X-ray crystallographic, spectroscopic, and electrochemical properties of Group 12 metal-chlorides of di-2-pyridyl ketone acetic acid hydrazone (dpkaah)

• Published in: Journal of coordination chemistry Vol. 71; no. 15; pp. 2322 - 2339
• Main Authors: Bakir, Mohammed, Lawrence, Mark A. W., Conry, Rebecca R.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 03-08-2018; Taylor & Francis Ltd
• Subjects: Acetic acid; Acids; Cadmium; Carbonyl groups; Carbonyls; Chlorides; Crystal structure; Crystallography; Di-2-pyridyl ketone acetic acid hydrazone; Electrochemical analysis; electrochemistry; Ethanol; Hydrazones; Low concentrations; Refluxing; Single crystals; Spectrophotometry; spectroscopy; Stability; Structural analysis; synthesis; X-ray; Zinc
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2018.1471685

Di-2-pyridyl ketone acetic acid hydrazone hydrate, dpkaah.0.5H
2
O (1), prepared from the acid catalyzed condensation of di-2-pyridyl ketone (dpk) with acetic acid hydrazide in refluxing ethanol, undergoes facile coordination to Group 12 metal-chlorides in CH
3
CN to form [MCl
2
(κ
3
-N,N,O-dpkaah)] {M=Zn (3), Cd (4) or Hg(5)}. X-ray structural analysis on single crystals of dpkaah (2) and 3-5 confirmed their identities and revealed pseudo-coordination of the carbonyl group (C=O). Infrared measurements confirmed the pseudo-coordination of the carbonyl group to MCl
2
. The geometries of 3-5 vary, while 5 adopts a square pyramidal geometry, 4 has a structure halfway between square pyramidal and trigonal bipyramidal and 3 is less distorted from square pyramidal than 3. The extended structures of 3-5 exposed extensive networks of non-covalent interactions, and in the case of 4 chloride bridges of the type Cd(μ-Cl)
2
Cd were observed. Spectroscopic measurements in different solvents and variable temperature studies confirmed the stability of the keto form of 1 and 3-5. Spectrophotometric titrations of protophilic solutions (dmf or dmso) of 1 with MCl
2
revealed facile coordination of MCl
2
to 1 and disclosed low concentrations of MCl
2
can be detected and determined using protophilic solutions of 1. Electrochemical measurements on dmf solutions divulged electrochemical decomposition of uncoordinated 1, the facile coordination of 1 to MCl
2
, and the stability of 3-5 decreases as the size of the metal ion increases.