Versatile coordination architectures of products generated by the in situ reaction of a doubly bis(2-pyridyl)pyrazolate bridged dinuclear copper(II) complex with tetracyanoethylene

摘要

The reaction of a doubly bis.2-pyridyl) pyrazolate (bpypz(-)) bridged dinuclear copper.II) complex, [Cu-2(bpypz)(2)](2+), with neutral tetracyanoethylene (TCNE) results in the formation of [Cu-4(bpypz)(4)(TCVA)(2)] center dot 2TCVA (1) in tetrahydrofuran (THF), syn-[Cu2.bpypz) 2.DCNM) 2] (2) in MeOH, and anti-[C-2(bpypz)(2)(DCNE)(2)] (3) in EtOH, where TCVA(-)= 1,2,2-tricyanoethenolate, DCNM-= 2,2-dicyano-1-methoxyethenolate, and DCNE-= 2,2-dicyano-1-ethoxyethenolate. The ligands TCVA-, DCME-, and DCNE-in 1-3 were formed in situ during the reaction in different solvents, and the ligands were confirmed through infrared spectroscopy, single-crystal X-ray diffraction, and elemental analyses. The single-crystal X-ray structures of 1-3 show that each copper.II) centre is five-coordinate in an approximately square pyramidal geometry. 1 is a discrete dimer-of-dimers type tetranuclear complex with the copper.II) centres bridged by two trans-mu 2-N, O-TCVA-. 2 and 3 are discrete dinuclear complexes. In 2, two apically monodentate N-coordinated DCNM-molecules are oriented in a cis manner to one another, consequently adopting a syn-orthogonal configuration. A weak interaction exists between each copper.II) centres and the O atoms of the apically coordinated DCNM-molecules of the neighbouring copper.II) dinuclear units, resulting in a pseudo onedimensional ladder-like coordination polymer arrangement. In 3, two apically monodentate N-coordinated DCNE-molecules are oriented in a mutually trans manner across the basal plane of [Cu-2(bpypz)(2)](2+), thereby adopting an anti-orthogonal configuration. Continuous wave X-band electron paramagnetic resonance spectral measurements on finely ground polycrystalline samples of 1-3 confirm a thermally depopulated S = 1 triplet state arising from antiferromagnetically coupled two S = 1/2 spins with orthorhombic g values. Variable-temperature dc magnetic susceptibility measurements of 1-3 indicate significant antiferromagnetic coupling (quantified by the isotropic spin Hamiltonian, H =-2JS(1)center dot S-2, for the two copper.II) centres: J =-217.7,-210.3, and-188.5 cm-1 for 1, 2 and 3, respectively) for the doubly bpypz bridged copper(II) centres.