Generation and Trapping of a 1,1‘-Diphosphazirconocene
摘要:
The reduction of [(eta(5)-C4Me4P)(2)ZrCl2] (1) by magnesium in THF affords a transient octamethyl-1,1'-diphosphazirconocene which can be trapped by CO, bis(trimethylsilyl)acetylene, and 2-butyne to give the corresponding dicarbonyl 2, zirconacyclopropene 3, and zirconacyclopentadiene 4; all of these products have been characterized by X-ray analyses. An assessment of the,pi-basicity of the eta(5)-C4Me4P ligand has been made by several methods: (a) a comparison of the IR carbonyl stretching frequencies of 2 and of other dicarbonylzirconocene complexes, (b) a correlation of the C-13 NMR and IR data in 3 and in similar zirconacyclopropenes, and (c) an electrochemical study on 1. All these experiments confirm that the eta(5)-C4Me4P ligand is a poorer pi-base than the Cp ligand.