Zirconium complexes with alkynyl ligands

The tendency to form ate complexes observed for yttrium is also seen in the preparation of a novel zirconium alkynyl complex. Reaction of Zr(Por)Cl2 (Por = OEP or TPP) with either two or three equivalents of LiC=CR (R = Ph or SiMe ) gives the trisalkynyl complexes Zr(Por)(C=CR)3Li(TFIF). An X-ray crystal structure of Zr(OEP)(C=CPh)2Li(THF) shows that all three alkynyl ligands are on... 

The reaction of (OEP)ZrCl2 with 3equiv. of LiC=CPh produces the alkynyl (OEP)Zr(lv) porphyrin complex (OEP)Zr(7]1-C=CPh)3Li(THF) 242194 (Equation (18)). The molecular structure shows that three alkynyl ligands are coordinated to the Zr center in a piano-stool fashion and that the lithium cation is bound to the pocket formed by three alkynyl ligands. Treatment of complex 242 with anhydrous HC1 produces a C-C bond-coupled product H2C=C(Ph)=CPh and HC=CPh quantitatively. This example shows different reactivity of the zirconium porphyrin from that of analogous metallocene complexes. 

Zirconocene complexes 705 that contain an acetylide ligand bridging between a main group metal (aluminum) and a transition metal (zirconium) are obtained by treatment of dimethyl zirconocene with (alkynyl)dimethylaluminum, (Equation (43)).529 In this reaction, an ( 72-alkyne)zirconocene complex is presumably formed in situ, and it is then trapped by the excess (alkynyl)dimethylaluminum to yield the final product. The molecular structures of the complexes 705 (R = SiMe3, Cy) contain a dimetallabicyclic framework, and one of the bridgehead positions is a planar tetracoordinate carbon center. In these complexes, the -C=CR bridge between zirconium and aluminum can be described as being mainly of /x-(cr-acetylide) character. 

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