Taking Advantage of Hg−C Bonds: Synthesis of the First Homoleptic Bis-β-diketiminate Complex Bound through the γ-Carbons

Abstract

The most common β-diketiminate ligand, [{N(2,6- i Pr2C6H3)C(Me)}2CH]− (BDI), was used to synthesize a new mercury complex in which two BDI ligands are bound to the metal through the γ-carbons in the solid state. In solution, one of the BDI ligands switches to an N,N′-binding mode; this complex is in equilibrium with the homoleptic species. The thermodynamic parameters, ΔH° (−2.52 kcal mol−1), ΔS° (−9.24 cal mol−1 K−1), and ΔG°298 (0.23 kcal mol−1), were measured using variable-temperature 1H NMR spectroscopy.

(β‐Diketiminato)cadmium Bis(trimethylsilyl)amide: Facile Access to Low‐Coordinate Cadmium Complexes

“…An X‐ray diffraction study determined the product to be hydroxide‐bridged dimer [{(BDI)CdOH} 2 ] ( 5 ), isostructural to the Chisholm's zinc dimer [{(BDI)ZnOH} 2 ] (Figure , see Table for data‐collection parameters). [4b] Two different Cd–O bond lengths are observed for hydroxide 5 [2.2359(13) and 2.1936(12) Å], the average (2.215 Å) of which is slightly longer than that reported for the cationic hydroxo‐bridged dimer [{(ebnpa)CdOH} 2 ][ClO 4 ] 2 {average 2.206 Å; ebnpa = N ‐2‐(ethylthio)ethyl‐ N , N ‐bis[(6‐neopentylamino‐2‐pyridyl)methyl]amine} . The longer Cd–O bond corresponds to the endo cadmium–hydroxide bond and the shorter one to the exo cadmium–hydroxide bond, consistent with the exo preference for the more anionic ligand.…”

“…As such, other routes to β‐diketiminato group 12 complexes are required. For instance, synthesis of a three‐coordinate (β‐diketiminato)mercury complex from HgCl 2 is only successful when toluene is used as the solvent, and [Zn(N i Pr 2 ) 2 ] is a common precursor to (β‐diketiminato)zinc complexes …”

On the non-innocence of “Nacnacs”: ligand-based reactivity in β-diketiminate supported coordination compounds

“…Although the negative charge is delocalized on the whole NCCCN ring overall, electron density in the HOMO and HOMO−1 of the BDI ligand is essentially located 10 C κ 1 -(γ-C); 11 D κ 1 -(β-C); 12 E κ 3 -(γ-C,N,N'); 13 F κ 2 -(N,N') and η 3 -(NCC); 14 G κ 2 -(γ-C,N); 15 H η 5 -Ar; 16 I κ 2 -(N,η 6 Ar). Yet, as will be described in the following discussion, tuning BDI steric and electronic properties has a strong impact on the ligand-based reactivity.…”

Zinc, cadmium and mercury

“…For example, it was shown that in the solid-state, homoleptic [Hg(BDI) 2 ] exclusively bonded through the g-carbon (8), although in solution one ligand reverts to the N,N 0 -bonding mode expected for the [BDI] À anion. 53 This is in contrast with the results from a parallel study with zinc and cadmium BDI-complexes, in which conventional N,N 0 -bonding is observed, exclusively. 54 Three independent publications involving the ferrocenyl group as a constituent within a new ligand have been presented.…”