Structure−Spectroscopy Correlation in Distorted Five-Coordinate Cu(II) Complexes:  A Case Study with a Set of Closely Related Copper Complexes of Pyridine-2,6-dicarboxamide Ligands

Abstract

Eight Cu(II) complexes with the [Cu(dmppy)] moiety (dmppyH(2) = tridentate ligand N,N'-dimethylpyridine-2,6-dicarboxamide; H's are dissociable amide protons) and ligands like pyridine, water, N-methylimidazole, substituted and unsubstituted o-phenanthroline, and bipyridine have been isolated and structurally characterized. The basal angles of these structurally related five-coordinate Cu(II) complexes (and two previously reported ones) correlate well with the EPR hyperfine splitting parameter A( parallel). However, the values of the parameter tau which provides a measure of the degree of square pyramid versus trigonal bipyramid geometry adopted by these complexes do not correlate linearly with the A( parallel) values. It is evident that out-of-plane distortions and ligand strain make calculation of tau inconsistent in certain sets of five-coordinate Cu(II) complexes. Structure-spectroscopy correlation involving tau is not feasible in such cases.

Metal ion binding patterns of acyclovir: Molecular recognition between this antiviral agent and copper(II) chelates with iminodiacetate or glycylglycinate

“…Other remarkable structural features are the following: 1) The trans-angles of the basal planes are quite dissimilar [θ(N1-Cu1-N37) 177.89 (19)º and φ(O11-Cu1-O21) 148.66 (14)º] so that the Addison parameter τ =[(θ−φ) / 60] has a value of (0.49), very close to 0.5. That represents a halfway distortion point between regular square based pyramidal coordination (with θ = φ and τ = 0) and bi-pyramidal trigonal coordination (where θ − φ =(180-60)º = 60º and τ =1) [38]. 2) The mean basal coordination plane (defined by the three donors of IDA involved in chelation and the N7(acv) donor) and the mean guanine-like(acv) plane define a rather open dihedral angle (30.3º-see supplementary material S.1.4.…”

Heterolytic Cleavage of the C−C Bond of Acetonitrile with Simple Monomeric CuII Complexes: Melding Old Copper Chemistry with New Reactivity

“…We speculated that the instability and/or reactivity of [Cu II (dmppy)(L)] complexes in solution may be due to severe out-of-plane distortion of the Cu II ion from the dmppy 2À plane. [8] The highly basic nature of the dmppy 2À ligand could be another contributing factor for this reactivity. Here we report the synthesis and structure of [Cu(dmppy)(en)] (en ethylenediamine) and describe its reactivity toward CH 3 CN.…”

“…The complex [Cu(dmppy)(en)] was synthesized from [{Cu(dmppy)(py)} 2 ] [8] and ethylenediamine in DMF.…”

“…Although [Cu(en) 3 ][Cu(CN) 3 ] has been synthesized previously, [11] and the structures of the individual ions [Cu(en) 3 ] 2 [12,13] and [Cu(CN) 3 ] 2À [14,15] have been determined separately in with CH 3 CN and ethylenediamine is slow mainly due to its low solubility under the conditions used, and also appears to be quite complex in nature (Scheme 1). Analogous complexes such as [Cu(dmppy)-(bpy)], [8] which are soluble in CH 3 CN, react faster in the en/ CH 3 CN mixture and cleave CH 3 CN at a faster rate (1 ± 2 days). The isolation of [Cu(en) 3 ][Cu(CN) 3 ] indicates that cleavage of CH 3 CN must be heterolytic due to the presence of CN À in the products.…”

Synthesis, Characterization and Coordination Chemistry of N,N'-bis(3-pyridylmethyl)benzene-1,4-dicarboxamide with Palladium and Ruthenium Salts

“…It was reacted with terephthaloyl chloride, 3-pyridylamine and triethylamine. Triethylamine acts as a base [8,9] to increase the effectiveness of nucleophilic substitution of the amines. The mechanism of the reaction is suggested in Scheme-I.…”