PD(C6F5)BR, A CONVENIENT PRECURSOR FOR STUDYING THE ENDO ATTACK OF NUCLEOPHILES ON OLEFINS - X-RAY STRUCTURE OF BIS(MU-BROMO)BIS(4-(PENTAFLUOROPHENYL)-1-3-ETA-3-CYCLOHEXENYL)DIPALLADIUM(II)

Acyclic and cyclic diolefins insert into Pd-C6F6 bonds of isolable “Pd(C6F5)Br” synthons to give η3-allyl complexes. The reactions are regiospecific; the C6F5 in the product is always attached to one external carbon of the diene system, and the allyl moiety is formed at the position of the unattacked double bond. Furthermore, the reactions are stereospecific; the X-ray determination of the title complex (7a) shows that the C6F5 group (which was coordinated to Pd in the precursor) and the Pd atom are on the same face of the cyclohexenyl ring. 7a crystallizes in the triclinic space group P1 with a = 15.4376 (22) Å, b = 7.3616 (7) Å, c = 5.7056 (5) Å, α = 107.77 (1)°, β = 82.08 (1)°, and γ = 89.01 (2)° (Z = 1). Least-squares refinement leads to final R of 0.076 for 2064 independent reflections. Styrene reacts with these synthons to give trans-PhCH═CH(C6F5), and this reaction models, as an isolated reaction, the proposed second step in the Heck arylation reactions. © 1990, American Chemical Society. All rights reserved.