A synthetic
study into the catalytic hydrogen/deuterium (H/D) exchange
of 1° silanes, 2° silanes, and 3° siloxanes is presented,
facilitated by iron-β-diketiminato complexes (
1a
and
1b
). Near-complete H/D exchange is observed for
a variety of aryl- and alkyl-containing hydrosilanes and hydrosiloxanes.
The reaction tolerates alternative hydride source pinacolborane (HBpin),
with quantitative H/D exchange. A synthetic and density functional
theory (DFT) investigation suggests that a monomeric iron-deuteride
is responsible for the H/D exchange.
While polymers containing chain or ring motifs in their
backbone
are ubiquitous, those containing well-defined molecular cages are
very rare and essentially unknown for the inorganic elements. We report
that a rigid and dinucleophilic cage (PNSiMe3)2(NMe)6, which is chemically robust and accessible on a
multi-gram scale from commercial precursors, serves as a linear and
divalent connector that forms cage-dense inorganic materials. Reaction
of the cage with various ditopic P(III) dihalide comonomers proceeded
via Me3SiCl elimination to give high molecular weight (30 000–70 000
g mol–1), solution-processable polymers that form
free-standing films. The end groups of the polymers could be tuned
to engender orthogonal reactivity and form block copolymers. Networked
cage-dense materials could be accessed by using PCl3 as
a tritopic P(III) linker. Detailed mechanistic studies implicate a
stepwise polycondensation that proceeds via phosphino–phosphonium
ion intermediates, prior to Me3SiCl loss. Thus, metathesis
between the dinucleophilic cage and polyhalides represents a general
strategy to making cage-dense polymers, setting the stage for systematically
understanding the consequences of the three-dimensional microstructure
on macroscopic material properties.
Reduction of carbon-carbon double bonds is reported using a three-coordinate iron(II) β-diketiminate pre-catalyst. The reaction is believed to proceed via a formal transfer hydrogenation using poly(methylhydrosiloxane), PMHS, as the hydride...
Herein, we report the B(C 6 F 5 ) 3 -catalyzed E-selective isomerization of alkenes. The transition-metal-free method is applicable across a diverse array of readily accessible substrates, giving access to a broad range of synthetically useful products containing versatile stereodefined internal alkenes. The reaction mechanism was investigated by using synthetic and computational methods.
A rare study into the catalytic hydrophosphination of allenes is reported. Employing an Fe(II) ß-diketiminate pre-catalyst, the reaction of HPPh2 proceeds with a range of aryl- and alkyl allenes. For arylallenes the E-vinyl product formed as the major species, while the 1,1-disubstituted alkene is formed in a larger ratio than the Z-vinyl product (e.g. 6 : 3 : 1 as E : 1,1 : Z). Use of H2PPh results in good yields of the 1,1-disubstituted alkene, where the resultant secondary phosphine product does not undergo further reaction. We postulate a catalytic cycle based on spectroscopic data. Employing an [Fe(salen)]2-μ-oxo pre-catalyst leads to phosphine dehydrocoupling rather than hydrophosphination.
Correction for ‘Room temperature iron catalyzed transfer hydrogenation using n-butanol and poly(methylhydrosiloxane)’ by Thomas G. Linford-Wood et al., Green Chem., 2021, 23, 2703–2709, DOI: 10.1039/D0GC04175K.
Ruthenium complexes of hemilabile phosphinocarboxamide ligands, and their use to form metallacycles using halide abstraction/deprotonation reactions are reported. Thus, [Ru(p-cym){PPh2C(=O)NHR}Cl2; R = iPr (1), Ph (2), p-tol (3)] and [Ru(p-cym){PPh2C(=O)N(R)C(=O)N(H)R}Cl2; R = Ph (4), p-tol (5)] were synthesized from [(p-cym)RuCl2]2 (p-cym = para-cymene) and phosphinocarboxamides or phosphinodicarboxamides, respectively. Single crystal X-ray diffraction measurements on 1–5 reveal coordination to ruthenium through the phosphorus donor, with an intramolecular hydrogen bond between the amine-bound proton and a metal-bound chloride. Six-membered metallacycles formed by halide abstraction/deprotonation of complexes 4 and 5 afforded [Ru(p-cym){κ2-P,N-PPh2C(=O)N(R)C(=O)NR}Cl] [R = Ph (6), p-tol (7)]. These species exist as a mixture of two rotational isomers in solution, as demonstrated by NMR spectroscopy.
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