Interplay between lead carboxylate and Ti or Zr isopropoxides in solution routes to perovskites:synthesis,molecular structures and reactivity of single source non-oxo Pb-Zr and Pb-Ti carboxylatoalkoxides supported by 2-ethylhexanoate ligands

摘要

The reactions between Ti(O'Pr)_4 and Zr_2(O~iPr)_8(HO~iPr)_2,respectively,and lead 2-ethylhexanoate Pb(O_2CC_7H_(15))_2 have been investigated at rt and by heating.The initial mixed-metal species,characterized by single-crystal X-Ray diffraction,were adducts namely Pb_4Zr_4(mu-O_2CR')_8(mu-OR)_6(mu_3-OR)_2(OR)_8(OHR)_2 1 and Pb_2Ti_4(mu-O_2CR')_4(mu-OR)_6(mu_3-OR)_2(OR)_8 2(R' = CHCH(Et)C_2H_4Me,R = ~iPr)independently of the stoichiometry used.They are the first Pb-Ti and Pb-Zr non-oxo carboxylatoalkoxides reported.1 is also the first Pb-Zr species based on an alkoxide-carboxylate ligand set matching the PbZrO_3 stoichiometry.Both structures are centrosymmetric with six-coordinate transition metals,as required for the perovskite,and are based on triangular M_2Pb cores(M = Zr,Ti).The lead centers display quite high coordination numbers,six and seven.The thermal and hydrolytic condensation reactions of 1 and 2 were investigated.Heat treatment of 2 and elimination of the volatiles under vacuum afforded Pb_2Ti_3(mu_4-O)(mu_3-O)(mu-O_2CC_7H_(15))_2(mu-O~iPr)_6(O~iPr)_4 3 resulting from extrusion of Ti(O~iPr)_4 and scrambling of carboxylate ligands.Characterization of the various compounds was achieved by elemental analysis,FT-IR,~1H and ~(207)Pb NMR.