Synthesis and structure of 1,3-dienolate (CH2C(O)CH=CH2) complex of dipalladium(I) moiety: contribution of pi-olefin co-ordination of enolate to transition metal

1,3-Dienolate dipalladium(I) complex [{mu-CH2C(O)CH=CH2}Pd-2(PPh3)(2)(mu-Cl )] (2) is prepared and characterized. Complex 2 is easily protonated to yie ld 2-hydroxy-1,3-butadiene dipalladium(I) complex [{(mu-eta(2):eta(2)-CH2=C (OH)CH=CH2}Pd-2(PPh3)(2)(mu-Cl)][BF4] (3). On the basis of the comparative analyses on IR and NMR spectra and X-ray structure analysis, the co-ordinat ion mode of 1,3-dienolate on Pd-Pd is revealed to involve the resonance bet ween C-bound and pi-olefin-bound enolate structures. (C) 1999 Elsevier Scie nce S.A. All rights reserved.