Purposeful construction versus self-assembly in approaches to single source precursors of spinel materials. Synthesis, structure and stability studies of (MAl2)-Al-II(acac)(3)((OPr)-Pr-i)(4)(OAc), M-II = Mn, Co, Zn - a new class of heterometallic heteroleptic alkoxide complexes

The reaction of Mn(acac)(3) with 3 eq. of Al((OPr)-Pr-i)(3) in toluene at reflux provided with minor yield single crystals of MnAl2(acac)(3)((OPr)-Pr-i)(4)(OAc)(C7H8)(0.5) (1), incorporating into the molecular structure the acetate ligand originating from oxidation of the (OPr)-Pr-i-groups. 1 was obtained with high yield (76%) via the reaction of Mn(acac)(3) with 2.2 eq. of Al((OPr)-Pr-i)(3) with subsequent addition of 1 eq. of HOAc to the reaction mixture cooled to room temperature. The analogs of 1, CoAl2(acac)(3)((OPr)-Pr-i)(4)(OAc)(C7H8)(0.5) (2), and ZnAl2(acac)(3)((OPr)-Pr-i)(4)(OAc)(C7H8)(0.5) (3), were obtained with almost quantitative yields by reaction of the corresponding M-II(acac)(2) with 2 eq. of Al((OPr)-Pr-i)(3) in toluene at reflux with subsequent addition of 1 eq. of Hacac and 1 eq. of HOAc after cooling the reaction mixture to the room temperature. In the molecules 1-3 the late transition metal atom is tetrahedrally coordinated (eta(2)-acac plus 2 bonds to mu-(OPr)-Pr-i-groups), and the Al atoms have a slightly distorted octahedral coordination (hexacoordinated) (eta(2)-acac plus 3 bonds to mu-(OPr)-Pr-i-groups plus one bond to mu-OAc-group). 1-3 are stable to solvolysis in toluene and are volatile under reduced pressure. Thermal decomposition of CoAl2(acac)(3)((OPr)-Pr-i)(4)(OAc)(C7H8)(0.5) leads to nanoparticles of CoAl2O4, while homogeneous coatings of the spinel can be easily obtained using MOCVD.