Synthesis and Structure of the Hafnium Alkylidene Complex [P2Cp]HfCHPh(Cl) ([P2Cp] = (η5-C5H3-1,3-(SiMe2CH2PPri 2)2))

• Published in: Organometallics 2001-04, Vol.20 (8), p.1608-1613
• Main Authors: Fryzuk, Michael D, Duval, Paul B, Patrick, Brian O, Rettig, Steven J
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om000760i

The synthesis, structural characterization, and solution behavior of hafnium complexes stabilized by the potentially tridentate ancillary ligand [P2Cp] ([P2Cp] = (η5-C5H3-1,3-(SiMe2CH2PPri 2)2)) are described. The reaction of [P2Cp]Li with HfCl4(THT)2 produces the hafnium trichloride complex [P2Cp]HfCl3 (1), the structure of which was determined by X-ray crystallography. Trichloride 1 is isostructural with the analogous zirconium complex [P2Cp]ZrCl3 (2) in the solid state, but in solution 1 exists as an equilibrium mixture of two isomers that interconvert by fluxional phosphine coordination. Treatment of 1 with 2 equiv of KCH2Ph, followed by thermolysis, yields the first structurally characterized hafnium alkylidene complex, [P2Cp]HfCHPh(Cl) (3). A crystal structure determination obtained for 3 shows this complex to be isostructural with the zirconium analogue [P2Cp]ZrCHR(Cl) (4). The primary difference between the Hf systems presented here and the previously studied Zr analogues is that metal−ligand bonding is stronger in the former, which accounts for shorter bond distances, a greater degree of chemically inertness, and the divergent solution behaviors observed for the trichloride derivatives 1 and 2.