Ring-Shaped Phosphinoamido-Magnesium-Hydride Complexes: Syntheses, Structures, Reactivity, and Catalysis

Lea Fohlmeister; Andreas Stasch

doi:10.1002/chem.201601623

Ring-Shaped Phosphinoamido-Magnesium-Hydride Complexes: Syntheses, Structures, Reactivity, and Catalysis

Chemistry. 2016 Jul 11;22(29):10235-46. doi: 10.1002/chem.201601623. Epub 2016 Jun 8.

Authors

Lea Fohlmeister¹, Andreas Stasch^{2

3}

Affiliations

¹ School of Chemistry, Monash University, 17 Rainforest Walk, Melbourne, Victoria, 3800, Australia.
² School of Chemistry, Monash University, 17 Rainforest Walk, Melbourne, Victoria, 3800, Australia. as411@st-andrews.ac.uk.
³ School of Chemistry, University of St Andrews, North Haugh, St. Andrews, KY16 9ST, UK. as411@st-andrews.ac.uk.

PMID: 27271460
DOI: 10.1002/chem.201601623

Abstract

A series of magnesium(II) complexes bearing the sterically demanding phosphinoamide ligand, L(-) =Ph2 PNDip(-) , Dip=2,6-diisopropylphenyl, including heteroleptic magnesium alkyl and hydride complexes are described. The ligand geometry enforces various novel ring and cluster geometries for the heteroleptic compounds. We have studied the stoichiometric reactivity of [(LMgH)4 ] towards unsaturated substrates, and investigated catalytic hydroborations and hydrosilylations of ketones and pyridines. We found that hydroborations of two ketones with pinacolborane using various Mg precatalysts is very rapid at room temperature with very low catalyst loadings, and ketone hydrosilylation using phenylsilane is rapid at 70 °C. Our studies point to an insertion/σ-bond metathesis catalytic cycle of an in situ formed "MgH2 " active species.

Keywords: hydrides; hydroboration; hydromagnesiation; hydrosilylation; magnesium.