Hafnium(IV) complexes with Schiff bases

Hafnium(IV) complexes have been prepared by the reactions of hafnium(IV) isopropoxide isopropanol with Schiff bases [bis(salicylaldehyde)hydrazine] (Sal-AH2), (bis(o-hydroxyacetophenone)hydrazine] (Acp-AH2), [bis(resacetophenone)hydrazine] (Res-AH2), [bis(salicylaldehyde)ethylenediimine) (SaleneH2), [bis(o-hydroxyacetophenone)ethylenediimine] (AcpeneH2) and [bis(salicylaldehyde)o-phenylenediimine] (SalpheneH2) (derived from salicylaldehyde,o-hydroxyacetophenone, resacetophenone and diamines) in appropriate molar ratios using benzene as solvent. The complexes [Hf(OPr-i)2(SB)] and [Hf(SB)2] (where SB2− represents the dianion of the Schiff base) are reported. The complexes of Sal-A, Acp-A and Res-A are 5-and 6-coordinate while those of salene, acpene and salphene are 6-and 8-coordinate. The Schiff bases draw on Sal-A, Acp-A and Res-A are tridentate and salene, acpene and salphene are tetradentate. The mode of bonding through nitrogen and oxygen and the stereochemistry of the complexes are discussed in relation to the elemental analyses and spectra (electronic, infrared and nuclear magnetic resonance).