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

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 massspectroscopy. The factors influencing the formation and stability of heterometallic complexes originating from the reactions of divalent metal acetylacetonates with metal isopropoxides are discussed.