Unraveling the Synthesis of SbCl(C3N6H4): A Metal-Melaminate Obtained through Deprotonation of Melamine with Antimony(III)Chloride

Abstract

The discovery of melamine by Justus von Liebig was fundamental for the development of several fields of chemistry. The vast majority of compounds with melamine or melamine derivatives appear as adducts. Herein, we focus on the development of novel compounds containing anionic melamine species, namely the melaminates. For this purpose, we analyze the reaction of SbCl3 with melamine by differential scanning calorimetry (DSC). The whole study includes the synthesis and characterization of three antimony compounds that are obtained during the deprotonation process of melamine to melaminate with the reaction sequence from SbCl4(C9N18H19) (1) via (SbCl4(C6N12H13))2 (2) to SbCl(C3N6H4) (3). Compounds are characterized by single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), and infrared spectroscopy (IR). The results give an insight into the mechanism of deprotonation of melamine, with the replacement of one, two, or eventually three hydrogen atoms from the three amino groups of melamine. The structure of (3) suggests that metal melaminates are likely to form supramolecular structures or metal-organic frameworks (MOFs).

Thermal deprotonation and condensation of melamine in the presence of indium(iii)chloride

“…Given that all the compounds contain NH 2 groups, it is not surprising that they exhibit similar patterns in the regions between 3500–3200 cm −1 and 1580–1600 cm −1 , ascribed to NH stretching and bending vibrations, respectively. 17,28 However, apart from slight variations in relative intensities and splitting, there is a distinctive difference in (NH 4 )[(InCl 2 ) 3 (C 12 N 20 H 8 )]·⅔[InCl 3 (NH 3 )] compound compared to melem, and melamine in these regions. In fact, in the spectrum of the (NH 4 )[(InCl 2 ) 3 (C 12 N 20 H 8 )]·⅔[InCl 3 (NH 3 )] compound, the band at around 3500–3200 cm −1 appears broader and slightly less intense compared to the two others, which can signify differences in structures, especially the number of NH 2 groups present in this structure.…”

“…As expected, the compounds show a similar spectrum in the regions around 800 cm −1 and 1400–1550 cm −1 , which are related to ring out-of-plane bending and side chain C–N breathing, respectively. 28…”

“…Exploring the realm of C/H/N chemistry, melamine, protonated melamine, and melaminate compounds present intriguing aspects. 27,28 Melamine exhibits the ability to coordinate with metal halides, forming compounds like [Cu 3 Cl 3 (C 3 N 6 H 6 )] n , 29 [Cu 2 Br 2 (C 3 N 6 H 6 )] n , 29 the silver complex [Ag(C 3 N 6 H 6 )(H 2 O)(NO 3 )] n , 30 [Ag(C 3 H 6 N 6 )]NO 3 , 31 and the mercury compound (C 3 N 6 H 7 )(C 3 N 6 H 6 )HgCl 3 . 25 However, compounds involving deprotonated melamine are of heightened interest compared to these adducts.…”

“…Noteworthy examples include K(C 3 N 6 H 5 )·NH 3 , Rb(C 3 N 6 H 5 )·½NH 3 , 32 K 3 (C 3 N 6 H 3 ), 33 Cu 3 (C 3 N 6 H 3 ), 27 SbCl 4 (C 9 N 18 H 19 ), (SbCl 4 (C 6 N 12 H 13 )) 2 , and SbCl(C 3 N 6 H 4 ). 28…”