Heavier alkali metal complexes of 2-phenylamidopyridine: An X-ray crystallographic and theoretical study of a structurally diverse series of crown ether adducts

Abstract

Complexes of the anion of the secondary amine 2-phenylaminopyridine (LH) with the heavier alkali metals Na-Cs have been prepared in the presence of various macrocyclic polyether crowns [12-crown-4 (12C4), 15-crown-5 (15C5), and 18-crown-6 (18C6)], which coordinate to the metal ions in all cases. Depending on the combination of alkali metal and crown, the products include separated ion pairs [(crown)(2)M](+)L(-)(12C4/Na, 15C5/K, 15C5/Rb, 15C5/Cs) and contact-ion-pair neutral molecules [(crown)ML](15C5/Na, 18C6/Na, 18C6/K, 18C6/Rb) in which L(-) acts as a bidentate ligand. [((12C4)KL)(2)] is a dimer in which the amido and pyridine N atoms of two ligands bridge the metal ions, while [((18C6)KL(2)K)([infinity])] is a chain polymer with crown O and pyridyl N atoms acting as bridges in corner-sharing KOKN four-membered rings and may be regarded as a potassium potassate complex. [((18C6)Cs(2)L(2))([infinity])] is also polymeric, with a basic arrangement like that of [((12C4)KL)(2)], but with each 18C6 ligand mu-kappa6:kappa6 to two metal centres, generating the polymer. Although most of the [(crown)(2)M](+) sandwich cations have essentially parallel crown ligands, [(12C4)(2)Rb](+) is markedly bent, both in the complex incorporating THF as an additional ligand and in the THF-free complex, where two of these cations form a centrosymmetric dimer through two bridging oxygen atoms; DFT calculations indicate that the bending is inherent, thus enabling the coordination by an extra oxygen atom rather than being a consequence of this coordination. Attempts to isolate the caesium 12C4 derivative were unsuccessful. The compounds have been characterized by NMR spectroscopy, CHN microanalysis and, in most cases, X-ray crystallography.

Exploring the solid state and solution structural chemistry of the utility amide potassium hexamethyldisilazide (KHMDS)

“…Three of them are in the range 2.773 2 . Complex 6 is a rare example of a potassium amide 12-crown-4 dimer, only two other examples have been reported with different amides, (2-phenylamido)pyridine 75 and (trimethylsilylamido)pyridine. 76 Complexes 7 and 8 both crystallised in the monoclinic system space group P2 1 /n, whilst 9 crystallised in the triclinic system P1.…”

Reaktionen von 1,3‐Diphenyltriazenid mit Cu+ und Tl+

“…Der Ligand 15‐Krone‐5 bedeckt das Na‐Triazenid‐Assemble halbsandwichartig mit Na–O‐Abständen zwischen 242.5(8) und 262.5(7) pm, was im Rahmen der bisher gemessenen Werte liegt. Eine zu 3 strukturell ähnliche Verbindung ist [Na(15‐Krone‐5)(2‐PhN‐Py)], das ähnliche Na–N‐ und N–O‐Bindungslängen aufweist 9…”

π(Arene) versus donor ligand complexation in the formation of the heterobimetallic lithium–potassium dianion of (S)-N-(α-methylbenzyl)allylamine

“…The K-N distances range from 2.938-2.997 Å and are slightly longer than those found for typical potassium amides (ca. 2.7-2.8 Å ) but are typical of KÁ Á ÁN dative bonding [16]. The Li-N bond distances (N1-Li1, 1.923(7); N2-Li2, 1.914(6) Å ) are typical for lithium amides [17] while the average Li-C bonds in the central cubane (av.…”