Synthesis and Structure of Monomeric, Trimeric, and Mixed Phenylcyanamides

Abstract

In a new synthetic approach phenylcyanamide (Hpca) was synthesized by methylation of phenylthiourea followed by a basic work-up. All products along the synthetic route have been fully characterized by means of NMR, IR, and X-ray studies. The first structural report of neutral mixed crystals of phenylcyanamide containing monomeric and trimeric Hpca is presented. Examination of these intriguing mixed crystals revealed the formation of distinct layers of monomeric and trimeric Hpca. These layers are interconnected by weak hydrogen bonds. The trimer represents triphenylisomelamine, which readily isomerizes to the triphenylmelamine in the melt, in accord with computations at the B3LYP level, indicating an exothermic process (DeltaH = -49.4 kcal mol(-1)). Pure trimeric Hpca (triphenylisomelamine) was obtained either by recrystallization of the mixed crystals from boiling water or by trimerization of monomeric Hpca in isopropanol for 12 h under reflux conditions. For comparison tritylcyanamide (Htca) and potassium phenylcyanamide as an [18]crown-6 complex [K([18]crown-6)pca] have been synthesized, and the solid-state structures were determined using X-ray diffraction techniques. The thermal behavior was studied by thermo-analytical experiments. In agreement with the experimental results, computations predict an exothermic cyclotrimerization process for Hpca (DeltaH = -41.3 kcal mol(-1)).

Salts and Ionic Liquids of Resonance Stabilized Amides

“…Although phenylformylcyanoamide is neither hygroscopic nor air sensitive, it should be stored under inert gas since it slowly decomposes in the presence of moisture according to Equation (10). The labile phenylcyanoamide reacts further to give the trimer 53 …”

“…Köhler and Jäger were the first who addressed explicitly the carbodiimide/dicyanoamide problem as they studied phenyldicyanoamide and phenylcyanocarbodiimide 63. We prepared phenyldicyanoamide in a slightly modified synthetic procedure from potassium phenylcyanoamide53 and cyanogen bromide in acetonitrile (Scheme ) and recrystallized from chloroform.…”

Ionic Liquids Containing the Triply Negatively Charged Tricyanomelaminate Anion and a B(C6F5)3 Adduct Anion

“…[4a] In the last decade, this trimerization process leading to promising melaminate salts has been of great interest to several groups. [4][5][6] In addition, the synthesis and structural investigations of a series of hitherto unknown dicyanoamide salts (alkaline earth metal, [7] ammonium, [8] guanidinium, [9] rare earth metals, [10] and guanylurea [11] ) have been reported recently. Schnick et al showed that trimerization of Na[N(CN) 2 ] (NaA C H T U N G T R E N N U N G [dca]) irreversibly occurs above 380 8C.…”

“…Interestingly, Madelung and Kern observed the trimerization of sodium dicyanoamide Na[N(CN) 2 ] at “dark red heat” and isolated the trimerization product sodium melaminate Na 3 [C 3 N 6 (CN) 3 ] after recrystallization from water (Scheme ) 4a. In the last decade, this trimerization process leading to promising melaminate salts has been of great interest to several groups 4–6. In addition, the synthesis and structural investigations of a series of hitherto unknown dicyanoamide salts (alkaline earth metal,7 ammonium, [8] guanidinium,9 rare earth metals,10 and guanylurea11) have been reported recently.…”

Cyanidosilikate – Synthese und Struktur

“…die Schwingungsdaten von einem angenommenen [Si{NCCr(CO) 5 } 6 ] 2− ‐Komplexion mit einem Si(NC) 6 ‐Kern beschrieben . Unserem Interesse an der Pseudohalogenchemie (insbesondere an Cyanid/Halogenid‐Austauschreaktionen) folgend, möchten wir hier über die Synthese von Salzen mit [SiF(CN) 5 ] 2− ‐ und [Si(CN) 6 ] 2− ‐Dianionen berichten und damit diese Lücke in der Hauptgruppenchemie schließen.…”