Polysulfonylamine, CL [1]. Wasserstoffbrücken in kristallinen Oniumdimesylamiden: Ein robustes Achtring-Synthon in den Strukturen von Methyluronium- und 1,1-Dimethyluronium-dimesylamid./Polysulfonylamines, CL [1]. Hydrogen Bonding in Crystalline Onium Dimesylamides: A Robust Eight-Membered Ring Synthon in the Structures of Methyluronium and 1,1-Dimethyluronium Dimesylamide

Abstract

Methyluronium dimesylamide (1) and 1,1-dimethyluronium dimesylamide (2) have been prepared by proton transfer reactions of the strong nitrogen acid HN(SO2Me)2 with the corresponding ureas and characterized by low-temperature X-ray diffraction (1: orthorhombic, space group P212121, Z′ = 1; 2: orthorhombic, Pna21, Z′ = 2). Compound 2 appears to be the first crystallographically established 1,1-dimethyluronium salt. As a common feature, the three independent formula units consist of ion pairs held together by an eight-membered ring synthon [N2 = R2 2(8), antidromic] constructed from a syn,syn-sequence H-O-C(sp2)-N-H ofthe cation and a V-shaped O-S(sp3)-N fragment of the anion via homonuclear two-centre hydrogen bonds. The surplus N-H donors form hydrogen bonds to O=S acceptors in adjacent formula units, leading to a three-dimensional network (1) or a pseudo-21 symmetric helical catemer ofalternatingly inequivalent formula units (2). In both structures, the activated methyl groups give rise to numerous short interionic C-H···O contacts, the more prominent of which are analyzed in terms ofweak hydrogen bonding [cut-off criteria: d(H···O) ≤ 270 pm, θ(C-H···O) ≥130°].