Interaction of some divalent metal acetylacetonates with Al, Ti, Nb and Ta isopropoxides. Factors influencing the formation and stability of heterometallic alkoxide complexes

Abstract

Interaction of Co(acac)₂ with 2 eq. of Ti(OⁱPr)₄ in hexane leads to an equimolar mixture of the new heterometallic complex [Co₂Ti₂(acac)₂(OⁱPr)₁₀] (1) and the known heteroleptic alkoxide Ti₂(acac)₂(OⁱPr)₆. When redissolved in ⁱPrOH 1 is destroyed, forming [Co₂(acac)₄(ⁱPrOH)₂] (2) as the only isolable crystalline product. Reaction of Co(acac)₂ with 3 eq. of Ta(OⁱPr)₅ gives [Co₂Ta₂(OⁱPr)₁₄] (3) together with Ta(acac)(OⁱPr)₄. Reaction of Ni(acac)₂ with 4 eq. of Nb(OⁱPr)₅ produces the heterometallic complex [NiNb₂(OⁱPr)₁₂] (4). Reactions of M(acac)₂ (M = Co, Ni, Mg and Zn) with Al(OⁱPr)₃ in 1 ∶ 2 ratios provides access to [MAl₂(OⁱPr)₄(acac)₄] [M = Co (5), Ni (6), Mg (7)] and [Zn₂Al₂(OⁱPr)₆(acac)₄] (8) respectively. When redissolved in ⁱPrOH, [NiAl₂(OⁱPr)₄(acac)₄] (6) is destroyed, forming a mixture of [Ni₂(acac)₄(ⁱPrOH)₂] (9), Al(OⁱPr)₃ and Al(acac)₃. Interaction of M(acac)₂, (M = Co, Ni) with metal isopropoxides in ⁱPrOH as well as their recrystallization from ⁱPrOH give 2 and 9 respectively. 5–7 are unstable in the hydrocarbon solution on heating, decomposing with formation of [M₂Al₂(OⁱPr)₆(acac)₄], along with Al(acac)₃ and heterometallic alkoxide species. Mg(acac)₂ was found to recrystallize unchanged from the solutions of Ti(OⁱPr)₄ in toluene. The solution structure and stability of the heterometallic complexes has been investigated by UV-Vis spectroscopy and NMR, and the details of their decomposition on sublimation by mass-spectroscopy. The factors influencing the formation and stability of heterometallic complexes originating from the reactions of divalent metal acetylacetonates with metal isopropoxides are discussed.