Ni(II) complexes as models for inhibited urease

Nickel(II) complexes with the ligands 2,2′-dipyridyl ketone (dpk) and 2,2′-bipyridine (bipy) were prepared in order to study the mode of bonding of hydroxamic acid as secondary ligand. The structures of the novel complexes 1–3 were characterised by X-ray structure determination and IR spectroscopy. [Ni4(dpkOH)4(CH3CO2)4]·4CH3CH2OH (1) is monoclinic, space group P21/c, with a=12.646(3) Å, b=14.031(3) Å, c=18.731(4) Å, β=105.80(3)°. Substitution of 1 equiv. of Ni(CH3CO2)2 by acetohydroxamic acid (aha) results in the formation of [Ni4(dpkOH)2(dpkOCH2CH3)2(CH3CONHO)2]Cl2 (2) (triclinic, space group P, a=10.872(2) Å, b=12.252(2) Å, c=12.348(2) Å, α=76.90(3)°, β=74.70(3)°, γ=76.57(3)°). [Ni2(bipy)2(CH3CO2)3(CH3CONHO)]·CH3CH2OH (3) is triclinic, space group P with a=8.800(2) Å, b=9.193(2) Å, c=22.091(4) Å, α=95.30(3)°, β=92.85(3)°, γ=111.55(3)°). The coordination spheres of 2 and 3 are similar to that found in the active site of the acetohydroxamate-inhibited C319A variant of Klebsiella aerogenes urease.