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The Pd‐catalyzed intramolecular allylic alkylation of unsaturated amides to give γ‐ and δ‐lactams has been studied in the presence of chiral ligands. Ligand (R)‐3,5‐tBu‐MeOBIPHEP (MeOBIPHEP=6,6’‐dimethoxybiphenyl‐2,2‐diyl)bis(diphenylphosphine)) afforded the best results and allowed the cyclization reactions to take place in up to 94:6 enantiomeric ratio. A model Pd–allyl complex has been prepared and studied through NMR spectroscopic analysis, which provided insight into the processes responsible for the observed enantiomeric ratios. DFT studies were used to characterize the diastereomeric reaction pathways. The calculated energy differences were in good agreement with the experimentally observed enantiomeric ratios.

The five‐coordinate ruthenium N‐heterocyclic carbene (NHC) hydrido complexes [Ru(IiPr2Me2)4H][BArF4] (1; IiPr2Me2=1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene; ArF=3,5‐(CF3)2C6H3), [Ru(IEt2Me2)4H][BArF4] (2; IEt2Me2=1,3‐diethyl‐4,5‐dimethylimidazol‐2‐ylidene) and [Ru(IMe4)4H][BArF4] (3; IMe4=1,3,4,5‐tetramethylimidazol‐2‐ylidene) have been synthesised following reaction of [Ru(PPh3)3HCl] with 4–8 equivalents of the free carbenes at ambient temperature. Complexes 1–3have been structurally characterised and show square pyramidal geometries with apical hydride ligands. In both dichloromethane or pyridine solution, 1and 2display very low frequency hydride signals at about δ−41. The tetramethyl carbene complex 3exhibits a similar chemical shift in toluene, but shows a higher frequency signal in acetonitrile arising from the solvent adduct [Ru(IMe4)4(MeCN)H][BArF4], 4. The reactivity of 1–3towards H2and N2depends on the size of the N‐substituent of the NHC ligand. Thus, 1is unreactive towards both gases, 2reacts with both H2and N2only at low temperature and incompletely, while 3affords [Ru(IMe4)4(η2‐H2)H][BArF4] (7) and [Ru(IMe4)4(N2)H][BArF4] (8) in quantitative yield at room temperature. CO shows no selectivity, reacting with 1–3to give [Ru(NHC)4(CO)H][BArF4] (9–11). Addition of O2to solutions of 2and 3leads to rapid oxidation, from which the RuIIIspecies [Ru(NHC)4(OH)2][BArF4] and the RuIVoxo chlorido complex [Ru(IEt2Me2)4(O)Cl][BArF4] were isolated. DFT calculations reproduce the greater ability of 3to bind small molecules and show relative binding strengths that follow the trend CO ≫ O2> N2> H2.

Pulsed gradient spin‐echo (PGSE) diffusion characteristics for a) the new [brucinium][X] salts 6 a–f[a: X=BF4−; b: X=PF6−; c: X=MeSO3−, d: X=CF3SO3−; e: X=BArF−; f: X=PtCl3(C2H4)−], b) 4‐tert‐butyl‐N‐benzyl analogue, 7and c) the aryl carbocations (p‐R‐C6H4)2CH 9 a(R=CH3O) and 9 b(R=(CH3)2N), (p‐CH3O‐C6H4)xCPh3−x+10 a–c(x=1–3, respectively) and (p‐R‐C6H4)3C+11(R=(CH3)2N) and 12(R=H) all in several different solvents, are reported. The solvent dependence suggests strong ion pairing in CDCl3, intermediate ion pairing in CD2Cl2and little ion pairing in [D6]acetone. 1H, 19F HOESY NMR spectra (HOESY: heteronuclear Overhauser effect spectroscopy) for 6and 7reveal a specific approach of the anion with respect to the brucinium cation plus subtle changes, which are related to the anion itself. Further, for carbocations 9–12, (all as BF4−salts) based on the NOE results, one finds marked changes in the relative positions of the BF4−anion. In these aryl cationic species the anion can be located either a) very close to the carbonium ion carbon b) in an intermediate position or c) proximate to the N or O atom of the p‐substituent and remote from the formally positive C atom. This represents the first example of such a positional dependence of an anion on the structure of the carbocation. DFT calculations support the experimental HOESY results. The solid‐state structures for 6 cand the novel Zeise's salt derivative, [brucinium][PtCl3(C2H4)], 6 f, are reported. Analysis of 195Pt NMR and other NMR measurements suggest that the η2‐C2H4bonding to the platinum centre in 6 fis very similar to that found in K[PtCl3(C2H4)]. Field dependent T1measurements on [brucinium][PtCl3(C2H4)] and K[PtCl3(C2H4)], are reported and suggested to be useful in recognizing aggregation effects.

Green and fast: Allylation of aromatic and aliphatic thiols, by using allyl alcohols as substrates, requires only minutes at ambient temperature with a Ru catalyst (see scheme). Quantitative conversion is normal and the catalyst possesses high functional‐group tolerance.

PGSE diffusion, 19F, 1H HOESY and 13C NMR studies for a series of [Ru(Cp*)(η6‐arene)][PF6] (1) salts are presented. The solid‐state structure of [Ru(Cp*)(η6‐fluorobenzene)][PF6] (1 c) is reported. The extent of the ion pairing and the relative positions of the ions are shown to depend on the arene. For the solvent dichloromethane, new and literature PGSE data for PF6−salts of transition‐metal, inorganic, and organic salts are compared. Taken together, these new results show that the charge distribution and the ability of the anion to approach the positively charged positions (steric effects due to molecular shape) are the determining factors in deciding the amount of ion pairing. DFT calculations of the charges in four salts of type 1, as well as in a variety of other salts, using a natural population analysis (NPA), support this view. This represents the first attempt, using experimental data, to understand, correlate, and partially explain the various degrees of ion pairing in a widely different collection of salts.

In non‐competitive solvents, the tris(3‐ureidobenzyl)amines 1 a–cform dimeric assemblies in which guests such as CH3CN, CH3NO2, CH2Cl2, CH3I, CH2BrCl, CH2Br2, CHCl3and C6H6can be encapsulated. Variable temperature 1H and 1H,1H‐ROESY NMR spectroscopy, as well as pulsed‐gradient spin‐echo (PGSE) diffusion measurements were used to investigate the encapsulation within 1 a⋅1 a(1 a: tris{3‐[N′‐(4‐butylphenyl)ureido]benzyl}amine). Kinetic parameters for the encapsulation of CH3NO2, CH2Cl2and CH3I, both in CDCl3and in [D8]toluene have been obtained by using magnetisation transfer methods. These data are discussed together with the thermodynamic parameters. The affinity between guest and capsule seems to be dictated mainly by the electronic, size and shape complementarity between cavity and guest. A gating mechanism for guest exchange is proposed.

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Compounds formed by linking two tris(ureidobenzyl)amine modules with a hexamethylene tether are described. These compounds self‐assemble to form bicapsular aggregates featuring two rings of six hydrogen‐bonded ureas. 1H and 1H/1H ROESY NMR spectroscopy, together with pulsed gradient spin echo (PGSE) NMR diffusion measurements, have been used to characterize the dimers in solution. The results have been compared with energy‐minimized structures. The new compounds are kinetically stable on the NMR timescale, and their thermodynamic stabilities are comparable to other capsular aggregates derived from tris(ureidobenzyl)amines.

PGSE NMR diffusion, Overhauser and DFT studies on the salts [Pd(η³-CH3CHCHCHPh)(dppe)](anion) (dppe = 1,2-bis(diphenylphosphino)ethane, anion = BF4^-, CF3SO3^-, BArF^-, PF6^-) are reported. In dichloromethane solution there is little or no ion pairing for the BArF derivative, whereas the other three anions show intermediate degrees of ion pairing. In chloroform solution the CF3SO3^- and BArF^- salts show complete ion pairing. The ¹⁹F,¹H HOESY studies reveal a selective approach of the CF3SO3^- and PF6^- anions with respect to the allyl ligand. The approach brings the anion somewhat closer to the allyl phenyl ring than to the allyl methyl group. Further, the anion approaches the Pd center from the side of the two terminal allyl protons. The anions are not attracted to the allyl ligand but rather are choosing both an electronically (allyl phenyl vs allyl methyl) and sterically (terminal allyl protons vs central allyl proton) preferred pathway toward the P and metal atoms. This result is partially rationalized via DFT calculations.