Schiff-base complexes of calcium: crystal structure analysis of dinitrato[N,N'-propane-1,3-diylbis(salicylideneimine)]calcium(II) and the spectroscopic properties of some related complexes

Abstract

The title compound, [Ca(C 17H 18N202)(NO3)2], C17HlsCaN4Os, is orthorhombic with a = 37.166 (3), b = 10.181 (1), c = 5.111 (0) A, Z = 4, space group P2~2~2~. The structure was refined to R = 0.026 for 1511 counter reflections. The Schiff base is present in a hitherto unreported charge-separated form with the ligand bridging two Ca ions through negatively charged O atoms. The azomethine N atoms are not coordinated; they carry the protons which are transferred from the phenolic groups on complex formation and form intramolecular hydrogen bonds with the O atoms. A bidentate, chelating nitrate ion is coordinated to each Ca ion while a pair of equivalent, bridging nitrate ions complete eight-coordination about Ca u by the formation of chelate rings to the separate Ca ions. The stereochemistry around Ca is best described as a distorted hexagonal bipyramid. Nine Schiff-base complexes have been prepared with N, N'-propane-l,3-diylbis(salicylideneimine) Since the infrared spectra of the coordinated Schiff bases are so similar, it is concluded that the complexes are closely related structurally. The mode of coordination of Schiff bases in a large number of similar compounds of other metal ions is discussed.

Synthesis and characterization of tribenzyltin(IV) and dibenzyltin(IV) complexes of 2-{[(2Z)-3-hydroxy-1-methyl- 2-butenylidene]amino}acetic acid: Crystal structure of tribenzyl{2-{[(2Z)-3-hydroxy-1-methyl-2-butenylidene] amino}acetato}tin(IV)

“…The magnitudes of these hydrogen-bonding interactions are similar those reported for an analogous Schiff base complex [15]. Such proton transfer from oxygen to nitrogen atoms via hydrogen bond, and the formation of zwitterions in similar molecules to that discussed here, is quite commonly encountered [6,16,17] and facilitates coordination of the alkoxy or phenolic oxygens with the tin atoms.…”

Molecular adduct of dimethyltin dichloride with 2-(p-methoxyphenyliminomethyl)phenol, [SnCl2(CH3)2(C14H13NO2)2]

“…However, Saraswat, Srivastava & Mehrotra (1979) from essentially identical infrared results reported that only the phenolic O atoms from the ligands are coordinated in the complexes, indicating that the intermediate zwitterion (lb) is predominant in the phenolimine (la)/ketoenamine (lc) equilibrium of Schiff bases. This is further substantiated by Bullock, Ladd, Povey & Tajmir-Riahi (1979) from the crystal structure and spectroscopic study of Schiff-base complexes of calcium nitrate.…”

A Fourier transform infrared study of the electrophilic attack at the N7-site of guanosine-5′-monophosphate

“…with the C=N+ frequencies, which were experimentally found (27,28) to be higher than the parent C=N groups. A strong absorption band at 1359 cm-' in the spectrum of the free base related to a pyrimidinic ring vibration (29) lost intensity and shifted to a higher frequency (1369 cm-') upon protonation.…”