Synthesis and Structures of 3,5-disubstituted 1,2,4-triazole Head Units and Incorporation of 3,5-dibenzoyl-1,2,4-triazolate into New [2 + 2] Schiff-Base Macrocyclic Complexes

Abstract

The synthesis and characterization of sodium 3,5-diacetyl-1,2,4-triazolate (4 ^Me ) and sodium 3,5-dibenzoyl-1,2,4-triazolate (4 ^Ph ), both of which can be used as head unit building blocks in Schiff-base reactions, are reported. The crystal structures of sodium 3,5-diacetyl-1,2,4-triazolate, as [4 ^Me (H₂O)]_∞, and sodium 3,5-dibenzoyl-1,2,4-triazolate, as [4 ^Ph (CH₃OH)₂]₂, have been determined. The former is a helical polymer whilst the latter is a methanol-bridged dimer. The lead(II) templated cyclization reaction of sodium 3,5-dibenzoyl-1,2,4-triazolate (4 ^Ph ) with 1,3-diaminopropane or 1,4-diaminobutane, respectively, leads to the formation of two new [2 + 2] Schiff-base macrocycles as their lead(II) complexes, [Pb₂ L ^3Ph (μ-OH)]ClO₄ (5) and [Pb₂ L ^4Ph (μ-OH)]ClO₄ (6), respectively. Transmetallation of 5 with nickel(II) ions yields a novel, structurally characterized, dinickel(II) macrocyclic complex, [Ni₂ L ^3Ph (NCS)₂] (7), which features double triazolate bridging of the two five-coordinate nickel(II) ions.

Keywords:

• Triazole
• Macrocycle
• Structure
• Sodium
• Nickel

Acknowledgements

We thank the Marsden Fund (Royal Society of New Zealand) for funding this research, including postdoctoral research fellowships to CDB and UB, and a research assistant position to Mr S. Iremonger. We thank Mr S. Iremonger and Dr M. Weitzer (supported by the Deutsche Akademie der Naturforscher Leopoldina, Germany, BMBF-LPD 9901/8-93) for their help and Dr J. Wikaira and Professor W.T. Robinson (University of Canterbury) for collecting the X-ray data for [4 ^Me (H₂O)]_∞. The University of Otago is thanked for the granting sabbatical leave to SB which facilitated the drafting of this manuscript and for the award of a summer studentship to NGW. JAK is grateful to the Tertiary Education Commission (New Zealand) for the award of a Bright Futures Top Achiever Doctoral PhD scholarship.