5 research outputs found
Synthesis of Base-Stabilized Hydrido(hydroborylene)tungsten Complexes and Their Reactions with Terminal Alkynes To Give η<sup>3</sup>‑Boraallyl Complexes
Reaction of the methylÂ(pyridine)Âtungsten
complex Cp*Â(CO)<sub>2</sub>WÂ(py)ÂMe with borane–NHC (NHC = N-heterocyclic
carbene; <sup>Me</sup>IMe, <sup>Me</sup>I<sup><i>i</i></sup>Pr) (<sup>Me</sup>IMe = 1,3,4,5-tetramethylimidazol-2-ylidene, <sup>Me</sup>I<sup><i>i</i></sup>Pr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene)
adducts gave the NHC-stabilized hydridoÂ(hydroborylene)tungsten complexes
Cp*Â(CO)<sub>2</sub>WÂ(H)Â(BH·NHC) (<b>1a</b>: NHC = <sup>Me</sup>IMe, <b>1b</b>: NHC = <sup>Me</sup>I<sup><i>i</i></sup>Pr) as dark brown crystals in high yields accompanied by liberation
of pyridine and methane. X-ray crystal structure analysis revealed
that the W–B bond of <b>1b</b> is bridged by a hydrido
ligand. Reactions of <b>1a</b>,<b>b</b> with phenylacetylene
at room temperature afforded NHC-stabilized η<sup>3</sup>-boraallyl
complexes <b>2a</b>,<b>b</b>, respectively, through a
new type of hydroboration of the alkyne triple bond: i.e., addition
of a hydrogen and a borylene. Reaction of <b>1a</b> with 3-butyn-2-one
also led to hydroboration of the triple bond, not the Cî—»O double
bond, to give η<sup>3</sup>-boraallyl complex <b>3</b>. In the reaction of <b>1a</b> with (trimethylsilyl)Âacetylene,
1-oxo-4-borabutenyl complex <b>4</b> was formed as a primary
product through carboboration of the alkyne triple bond. The subsequent
slow reaction of <b>4</b> at ambient temperature resulted in
the formation of η<sup>3</sup>-boraallyl complex <b>5</b> and carbyne complex <b>6</b> in the ratio of 5:4. In all of
these reactions, regioselective boration of the terminal carbon of
alkynes was observed
Cationic Metallogermylene and Dicationic Dimetallodigermenes: Synthesis by Chloride Abstraction from <i>N</i>‑Heterocyclic Carbene-Stabilized Chlorometallogermylenes
Reaction
of NHC-stabilized dichlorogermylenes (NHC = <i>N</i>-heterocyclic
carbene) with an anionic tungsten complex produced
NHC-stabilized chlorometallogermylenes. Subsequent chloride abstraction
from the products with NaBAr<sub>4</sub> (Ar = 3,5-(CF<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) gave a cationic metallogermylene
or dicationic dimetallodigermenes
Insertion of a Cationic Metallogermylene into E–H Bonds (E = H, B, Si)
A cationic
germylene containing tungsten and N-heterocyclic carbene
units reacted with H<sub>2</sub> in fluorobenzene at 60 °C, resulting
in its insertion into the H–H bond. It also activated the Si–H
bond of ethyldimethylsilane and the B–H bond of pinacolborane
at ambient temperature to give the insertion products. The latter
insertion reactions against hydrosilane and hydroborane were found
to be reversible
Insertion of a Cationic Metallogermylene into E–H Bonds (E = H, B, Si)
A cationic
germylene containing tungsten and N-heterocyclic carbene
units reacted with H<sub>2</sub> in fluorobenzene at 60 °C, resulting
in its insertion into the H–H bond. It also activated the Si–H
bond of ethyldimethylsilane and the B–H bond of pinacolborane
at ambient temperature to give the insertion products. The latter
insertion reactions against hydrosilane and hydroborane were found
to be reversible
Iridium and Platinum Complexes of Li<sup>+</sup>@C<sub>60</sub>
Iridium
and platinum complexes of the lithium cation encapsulated
fullerene Li<sup>+</sup>@C<sub>60</sub> were synthesized and structurally
determined. The encapsulated Li<sup>+</sup> strengthens the π
back-bonding from the transition-metal center to the fullerene cage
and is attracted toward the two negatively charged carbon atoms bound
to the transition metal in the solid state