{μ-6,6′-Dieth­oxy-2,2′-[ethane-1,2-diylbis(nitrilo­methyl­idyne)]diphenolato}trinitratoholmium(III)nickel(II)

In the title heteronuclear Ni(II)–Ho(III) complex (systematic name: {μ-6,6′-dieth­oxy-2,2′-[ethane-1,2-diylbis(nitrilo­methyl­idyne)]diphenolato-1κ(4) O (1),O (1′),O (6),O (6′):2κ(4) O (1),N,N′,O (1′)}trinitrato-1κ(6) O,O′-holmium(III)nickel(II)), [HoNi(C(20)H(22)N(2)O(4))(NO(3))(3)], with the hexa­dentate Schiff base compartmental ligand N,N′-bis­(3-ethoxy­salicyl­idene)ethyl­enediamine (H(2) L), the Ho and Ni atoms are doubly bridged by two phenolate O atoms of the Schiff base ligand. The coordination of Ni is square-planar with the donor centers of two imine N atoms and two phenolate O atoms. The holmium(III) center has a tenfold ­coordination environment of O atoms, involving the phenolate O atoms, two eth­oxy O atoms and two O atoms each from the three nitrates. Weak C—H⋯O and O⋯Ni [3.383 (4) Å] inter­actions generate a two-dimensional zigzag sheet.