Reversible addition of tin(II) amides to nitriles.

Lappert's stannylene (Sn[N(SiMe3)2]2) has been reacted with various nitriles, dinitriles and trinitriles with the formation of heteroleptic amidotin(II) amidinates of the general formulae [RC(NSiMe3)2]SnN(SiMe3)2, R'{[C(NSiMe3)2]SnN(SiMe3)2}2 and R''{[C(NSiMe3)2]SnN(SiMe3)2}3, where R = Ph (1), 2-(CN)-C6H4 (2), 3-(CN)-C6H4 (3); R' = 1,3-C6H4 (4), 1,4-C6H4 (5) and R'' = 1,3,5-C6H3 (6). The reactions of amidotin(II) benzamidinate 1 with an excess of benzonitrile proceed to homoleptic tin(II) bis(benzamidinate) [PhC(NSiMe3)2]2Sn, which reversibly eliminates benzonitrile and 1 when warmed. The premise of reversibility has been supported by a multinuclear time-dependent NMR study and a theoretical (DFT) description. On the other hand, magnesium(II) bis(benzamidinate) [PhC(NSiMe3)2]2Mg (8) and lanthanum(II) tris(benzamidinate) [PhC(NSiMe3)2]3La (7) have been synthesised from appropriate metal hexamethyldisilazides and benzonitrile.

On the edge of the steric repulsion and reactivity of bulky anilines; a case study of chloro(imino)phosphine synthesis.

2-Benzhydryl-4-methyl-6-(1,1'-diphenyl-2-phenyl-ethyl)aniline was prepared by a three-step process. 2,6-Bis(benzhydryl)-4-methyl-aniline was protected by Schiff coupling, then benzylated and finally dealkylated by using hydrochloric acid and methanol. The resulting compound exhibits one of the highest buried volumes around the nitrogen atom of anilines prepared so far, but it reacts with phosphorus trichloride and triethylamine to give a monomeric chloro(imino)phosphine.

Access to cationic polyhedral carboranes via dynamic cage surgery with N-heterocyclic carbenes.

Polyhedral boranes and heteroboranes appear almost exclusively as neutral or anionic species, while the cationic ones are protonated at exoskeletal heteroatoms or they are instable. Here we report the reactivity of 10-vertex closo-dicarbadecaboranes with one or two equivalents of N-heterocyclic carbene to 10-vertex nido mono- and/or bis-carbene adducts, respectively. These complexes easily undergo a reaction with HCl to give cages of stable and water soluble 10-vertex nido-type cations with protonation in the form of a BHB bridge or 10-vertex closo-type cations containing one carbene ligand when originating from closo-1,10-dicarbadecaborane. The reaction of a 10-vertex nido mono-carbene adduct with phosphorus trichloride gives nido-11-vertex 2-phospha-7,8-dicarbaundecaborane, which undergoes an oxidation of the phosphorus atom to P = O, while the product of a bis-carbene adduct reaction is best described as a distorted C2B6H8 fragment bridged by the (BH)2PCl2+ moiety.

Thiaborane Icosahedral Barrier Increased by the Functionalization of all Terminal Hydrogens in closo-1-SB11H11.

The electrophilic substitution of icosahedral closo-1-SB11H11 with methyl iodide has resulted in two B-functionalized thiaboranes, 7,12-I2-2,3,4,5,6,8,9,10,11-(CH3)9-1-closo-SB11 and 7,8,12-I3-2,3,4,5,6,9,10,11-(CH3)8-closo-1-SB11, with the former being significantly predominant. These two icosahedral thiaboranes are the first cases of polysubstituted polyhedral boron clusters with another vertex that differs from B and C. Such polyfunctionalizations have increased the earlier observed thiaborane icosahedral barrier, not exhibiting any reactivity toward bases, unlike the parent thiaborane. The search for methylation pathways has revealed that the complete B11-methylation is impossible, like in the case of decaborane(14), where this seems to be a result of the positively charged upper parts of these two molecules.

Oxidative addition of cyanogen bromide to C,N-chelated and Lappert's stannylenes.

Stannylenes of L2Sn type bearing either C,N-chelating (1, L = LCN = 2-(N,N-dimethylaminomethyl)phenyl) or bulky amido (2, L = LN = N(SiMe3)2) ligands react with cyanogen bromide (Br-C[triple bond, length as m-dash]N) via an oxidative-addition reaction to give monomeric six-coordinate (LCN)2Sn(Br)CN (1a) and four-coordinate (LN)2Sn(Br)CN (2a) stannanes in moderate yields. In solution, both 1a and 2a undergo instantaneous bromido-cyanido ligand redistribution reactions, leading to mixtures containing 1a, (LCN)2SnBr2 (1b) and (LCN)2Sn(CN)2 (1c) or 2a, (LN)2SnBr2 (2b) and (LN)2Sn(CN)2 (2c), respectively. The prepared species were characterised by multinuclear NMR spectroscopy in solution (1a-c and 2a-c) and in the solid state (1a-c). The crystal structures of 1a/b/c, 2a/b/c and sole 2b were determined by XRD analyses. DFT calculations and QTAIM analysis were also carried out to corroborate the experimental results.

Experimental and Theoretical Evidence of Spin-Orbit Heavy Atom on the Light Atom 1 H†NMR Chemical Shifts Induced through H⋠⋠⋠I- Hydrogen Bond.

Invited for the cover of this issue is the group of Michal Straka and Martin Dracínský (IOCB Prague, Czech Academy of Sciences). The image depicts a neutron star, which is used to represent the relativistic effects between a heavy element and a hydrogen atom reported in this work. Read the full text of the article at 10.1002/chem.202001532.

Experimental and Theoretical Evidence of Spin-Orbit Heavy Atom on the Light Atom 1 H†NMR Chemical Shifts Induced through H⋠⋠⋠I- Hydrogen Bond.

Spin-orbit (SO) heavy-atom on the light-atom (SO-HALA) effect is the largest relativistic effect caused by a heavy atom on its light-atom neighbors, leading, for example, to unexpected NMR chemical shifts of 1 H, 13 C, and 15 N nuclei. In this study, a combined experimental and theoretical evidence for the SO-HALA effect transmitted through hydrogen bond is presented. Solid-state NMR data for a series of 4-dimethylaminopyridine salts containing I- , Br- and Cl- counter ions were obtained experimentally and by theoretical calculations. A comparison of the experimental chemical shifts with those calculated by a standard DFT methodology without the SO contribution to the chemical shifts revealed a remarkable error of the calculated proton chemical shift of a hydrogen atom that is in close contact with the iodide anion. The addition of the relativistic SO correction in the calculations significantly improves overall agreement with the experiment and confirms the propagation of the SO-HALA effect through hydrogen bonds.

The Influence of Halogenated Hypercarbon on Crystal Packing in the Series of 1-Ph-2-X-1,2-dicarba-closo-dodecaboranes (X = F, Cl, Br, I).

Although 1-Ph-2-X-closo-1,2-C2B10H10 (X = F, Cl, Br, I) derivatives had been computed to have positive values of the heat of formation, it was possible to prepare them. The corresponding solid-state structures were computationally analyzed. Electrostatic potential computations indicated the presence of highly positive σ-holes in the case of heavy halogens. Surprisingly, the halogen•••π interaction formed by the Br atom was found to be more favorable than that of I.

Access to the most sterically crowded anilines via non-catalysed C-C coupling reactions.

Variously substituted 2,6-bis(1,1-diarylethyl)anilines and 2,6-bis(trityl)anilines were prepared by a three-step high-yield process. Dimethyl-2-aminoisophtalate was modified by reaction with arylmagnesium bromides, and the hydroxy-derivatives obtained were etherified. Under the non-catalysed C-C coupling protocol, the formed bis[methyl(methoxy)diaryl]anilines react with various Grignard reagents to give highly substituted products. The buried volumes around the central nitrogen atom of the prepared compounds exceed the parameters for the known most sterically hindered anilines by about 20%.

Versatile, one-pot introduction of nonahalogenated 2-ammonio-decaborate ions as boron cluster scaffolds into organic molecules; host-guest complexation with γ-cyclodextrin.

We report the modification of the 2-ammonio group at halogenated decaborate ions with 2,3-epoxypropane, the product of which reacts readily with nucleophiles to form previously inaccessible coupling of polyhedra with organic molecules and materials. We demonstrate that these ions present a good binding motif in supramolecular chemistry.

Thiaborane clusters with an exoskeletal B-H group.

The thiaboranes closo-1-SB11H11 (1a) and 12-I-closo-1-SB11H10 (1b) react with 4-(dimethylamino)pyridine under inert conditions upon the formation of the nido-type thiaboranes 9-B{(4-Me2N)C5NH4}2(H)-7-SB10H11 and 9-B{(4-Me2N)C5NH4}2(H)-5-I-7-SB10H10 containing an exoskeletal B-H group. The same type of B-H moiety is also stabilised by one bipyridine molecule in a chelating fashion. These complexes are unstable in solution, and in air and hydrolyse to monodeboronated ionic compounds having [nido-7-SB10H11]- or [5-I-nido-7-SB10H10]- anions which are also products of the reactions of 1a and 1b with other N-bases such as pyridine, ammonia and DABCO. The extrusion of one boron and one sulphur atom takes place when 1a reacts with 2,6-di-tert-butylpyridine to yield decaborane.