Issue 26, 2019

Mono, bis, and tris(phosphoramidate) titanium complexes: synthesis, structure, and reactivity investigations

Abstract

A series of variously substituted phosphoramidate titanium complexes bearing dimethylamido ligands are reported. Aryl-substituted ligands impart crystallinity to the systems and allow for the elucidation of the molecular structures via X-ray crystallography. Higher-substituted complexes, including a tris(phosphoramidate)mono(dimethylamido) complex, were isolated and characterized in the solid state, as well as in solution using variable temperature 1H and 31P NMR spectroscopy. The steric bulk possessed by this ligand system, relative to amidate and ureate ligands, has allowed access to a mono(phosphoramidate)tris(dimethylamido) complex. The first solid-state-molecular structure of a mono-ligated 1,3-N,O chelated complex of titanium is reported and compared to the respective bis- and tris-analogues. These complexes were screened for hydroaminoalkylation activity between secondary amines and terminal alkenes and the intramolecular hydroamination of a terminal aminoalkene. Mono(phosphoramidate)tris(dimethylamido) complexes were screened in situ and found to be more active than their respective bis(N,O)-chelated analogues. The elucidation of these complexes allows for a direct comparison to other N,O-chelates of early transition metals, particularly in their hydroaminoalkylation and hydroamination reactivity.

Graphical abstract: Mono, bis, and tris(phosphoramidate) titanium complexes: synthesis, structure, and reactivity investigations

Supplementary files

Article information

Article type
Paper
Submitted
28 feb 2019
Accepted
22 apr 2019
First published
09 mei 2019

Dalton Trans., 2019,48, 9782-9790

Mono, bis, and tris(phosphoramidate) titanium complexes: synthesis, structure, and reactivity investigations

M. R. Perry, D. J. Gilmour and L. L. Schafer, Dalton Trans., 2019, 48, 9782 DOI: 10.1039/C9DT00911F

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