Synthesis and Characterization of Structurally Diverse Alkaline-Earth Salen Compounds for Subterranean Fluid Flow Tracking

Abstract

A family of magnesium and calcium salen-derivatives was synthesized and characterized for use as subterranean fluid flow monitors. For the Mg complexes, di- n-butyl magnesium ([Mg(Bu )]) was reacted with N, N'-ethylene bis(salicylideneimine) (H-salen), N, N'-bis(salicylidene)-1,2-phenylenediamine (H-saloPh), N, N'-bis(3,5-di- t-butylsalicylidene)-ethylenediamine (H-salo-Bu ), or N, N'-bis(3,5-di- t-butylsalicylidene)-1,2-phenylenediamine (H-saloPh-Bu ), and the products were identified by single-crystal X-ray diffraction as [(κ-(O,N,N'),μ-(O')saloPh)(μ-(O),(κ-(N,N'),μ-(O')saloPh)(μ-(O),κ-(N,N',O')saloPh')Mg]·2tol (1·2tol; saloPh' = an alkyl-modified saloPh derivative generated in situ), [(κ-(O,N,N',O')saloPh)Mg(py)]·py (2·py), [(κ-(O,N,N',O')salo-Bu )Mg(py)] (3), [(κ-(O,N,N',O')saloPh-Bu )Mg(py)]·tol (4·tol), and [(κ-(O,N,N'),μ-(O')saloPh-Bu )Mg] (5), where tol = toluene; py = pyridine. For the Ca species, a calcium amide was independently reacted with H-salo-Bu and H-saloPh-Bu to generate the crystallographcially characterized compounds: [(κ-(O,N,N',O')salo-Bu )Ca(py)] (6), [(κ-(O,N,N',O')saloPh-Bu )Ca(py)]·py (7·py). The bulk powders of these compounds were further characterized by a number of analytical tools, where 2-7 were found to be distinguishable by Fourier transform infrared and resonance Raman spectroscopies. Structural properties obtained from quantum calculations of gas-phase analogues are in good agreement with the single-crystal results. The potential utility of these compounds as taggants for monitoring subterranean fluid flows was demonstrated through a series of experiments to evaluate their stability to high temperature and pressure, interaction with mineral surfaces, and elution behavior from a loaded proppant pack.

Recent developments in penta-, hexa- and heptadentate Schiff base ligands and their metal complexes

“…In addition, most of Schiff bases have the fascinating abilities to coordinate with metallic ions to form their corresponding complexes of main group, transition metal and lanthanide and actinides elements, with their properties being significantly improved by coordinating to the metal ion [38][39][40]. This ability is due to their stereoelectronic and flexible structures leading to highly versatile coordination compounds with a broad scope of applications rranging from subterranean fluid flow tracking [41,42] to bioinorganic and medicinal chemistry [43,44]. For instance, in the rational design of metal-based therapeutics, Meade and co-workers developed a serries of N-heterocyclic cobalt(III) Schiff base Complexes as potent enzyme and transcription factor inhibitors [45].…”

Compartmentalization of Alkaline-Earth Metals in Salen-Type Cu- and Ni-Complexes in Solution and in the Solid State

“…The choice of a versatile organic ligand with specific coordination sites is thus of crucial importance for the synthesis of such compounds. 32,52…”

“…53,54,63−69,55−62 However, even though transition-metal ions have been widely used in combination with salen-derived ligands for multiple purposes, systems with alkaline-earth-metal ions were poorly investigated. 52,70…”

Homoleptic CoII, NiII, CuII, and ZnII Complexes Based on 8‐Hydroxylquinoline Schiff Base Derivative: a Combined Synthetic, Spectral, Structural, and Magnetic Study

“…Due to their highly modular synthesis allowing the control of the nature of donor atoms, chelating ability, as well as their electronic and steric properties, Schiff base ligands can readily form stable complexes with most of the transition metals in various oxidation states and multiple forms of coordination towards the metallic ions , . Consequently, Schiff base complexes have found applications in different branches of science such as catalysis, magnetism, sensing,, optical,, and energy sciences, as well as medicinal chemistry , …”

“…Among the Schiff bases, N 2 O 2 tetradentate based salen‐type ligands where H 2 ‐salen [ N , N ‐bis(salicylidene)ethylenediamine] is the quintessential representative of this class of symmetrical d i ‐imines compounds, continue to be the most popular and the most studied ones , . They are generally prepared in high yields by condensation of any primary diamine with two equivalents of salicylaldehyde derivatives , .…”