10.1021/acs.organomet.7b00871.s001
Benjamin Freitag
Benjamin
Freitag
Jürgen Pahl
Jürgen
Pahl
Christian Färber
Christian
Färber
Sjoerd Harder
Sjoerd
Harder
Syntheses of Heteroleptic Amidinate Strontium Complexes
Using a Superbulky Ligand
American Chemical Society
2018
ligand
TolAm
PhSiH 3
t BuAm DIPP
t BuAm DIPP SrH
Superbulky Ligand Strontium complexes
amidine t BuAm DIPP
SrN
intramolecular alkene hydroamination
deprotonated Ph 2 CH substituent
NMR
Heteroleptic Amidinate Strontium Complexes
latter
Ph 2 CH substituent
Ar
2018-01-22 14:19:32
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Syntheses_of_Heteroleptic_Amidinate_Strontium_Complexes_Using_a_Superbulky_Ligand/5809671
Strontium
complexes are presented with two different bulky amidinate
ligands (Am): <i>t</i>BuC(N<i>-</i>DIPP)<sub>2</sub> (DIPP = 2,6-diisopropylphenyl), abbreviated here as <i>t</i>BuAm<sup>DIPP</sup>, and (<i>p</i>-tolyl)C(N-Ar<sup>‡</sup>)<sub>2</sub> (Ar<sup>‡</sup> = 2,6-Ph<sub>2</sub>CH-4-<i>i</i>Pr-phenyl) abbreviated here as <i>p</i>TolAm<sup>Ar‡</sup>. The amidine <i>t</i>BuAm<sup>DIPP</sup>-H was deprotonated by Sr[N(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> in benzene at 60 °C. Although the product, <i>t</i>BuAm<sup>DIPP</sup>SrN(SiMe<sub>3</sub>)<sub>2</sub>, could be characterized
by NMR, attempts to isolate it led to ligand scrambling via a Schlenk
equilibrium. Reaction of in situ prepared <i>t</i>BuAm<sup>DIPP</sup>SrN(SiMe<sub>3</sub>)<sub>2</sub> with PhSiH<sub>3</sub> gave PhH<sub>2</sub>SiN(SiMe<sub>3</sub>)<sub>2</sub> and presumably
the intermediate <i>t</i>BuAm<sup>DIPP</sup>SrH, but the
latter is not stable and the homoleptic complex (<i>t</i>BuAm<sup>DIPP</sup>)<sub>2</sub>Sr was isolated and structurally
characterized. Deprotonation of the bulkier amidine <i>p</i>TolAm<sup>Ar‡</sup>-H with Sr[N(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> needed forcing conditions, inevitably giving rise to
deprotonation of the Ph<sub>2</sub>CH substituent as well. Reaction
of <i>p</i>TolAm<sup>Ar‡</sup>-H with the less bulky
and less basic Sr[N(SiHMe<sub>2</sub>)<sub>2</sub>]<sub>2</sub>, however,
gave the heteroleptic product <i>p</i>TolAm<sup>Ar‡</sup>SrN(SiHMe<sub>2</sub>)<sub>2</sub>, which has been structurally characterized.
The latter was also at 60 °C stable toward ligand scrambling.
Reaction with PhSiH<sub>3</sub> did give hydride exchange, but the
product <i>p</i>TolAm<sup>Ar‡</sup>SrH decomposed
even at −30 °C. Instead, an amidinate complex with a deprotonated
Ph<sub>2</sub>CH substituent was isolated and structurally characterized
(<b>7</b>). The latter catalyzed the intramolecular alkene hydroamination.