Zinc and Cobalt Complexes Derived from Tetradentate Tripodal Ligands with N 2 O 2 Donorset as Model Compounds for Phosphatases

Starting from the tripodal tetradentate ligands ‐(3,5‐dibromo‐2‐hydroxybenzyl)(2‐hydroxybenzyl)(2‐pyridyl)methylamine (H 2 L1), (3,5‐dibromo‐2‐hydroxybenzyl)(2‐hydroxy‐5‐nitrobenzyl)(2‐pyridyl)methylamine (H 2 L2), and (3,5‐dichloro2‐hydroxybenzyl)(2‐hydroxy‐5‐nitrobenzyl)(2‐pyridyl)methylamine (H 2 L3) the new isostructural dinuclear zinc compounds [Zn 2 (L1) 2 ]·N(CH 2 CH 3 ) 3 ( 1 ), [Zn 2 (L2) 2 ]·2CH 3 OH ( 2 ) and [Zn 2 (L3) 2 ]·C 4 H 10 O ( 3 ) were synthesized. Due to their enzyme‐like trigonal bipyramidal N 2 O 3 coordination environment of the zinc ions and the similar Zn···Zn distances the complexes can be considered to be structural models for the active sites in phospholipase C and nuclease P1. With H 2 L3 also the dinuclear complex [Co 2 (L2) 2 (CH 3 OH)]·2CH 3 OH·0.5C 4 H 10 O ( 4 ) could be prepared. The new compounds were isolated and characterized by single crystal X‐ray crystallography as well as infrared spectroscopy. The cobalt compound 4 was additionally characterized by UV‐Vis spectroscopy and magnetic measurements. 1 crystallizes in the monoclinic space group P2 1 /n with a = 11.2814(2), b = 28.6154(2), c = 13.1866(3) Å, β = 96.995(1)°, V = 4225.2(2) Å 3 , Z = 4. 2 and 3 are monoclinic, space group C2/c with a = 23.084(5), b = 9.232(2), c = 21.849(4) Å, &β; = 96.83(3)°, V = 4623(2) Å 3 , Z = 4, and a = 22.7834(3), b = 9.2463(1), c = 21.6351(3) Å, &β; = 97.592(1)°, V = 4517.7(2) Å 3 , Z = 4, respectively. 4 crystallizes in the monoclinic space group I2/a with a = 22.4680(4), b = 20.5517(4), c = 22.8910(6) Å, &β; = 111.938(1)°, V = 9804.7(4) Å 3 , Z = 8. 4 shows an effective magnetic moment of 6.72 μ B at 300 K which clearly indicates the presence of two cobalt(II) high spin ions with Curie‐Weiss behaviour above 80 K. At lower temperatures a decrease of the effective magnetic moment was observed.