Anion‐Directed Template Synthesis and Hydrolysis of Mono‐Condensed Schiff Base of 1,3‐Pentanediamine and o‐Hydroxyacetophenone in NiII and CuII Complexes

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Abstract
Bis(o‐hydroxyacetophenone)nickel(II) dihydrate, on reaction with 1,3‐pentanediamine, yields a bis‐chelate complex [NiL2]·2H2O (1) of mono‐condensed tridentate Schiff baseligand HL {2‐[1‐(3‐aminopentylimino)ethyl]phenol}. The Schiff base has been freed from the complex by precipitating the NiII as a dimethylglyoximato complex. HL reacts smoothly with Ni(SCN)2·4H2O furnishing the complex [NiL(NCS)] (2) and with CuCl2·2H2O in the presence of NaN3 or NH4SCN producing [CuL(N3)]2 (3) or [CuL(NCS)] (4). On the other hand, upon reaction with Cu(ClO4)2·6H2O and Cu(NO3)2·3H2O, the Schiff base undergoes hydrolysis to yield ternary complexes [Cu(hap)(pn)(H2O)]ClO4 (5) and [Cu(hap)(pn)(H2O)]NO3 (6), respectively (Hhap = o‐hydroxyacetophenone and pn = 1,3‐pentanediamine). The ligand HL undergoes hydrolysis also on reaction with Ni(ClO4)2·6H2O or Ni(NO3)2·6H2O to yield [Ni(hap)2] (7). The structures of the complexes 2, 3, 5, 6, and 7 have been confirmed by single‐crystal X‐ray analysis. In complex 2, NiII possesses square‐planar geometry, being coordinated by the tridentate mono‐negative Schiff base, L and the isothiocyanate group. The coordination environment around CuII in complex 3 is very similar to that in complex 2 but here two units are joined together by end‐on, axial‐equatorial azide bridges to result in a dimer in which the geometry around CuII is square pyramidal. In both 5 and 6, the CuII atoms display the square‐pyramidal environment; the equatorial sites being coordinated by the two amine groups of 1,3‐pentanediamine and two oxygen atoms of o‐hydroxyacetophenone. The axial site is coordinated by a water molecule. Complex 7 is a square‐planar complex with the Ni atom bonded to four oxygen atoms from two hap moieties. The mononuclear units of 2 and dinuclear units of 3 are linked by strong hydrogen bonds to form a one‐dimensional network. The mononuclear units of 5 and 6 are joined together to form a dimer by very strong hydrogen bonds through the coordinated water molecule. These dimers are further involved in hydrogen bonding with the respective counteranions to form 2‐D net‐like open frameworks. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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