Synthesis and Crystal Structures of Nickel(II) and Copper(II) Complexes of Meso‐3,6,6,9‐Tetramethyl‐4,8‐Diazaundecane‐2,10‐Dione Dioxime

The nickel(II) and copper(II) complexes of meso‐3,6,6,9‐tetramethyl‐4,8‐diazaundecane‐2,10‐dione dioxime (meso‐HM‐PAO) have an intramolecular hydrogen bond between cis oxime groups. [Cu(meso‐HM‐PAO‐H)(H₂O)](NCS) crystallizes in space group P2₁/n with a = 7.692(1), b = 12.028(2), c=20.235(3) Å, β=93.03(1)°, Z = 4 and Dc=1.46 g/cm³. The final R value for this complex was 0.034 for 2223 observed reflections with I ≥ 2.5σ (I). The Cu(II) coordination is a distorted square pyramid. The Cu(II) ion is five‐coorinated with the diazadioxime N atoms equatorial and water O atom axial. The Cu(II) is 0.12 Å from the equatorial plane towards the hydrate. The equatorial Cu‐N distances span a narrow range, 1.953(3)‐1.999(3) Å. The axial Cu‐O distance is 2.314(3) Å. The thiocyanate group is almost linear. The intramolecular O ⃛O hydrogen bond length is 2.479(4) Å. [Ni(meso‐HM‐PAO‐H)](ClO₄) crystallizes in space group P2₁/c with a = 14.774(3), b = 12.752(3), c = 20.035(4) Å, β = 92.94(3)°, Z = 8 and Dc = 1.51 g/cm³. The final R value for the complex was 0.053 for 4794 observed reflections with F ≥ 4σ (F). The coordination about Ni(II) is a slightly distorted square plane. The Ni(II) ion is 0.0673(7) Å from the best plane of the four donor nitrogen atoms away from the perchlorate ion. The Ni‐N distances span a narrow range 1.863(4)‐1.927(4) Å. There are two molecules per asymmetrical unit resulting in eight molecules being packed in an unit cell; they are bound together by van der Waals interactions. The O‐H ⃛O bonds of these complexes give characteristic infrared absorptions as well as chemical shift of the ¹H NMR signal (Ni complex).