Palladium complexes cyclobutenyl

The cyclobutadienepalladium complexes (XXXVI) react with alcohols, usually in the presence of weak bases, to give cyclobutenylpalladium complexes (LXXXIV) isomeric with (XXXV) (see Section VI, F) these reactions are reversed on treatment of (LXXXIV) with hydrogen halides and constitute another preparation of the cyclobutadienepalladium complexes. A related reaction on (w-cyclopentadienyl)(7r-alkoxytetraphenyl-cyclobutenyl)palladium and -nickel complexes (XLIV) (64, 65) is also discussed in Section VI, F. The mechanism of this reaction is not established, but the initial step is probably protonation of the ether. 

Tetraphenylcyclobutadienepalladium and -nickel complexes and tetra-methylcyclobutadienenickel chloride react readily with nucleophilic reagents to give 7r-cyclobutenyl complexes 12, 30, 31, 65, 91), a reaction reminiscent of those described by Chatt et al. for diene-palladium and diene-platinum halide complexes (Section VI, F). Non-halogen-containing cyclobutadiene complexes, however, appear inert under similar conditions so that this reaction is very dependent on the other ligands present. Some similarity between cyclobutadiene-metal and diene-metal complexes appears to exist but how far the parallel can be drawn remains to be seen. The reactions are fully discussed in Section VI. 

Analogous reversible reactions occur with tetraphenylcyclobutadiene-palladium halides (12,69, 70,91) to form cyclobutenyl complexes isomeric... 

Maiths and co-workers (1620,1621) reported the synthesis of a number of novel palladium(II) organometallic complexes formed from ring-opening reactions of pentaaryl cyclobutenyl complexes (Fig. 212). Thus, addition of... 

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