N-(Mesityl)-oxanilic acid ethyl ester (1, Ar = Mesityl). 2,4,6-Trimethylaniline (20 mL, 142 mmol, 1.0 equiv.) and triethylamine (20 mL, 143 mmol, 1 equiv.) were dissolved in dry THF (150 mL). This solution was cooled to 0 °C, and ethyl chlorooxoactetate (15.3 mL, 142 mmol, 1.0 equiv.) was added slowly via syringe. Precipitation of a white solid occurred immediately upon addition. It was allowed to stir overnight, warming to room temperature. At this point, the solid was filtered off, and the organic layer was washed with 2 M HCl solution (2x100 mL). The aqueous layer was washed with ethyl acetate, and the combined organic layers were washed with brine (100 mL), and dried over MgSO 4. The solvent was then removed under reduced pressure, leaving a yellowish solid. This was recrystallized from hexanes/EtOAc (9:1), producing a white crystalline solid (30.15 g, 128 mmol, 90% yield).

A facile synthesis of nickel salicylaldimine complexes with labile dissociating ligands is described. In addition to producing highly active ethylene polymerization catalysts, important insights into the effect of ligand size on catalyst stability and information on the mechanism of polymerization are provided.

Materials and Methods.All reactions involving metal complexes were conducted in oven-dried glassware under a nitrogen atmosphere using standard glovebox techniques. Solvents were prepared by passage through alumina. All commercially obtained reagents were used as received. Organic reagents were purchased from Sigma-Aldrich and metal salts obtained from Strem. NiClPh(PPh 3 ) 2 1 and NiBrMes(PPh 3 ) 2 2 were prepared according to literature procedures. The synthesis of compound 1 is described elsewhere. 3 1 H, 13 C and 31 P NMR spectra were recorded on a Varian Mercury 300 spectrometer (at 300 MHz, 75 MHz and 121 MHz respectively) or a Varian Inova 500 spectrometer (at 500 MHz, 125 MHz and 203 MHz respectively) and are reported relative to Me 4 Si (δ 0.0) for 1 H and 13 C, and H 3 PO 4 (δ 0.0) for 31 P. Data for 1 H NMR spectra are reported as follows: chemical shift (δ ppm), multiplicity, coupling constant (Hz) and integration. Data for 13 C and 31 P NMR spectra are reported in terms of chemical shift. N-(2,6-Diisopropylphenyl)-N-benzylidene-N´-(2-hydroxy-3-(adamant-1-yl)-5-methylphenyl)-ethylene diimine triphenylphosphine nickel(II) (2).1-(2,6-Diisopropylphenyl)-3-(2-hydroxy-3-(adamant-1-yl)-5-methylphenyl)-4,5-dihydroimidazolium chloride (1) (162 mg, 0.320 mmol, 1.00 equiv) and potassium hexamethyldisilazide (134 mg, 0.670 mmol, 2.10 equiv) were weighed together in a vial in the glovebox. THF (~10 mL) was added to the mixture of solids, providing a light yellow solution with a light precipitate. This was added to a round-bottomed flask and allowed to stir for ten minutes. At this point, a solution of NiClPh(PPh 3 ) 2 (223 mg, 0.320 mmol, 1.00 equiv) in THF (5 mL) was added, giving a dark green solution with precipitate. This solution was allowed to stir at room temperature for 1 hr and then was filtered through Celite. The solvent was removed under reduced pressure until ca. 2 mL remained. Pentane (~15 mL) was added and the solution was allowed to sit at -40 °C overnight, yielding a dark green solid (163 mg, 0.190 mmol, 59% yield). Crystals suitable for X-ray crystallography were grown by layering pentane over a concentrated solution of 2 in THF and storing this layered solution at -40 °C for two days. The 1 H NMR spectrum of 2 showed some broad peaks attributed to a fluxional process on the NMR timescale. This is most likely due to restricted rotation of the diisopropylphenyl and phenyl moieties, which are adjacent in the X-ray crystallographic structure. The 13 C NMR spectrum of 2 features many fewer resonances than expected. This may be due to the fact that several resonances may overlap, e.g. from the triphenylphosphine and adamantyl moieties. In addition, the fluxional processes described above may weaken some signals. 1

Trick or treat? Ruthenium alkylidene catalyzed ring‐closing metathesis of crown ether like diene substrates around a dumbbell‐shaped secondary ammonium ion affords [2]rotaxanes. The reversible nature of this process has been demonstrated through a “magic ring” synthesis, wherein the preformed olefinic macrocycle and dumbbell‐shaped component equilibrate to form the hydrogen‐bond‐stabilized [2]rotaxane in the presence of a metathesis catalyst (see scheme).

Materials and Methods. All reactions were set up in a nitrogen glovebox. Methyl acrylate, and allylbenzene were purchased from the Sigma-Aldrich Chemical Company, Milwaukee, WI. They were dried over CaH 2 and distilled under reduced pressure. Methyl acrylate 2,3,3-d 3 and toluene-d 8 were purchased from Cambridge Isotope Laboratories, Inc., Andover, MA. Methyl acrylate 2,3,3-d 3 was used as received. Toluene-d 8 was dried over Na 0 /benzophenone and distilled under reduced pressure. The synthesis of compound 1 is described elsewhere.1 1 H spectra were recorded on a Varian Mercury 300 spectrometer (at 300 MHz). GC-MS data were obtained on an HP 5890 GC with an Agilent DB-5MS+DG column, and an HP 5970 EI mass selective detector. The GC was operated with the following oven program: begin at 70 °C, heat to 270 °C at a rate of 15 °C/min., maintain for 5 min., return to 70 °C at a rate of 50 °C/min. The GC traces of methyl cinnamate (2) and methyl 3-phenylpropionate (3) were confirmed by comparison with authentic samples, obtained from Sigma-Aldrich and Lancaster Synthesis, Pelham, NH, respectively. The identities of methyl phenylacrylate 2 and methyl 2-phenylpropionate 3 were confirmed by independent synthesis. The identities of the products of reaction between 1 and allylbenzene (six isomers of 1,3-diphenylpropylene and two isomers of 1,3-diphenylpropane) were confirmed by their mass spectra in the GC-MS spectrum.4 MALDI/TOF spectra were obtained with an Applied Biosystems Voyager DE PRO with a 20 Hz N 2 laser. The matrix was dithranol (5 mg/mL) in acetonitrile and was used in twofold excess relative to analyte.