Coordination of mono- and diamines to titanium and zirconium alkoxides

Abstract

The structural chemistry of crystalline adducts M2(OR)8(amine)2 (M = Ti: OR = OiPr, amine = NH2CH2Ph, NH2Bu; M = Ti: OR = OEt, amine = piperidine; M = Zr: OR = OiPr, amine = NH2CH2Ph, NH2C6H11) is discussed. The adducts were obtained by reaction of Ti(OEt)4 or M(OiPr)4 with primary or secondary amines. The monoamine adducts are centrosymmetric dimers in which the amines are coordinated axially to the M2μ-OR)2 ring and hydrogen-bonded to neighboring alkoxo ligands. The adducts are sufficiently stable if the hydrogen bond is strong. 15N NMR studies revealed that the amines are also coordinated in solution. Coordination polymers were obtained when diamines with two terminal NH2 groups are reacted with Ti(OiPr)4. The general structure is the same as that of Ti2(OiPr)8(RNH2)2. However, the diamines bridge the Ti2(OiPr)8 units. When Zr(OiPr)4 was reacted with NH2CH2CH2NHMe, the adduct Zr2(OiPr)8[NH2CH2CH2NHMe]2 was obtained where only the NH2 group is coordinated.