structures analysis of [Pd{CH{P(C6H4)Ph2}COC6H4-CH3}(dppe-P,P′)[(ClO4) (3a) and [Pd{CH{P(C6H4)Ph2}COC6H4-CH3}(dppm-P,P′)[(ClO4( (4a) shows that the C, C-metalated chelate has occurred. Characterization of the obtained compounds was also performed by elemental analysis, IR, 1H, 31P, and 13C NMR.Figure optionsDownload as PowerPoint slideHighlights
► The palladation of α-keto stabilized phosphoylides occurs regioselectively at the PPh3 group.
► This orthopalladation gives five-membered endo metallacycles of high stability.
► The dppe group behaves as an P,P-chelate ligand and is bonded to the Pd giving a five membered ring.
► The dppm group behaves as an P,P-chelate ligand and is bonded to the Pd giving a four membered ring.
► The reaction of the dinuclear complexes with Py lead to complexes with two isomers (cis and trans).