Catalytic bond forming reactions promoted by amidinate, guanidinate and phosphaguanidinate compounds of magnesium

Abstract

The synthesis and catalytic properties of a series of magnesium compounds consisting of monoanionic, N,N'-chelating ligands (N∩N = amidinates, guanidinates, phosphaguanidinates) is reported. The compounds were synthesized by (i) insertion of a carbodiimide into an existing Mg-C or Mg-N bond, or (ii) protonolysis of an organomagnesium compound by a neutral pre-ligand. Structural analyses of mono- or bis-(chelate) compounds with general formula Mg(N∩N)X(L)n and Mg(N∩N)2(L)n (X = halide, aryloxide, amide; L = Et2O, THF; n = 0, 1 or 2) have been performed and the influence that the ligand substituent patterns have on the solid-state structures has been probed. Selected examples of the compounds were tested as (pre)catalysts for the polymerization of lactide, the dimerization of aldehydes and the hydroacetylenation of carbodiimides.

Magnesium hydrides bearing sterically demanding amidinate ligands: synthesis, reactivity and catalytic application

“…Coles and co-workers have previously shown related magnesium amides and alkoxides to be efficient catalysts for the Tishchenko reaction, but this is the first example of a magnesium hydride compound being used as a precatalyst. 28,29 Compound 1b was also found to be catalytically active towards the dimerization of benzaldehyde, with only trace amounts of starting material remaining after 10 minutes under the same reaction conditions which is significantly faster than the previously reported magnesium amides (95% yield after 3 h). Interestingly, upon addition of benzaldehyde to 1b, the solution remained colourless, suggesting both 1b and 3b proceed via different catalytic intermediates.…”

Magnesium Catalysis for the Hydroboration of Carbodiimides

“…Although the application of heavier Group 2 (Ca, Sr and Ba) derivatives in molecular catalysis has advanced rapidly during the last decade, an even broader palette of reactivity is now provided by their lighter congener, magnesium . The magnesium‐catalysed addition of terminal acetylenes to carbodiimides, for example, allows access to a variety of propargylamidine small molecules, through a catalytic manifold derived from the sequence of E−H protonolysis and heterocumulene insertion steps shown in the Scheme (a). In such cases, entry to the catalytic cycle, the regiochemistry of the final product and the formation of the new C−C bond are dictated by the protic nature of the C−H bonded terminal acetylene substrate.…”

Role of Alkaline-Earth Metal-Catalyst: A Theoretical Study of Pyridines Hydroboration

“…In the past few decades, many research groups have prepared series of organic Ae metal compounds, which have wide application prospects owing to their low cost and toxicity (Arrowsmith et al, 2011; Liu et al, 2012; Intemann et al, 2014; Schwamm et al, 2014; Hill et al, 2016; Rossin and Peruzzini, 2016). One of the most important applications is the hydrogen transfer reaction, in which Ae metal hydrides are usually used to transfer hydrogen atoms and they show unique catalytic activity (Dunne et al, 2011; Harder et al, 2011; Praneeth et al, 2012; Intemann et al, 2013; Liptrot et al, 2014; Anker et al, 2015; Weetman et al, 2016).…”