Five-coordinate organo-zirconocene-ate complexes: Synthesis and reactivity

A variety of stable five-coordinate organo-zirconocene-ate complexes, 2-4, 9, 12a,b, 16, and 18, have been prepared and structurally characterized. The reaction process is based on both (i) the nucleophilic attack of tertiary phosphines on acetylenic reagents and (ii) the ability for 16-electron d(0)-zirconocene(IV) complexes to coordinate two electron donor ligands. We have shown that the nature of the heteroelement directly bonded to the triple bond of the terminal acetylenic system directs the nucleophilic attack of the phosphine; in all cases only one regioisomer is observed. Surprisingly, the nucleophilic attack of the phosphine in la occurs on propargyl derivatives 19-21 to give the corresponding zwitterionic zirconate complexes 22-24. The reactivity of 12a with HCl and MeI has been tested.