Influence of the Steric Demand of the 2,4,6-Trialkylphenyl Substituents on the Structures and Reactivity of Diarylzinc

Structural and Electronic Studies of Substituted m-Terphenyl Group 12 Complexes

The effects of para-substitution on the structural and electronic properties of four series of two-coordinate m-terphenyl Group 12 complexes (R-Ar^#)₂M (M = Zn, Cd, Hg; R = t-Bu 1–3, SiMe₃4–6, Cl 7–9, CF₃10–12, where R-Ar^# = 2,6-{2,6-Xyl}₂-4-R-C₆H₂ and 2,6-Xyl = 2,6-Me₂C₆H₃) have been investigated. X-ray crystallography shows little structural variation across the series, with no significant change in the C–M–C bond distances and angles. However, considerable electronic differences are revealed by heteronuclear nuclear magnetic resonance (NMR) spectroscopy; a linear correlation is observed between the ¹¹³Cd, ¹⁹⁹Hg, and ¹H (2,6-Xyl methyl protons) NMR chemical shifts of the para-substituted complexes and the Hammett constants for the R-substituents. Specifically, an upfield shift in the NMR signal is observed with increasingly electron-withdrawing R-substituents. Density functional theory (DFT) calculations are employed to attempt to rationalize these trends.

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

As a synthesis technique, halide metathesis (n RM + M'X_n → R_nM' + n MX) normally relies for its effectiveness on the favorable formation of a metal halide byproduct (MX), often aided by solubility equilibria in solution. Owing to the lack of significant thermodynamic driving forces, intra-alkali metal exchange is one of the most challenging metathetical exchanges to attempt, especially when conducted without solvent. Nevertheless, grinding together the bulky potassium allyl [KA']_∞ (A' = [1,3-(SiMe₃)₂C₃H₃]^–) and CsI produces the heterometallic complex [CsKA'₂]_∞ in low yield, which was crystallographically characterized as a coordination polymer that displays site disorder of the K⁺ and Cs⁺ ions. The entropic benefits of mixed Cs/K metal centers, but more importantly, the generation of multiple intermolecular K^…CH₃ and Cs^…CH₃ interactions in [CsKA'₂]_∞, enable an otherwise unfavorable halide metathesis to proceed with mechanochemical assistance. From this result, we demonstrate that ball milling and unexpected solid-state effects can permit seemingly unfavored reactions to occur.

Ligand influences on homoleptic Group 12 m-terphenyl complexes

The analysis of three series of two-coordinate Group 12 bis-terphenyl complexes highlights how subtle changes to ligand properties, particularly sterics, and, to a smaller extent, electronics have a large effect on the solid state structures adopted.

Bis(2,4,6-trimethyl-phen-yl)zinc(II)

The title compound, [Zn(C(9)H(11))(2)] or Mes(2)Zn (Mes = mesityl = 2,4,6-trimethyl-phen-yl), crystallizes with a quarter of a mol-ecule in the asymmetric unit. The Zn(II) atom is in a strictly linear environment with a Zn-C bond length of 1.951 (5) Å. Due to the imposed 2/m symmetry, both aromatic rings are coplanar. One of the methyl groups is disordered over two equally occupied positions.