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Metal complexes with t-Bu-substituted allyl ligands are relatively rare, especially compared to their conceptually similar trimethylsilyl-substituted analogs. The scarcity partially stems from the few general synthetic entry points for the t-Bu versions. This situation was studied through a modified synthesis for the allyl ligand itself and by forming several mono(allyl)nickel derivatives. After 2,2,6,6-tetramethyl-4-hepten-3-one was converted to the related 5-bromo-2,2,6,6-tetramethylhept-3-ene (A2tBr), a mixture of Ni(COD)2 and A2tBr in the presence of a neutral donor ligand such as MeCN was found to produce the dark red dimeric π-allyl complex [{A2tNiBr}2]. Both NMR and X-ray crystallographic data confirmed that the t-Bu substituents are in a syn, syn-conformation, like that in the previously described [{A′NiBr}2] (A′ = 1,3-(TMS)2C3H3) complex. [{A2tNiBr}2] will form adducts with neutral donors such as PPh3 and IMes (IMes = 1,3-dimesitylimidazol-2-ylidene), but the resulting [A2tNi(PPh3)Br] complex is not as stable as its trimethylsilyl analog. The [A2tNi(IMes)Br] complex crystallizes from hexanes as a monomer, with an η3-coordinated [A2t] ligand, and in contrast to the starting arrangement in [{A2tNiBr}2], the t-Bu groups on the A2t ligand are in a syn, anti-relationship. This structure is paralleled in the trimethylsilyl analog [A′Ni(IMes)Br]. DFT calculations were used to compare the structures of t-Bu- and related trimethylsilyl-substituted complexes. 

Owing to the strength of the C–F bond, the ‘direct’ preparation of Grignard reagents, i.e., the interaction of elemental magnesium with an organic halide, typically in an ethereal solvent, fails for bulk magnesium and organofluorine compounds. Previously described mechanochemical methods for preparing Grignard reagents have involved ball milling powdered magnesium with organochlorines or bromines. Activation of the C–F bond through a similar route is also possible, however. For example, milling 1- and 2-fluoronaphthalene with an excess of magnesium metal for 2 h, followed by treatment with FeCl3 and additional milling, produces the corresponding binaphthalenes, albeit in low yields (ca. 20%). The yields are independent of the particular isomer involved and are also comparable to the yields from corresponding the bromonaphthalenes. These results may reflect similar charges that reside on the α-carbon in the naphthalenes, as indicated by density functional theory calculations. 

Ball milling CaI 2 and [KN(SiMe 3 ) 2 ] in a 1 : 1 ratio without solvent, and then extracting the ground material with toluene, yields the synthetically valuable neutral amide [Ca(N(SiMe 3 ) 2 ) 2 ] in good yield, without the contamination by calciate species that complicates solution metathesis routes. The effects on yield of grinding time, milling frequency, and calcium halide identity are also examined. 

Mechanochemistry reveals a novel polymorph of the mercury(II) imidazolate framework, based on square-grid (sql) topology layers. Reaction monitoring and periodic density functional theory calculations show that the sql-structure is of higher stability than the previously reported three-dimensional framework, with the unexpected stabilization of the lower dimensionality structure arising from weak interactions that include short interlayer C-H···Hg contacts, highlighting a potential role for agostic interactions in directing metal-organic framework topology.