Synthesis and Characterization of Super Bulky β-Diketiminato Group 1 Metal Complexes

Dafydd D L Jones,Samuel Watts,Cameron Jones

doi:10.3390/inorganics9090072

Abstract

Sterically bulky β-diketiminate (or Nacnac) ligand systems have recently shown the ability to kinetically stabilize highly reactive low-oxidation state main group complexes. Metal halide precursors to such systems can be formed via salt metathesis reactions involving alkali metal complexes of these large ligand frameworks. Herein, we report the synthesis and characterization of lithium and potassium complexes of the super bulky anionic β-diketiminate ligands, known [TCHPNacnac]− and new [TCHP/DipNacnac]− (ArNacnac = [(ArNCMe)2CH]−) (Ar = 2,4,6-tricyclohexylphenyl (TCHP) or 2,6-diisopropylphenyl (Dip)). The reaction of the proteo-ligands, ArNacnacH, with nBuLi give the lithium etherate compounds, [(TCHPNacnac)Li(OEt2)] and [(TCHP/DipNacnac)Li(OEt2)], which were isolated and characterized by multinuclear NMR spectroscopy and X-ray crystallography. The unsolvated potassium salts, [{K(TCHPNacnac)}2] and [{K(TCHP/DipNacnac)}∞], were also synthesized and characterized in solution by NMR spectroscopy. In the solid state, these highly reactive potassium complexes exhibit differing alkali metal coordination modes, depending on the ligand involved. These group 1 complexes have potential as reagents for the transfer of the bulky ligand fragments to metal halides, and for the subsequent stabilization of low-oxidation state metal complexes.

Highlights

The use of sterically demanding β-diketiminate ligand systems for the stabilization of reactive low-oxidation state metal compounds has become commonplace in organometallic chemistry [1,2,3,4,5,6,7,8]
A successful use of β-diketiminates has been the stabilization of magnesium(I) dimers, e.g., LMg–MgL
Attempts to increase the steric profile of β-diketiminate ligands, in the hope that compounds elusive to stabilization by the

Summary

Introduction

The use of sterically demanding β-diketiminate ligand systems for the stabilization of reactive low-oxidation state metal compounds has become commonplace in organometallic chemistry [1,2,3,4,5,6,7,8]. This has seen widespread use due to its ease of synthesis from commercially available starting materials and the high kinetic stabilization it imparts to the coordinated metal. Dip Nacnac system can be isolated, are worthwhile pursuits, with notable successes coming from the groups of Piers [13], Holland [14] and Hill [15]. With respect to the stabilization of group 2 compounds, bulky β-diketiminate ligands based on 2,6-bis(diphenylmethyl)-aryl

Methods

Results

Conclusion