1. Small Molecule Activation with Intramolecular "Inverse" Frustrated Lewis Pairs
Chamila Manankandayalage, Daniel K Unruh, Clemens Krempner Chemistry. 2021 Apr 7;27(20):6263-6273. doi: 10.1002/chem.202005143. Epub 2021 Mar 5.
The intramolecular "inverse" frustrated Lewis pairs (FLPs) of general formula 1-BR2 -2-[(Me2 N)2 C=N]-C6 H4 (3-6) [BR2 =BMes2 (3), BC12 H8 , (4), BBN (5), BBNO (6)] were synthesized and structurally characterized by multinuclear NMR spectroscopy and X-ray analysis. These novel types of pre-organized FLPs, featuring strongly basic guanidino units rigidly linked to weakly Lewis acidic boryl moieties via an ortho-phenylene linker, are capable of activating H-H, C-H, N-H, O-H, Si-H, B-H and C=O bonds. 4 and 5 deprotonated terminal alkynes and acetylene to form the zwitterionic borates 1-(RC≡C-BR2 )-2-[(Me2 N)2 C=NH]-C6 H4 (R=Ph, H) and reacted with ammonia, BnNH2 and pyrrolidine, to generate the FLP adducts 1-(R2 HN→BR2 )-2-[(Me2 N)2 C=NH]-C6 H4 , where the N-H functionality is activated by intramolecular H-bond interactions. In addition, 5 was found to rapidly add across the double bond of H2 CO, PhCHO and PhNCO to form cyclic zwitterionic guanidinium borates in excellent yields. Likewise, 5 is capable of cleaving H2 , HBPin and PhSiH3 to form various amino boranes. Collectively, the results demonstrate that these new types of intramolecular FLPs featuring weakly Lewis acidic boryl and strongly basic guanidino moieties are as potent as conventional intramolecular FLPs with strongly Lewis acidic units in activating small molecules.
2. 1,4-Dibromo-naphthalene-2,3-diol
Qinghe Gao, Yanping Zhu Acta Crystallogr Sect E Struct Rep Online. 2011 Aug 1;67(Pt 8):o2009. doi: 10.1107/S1600536811026997. Epub 2011 Jul 13.
In the title compound (r.m.s. deviation for the non-H atoms = 0.020 Å), C(10)H(6)Br(2)O(2), an intra-molecular O-H⋯O hydrogen bond generates an S(6) ring. In the crystal, the same H atom also forms an inter-molecular O-H⋯O hydrogen bond, generating a C(2) chain propagating in [100]. The other O-H hydrogen forms a weak O-H⋯π inter-action, and short Br⋯Br contacts [3.5972 (9) Å] also occur.
3. Synthesis and crystal structure of [Zn6Br4(C9H18NO)4(OH)4]·2C3H6O2
Rebecca Scheel, Lukas Brieger, Kathrin Louven, Carsten Strohmann Acta Crystallogr E Crystallogr Commun. 2020 Jun 2;76(Pt 7):998-1002. doi: 10.1107/S2056989020007100. eCollection 2020 Jul 1.
The complete mol-ecule of the hexa-metallic title complex, namely, tetra-bromido-tetra-μ-hydroxido-hexa-kis-[μ-2-methyl-3-(pyrrolidin-1-yl)propan-2-olato]hexa-zinc(II) acetone disolvate, [Zn6Br4(C9H18NO)4(OH)4]·2C3H6O2, is generated by a crystallographic centre of symmetry. Two of the unique zinc atoms adopt distorted ZnO2NBr tetra-hedral coordination geometries and the other adopts a ZnO3N tetra-hedral arrangement. Both unique alkoxide ligands are N,O-chelating and both hydroxide ions are μ2 bridging. The crystal structure displays an O-H⋯O hydrogen bond between a μ2-OH group and an acetone solvent mol-ecule. The Hirshfeld surface has been calculated and is described.
