Structures and properties of zinc(II) complexes of NN-bis[(2-hydroxy-5-X-phenyl)phenylmethylene]-4-azaheptane-1,7-diamine (X = chloro or methyl): comparison of d10, d9, and d8 analogues

Abstract

The zinc (II) complexes of the quinquedentate ligands derived from the Schiff-base condensation of 3,3′-iminobis (propylamine) with 5-chloro-2-hydroxybenzophenone (cbp) and 2-hydroxy-5-methylbenzophenone (mbp) have been synthesized and their crystal structures determined. [Zn(cbp)]· H₂O Is crystallographically isomorphous with [Cu(mbp)] and the co-ordination environment of the zinc is a distorted trigonal bipyramid. The water molecule is disordered; it is remote from the metal atom and appears to produce no significant distortion of the complex. The striking differences between the related nickel(II), copper(II), and zinc(II) complexes must be ascribed mainly to the dⁿ configuration of the metals. The metal environment in related nickel(II), copper(II), and zinc(II) complexes lies between trigonal bipyramidal and distorted square pyramidal, and progresses increasingly towards bipyramidal through the series Cu, Ni, Zn.

Crystals of the zinc(II) complex with mbp were obtained as a hydrate [Zn(mbp)]·H₂O with the water molecule probably hydrogen-bonded to a ligand atom, but with no apparent distortion due to the water molecule. The metal environment again approximates a trigonal bipyramid.

The crystal structures were determined from full-matrix least-squares refinement of counter data ([Zn(cbp)]·H₂O: space group P, Z= 2, a= 10.099(1), b= 12.500(2), c= 13.261(4)Å, α= 74.57(3), β= 68.06(1), γ= 86.07(2)°, R= 0.036, 2 612 reflections; [Zn(mbp)] H₂O : space group P2₁/c, Z= 4, a= 16.30(1), b= 10.178(4), c= 18.996(9)Å, β= 71.79(9)°, α=γ= 90, R= 0.048, 2 669 reflections).