5 research outputs found
Reactions of Tungsten Acetylide–Silylene Complexes with Pyridines: Direct Observation of Silylene/Silyl Migration in Tungsten Acetylide and Carbyne/Vinylidene Frameworks
Reaction of acetylide–silylene complex Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>)Â(CC<sup><i>t</i></sup>Bu) (<b>1a</b>) with 4-(dimethylamino)Âpyridine (DMAP) gave an equilibrium
mixture
of DMAP-stabilized silylene acetylide complexes <i>trans-</i> and <i>cis</i>-Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>·DMAP)Â(CC<sup><i>t</i></sup>Bu) (<i><b>trans</b></i><b>-4</b> and <i><b>cis</b></i><b>-4</b>).
The corresponding reaction using Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>)Â(CCSiMe<sub>3</sub>) (<b>2</b>) produced the novel DMAP-coordinated
silenylcarbyne/silylvinylidene complex Cp*Â(CO)<sub>2</sub>WÂ[CCÂ(SiPh<sub>2</sub>·DMAP)Â(SiMe<sub>3</sub>)] (<b>6a</b>) as a major
product, which was equilibrated with <i>trans-</i> and <i>cis</i>-Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>·DMAP)Â(CCSiMe<sub>3</sub>) (<i><b>trans</b></i><b>-5a</b> and <i><b>cis</b></i><b>-5a</b>) via silylene/silyl migration.
The novel structures of <i><b>cis</b></i><b>-4</b> and <b>6a</b> were revealed by X-ray crystallography. A mixture
of <b>2</b> and pyridine exhibited interesting temperature-dependent
NMR spectral changes, indicating the formation of <i>trans-</i> and <i>cis</i>-Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>·py)Â(CCSiMe<sub>3</sub>) (<i><b>trans</b></i><b>-5b</b> and <i><b>cis</b></i><b>-5b</b>) and Cp*Â(CO)<sub>2</sub>WÂ[CCÂ(SiPh<sub>2</sub>·py)Â(SiMe<sub>3</sub>)] (<b>6b</b>) at low temperature, while a mixture of <b>1a</b> and pyridine
showed no such spectral changes
Reactions of Tungsten Acetylide–Silylene Complexes with Pyridines: Direct Observation of Silylene/Silyl Migration in Tungsten Acetylide and Carbyne/Vinylidene Frameworks
Reaction of acetylide–silylene complex Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>)Â(CC<sup><i>t</i></sup>Bu) (<b>1a</b>) with 4-(dimethylamino)Âpyridine (DMAP) gave an equilibrium
mixture
of DMAP-stabilized silylene acetylide complexes <i>trans-</i> and <i>cis</i>-Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>·DMAP)Â(CC<sup><i>t</i></sup>Bu) (<i><b>trans</b></i><b>-4</b> and <i><b>cis</b></i><b>-4</b>).
The corresponding reaction using Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>)Â(CCSiMe<sub>3</sub>) (<b>2</b>) produced the novel DMAP-coordinated
silenylcarbyne/silylvinylidene complex Cp*Â(CO)<sub>2</sub>WÂ[CCÂ(SiPh<sub>2</sub>·DMAP)Â(SiMe<sub>3</sub>)] (<b>6a</b>) as a major
product, which was equilibrated with <i>trans-</i> and <i>cis</i>-Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>·DMAP)Â(CCSiMe<sub>3</sub>) (<i><b>trans</b></i><b>-5a</b> and <i><b>cis</b></i><b>-5a</b>) via silylene/silyl migration.
The novel structures of <i><b>cis</b></i><b>-4</b> and <b>6a</b> were revealed by X-ray crystallography. A mixture
of <b>2</b> and pyridine exhibited interesting temperature-dependent
NMR spectral changes, indicating the formation of <i>trans-</i> and <i>cis</i>-Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>·py)Â(CCSiMe<sub>3</sub>) (<i><b>trans</b></i><b>-5b</b> and <i><b>cis</b></i><b>-5b</b>) and Cp*Â(CO)<sub>2</sub>WÂ[CCÂ(SiPh<sub>2</sub>·py)Â(SiMe<sub>3</sub>)] (<b>6b</b>) at low temperature, while a mixture of <b>1a</b> and pyridine
showed no such spectral changes
Synthesis, Structure, and Reactivity of Tungsten Acetylide–Germylene Complexes
The
novel acetylide–germylene complexes Cp*Â(CO)<sub>2</sub>WÂ(GePh<sub>2</sub>)Â(CCR) (<b>7a</b>, R = SiMe<sub>3</sub>; <b>7b</b>, R = CMe<sub>3</sub>) were synthesized by the reactions of Cp*Â(CO)<sub>2</sub>WÂ(NCMe)ÂMe with Ph<sub>2</sub>HGeCî—¼CR (R = SiMe<sub>3</sub>, CMe<sub>3</sub>). X-ray crystal analysis of <b>7a</b> revealed significantly increased germylene–tungsten and decreased
germylene–acetylide interactions in comparison to the corresponding
interactions in the previously reported acetylide–silylene
complex Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>)Â(CCSiMe<sub>3</sub>)
(<b>1</b>). Complexes <b>7a</b>,<b>b</b> reacted
with acetone to give the six-membered cyclic vinylidene complexes
Cp*Â(CO)<sub>2</sub>Wî—»Cî—»CÂ(R)ÂCMe<sub>2</sub>OGePh<sub>2</sub> (<b>8a</b>, R = SiMe<sub>3</sub>; <b>8b</b>,
R = CMe<sub>3</sub>) by acetone insertion reaction, similar to the
case of <b>1</b> affording Cp*Â(CO)<sub>2</sub>Wî—»Cî—»CÂ(SiMe<sub>3</sub>)ÂCMe<sub>2</sub>OSiPh<sub>2</sub> (<b>2</b>). In the presence of 4-(dimethylamino)Âpyridine (DMAP),
complexes <b>8a</b>,<b>b</b> gave <i>trans</i>- and <i>cis</i>-DMAP-stabilized germylene acetylide
complexes Cp*Â(CO)<sub>2</sub>WÂ(GePh<sub>2</sub>·DMAP)Â(CCR) (<i><b>trans</b></i><b>-</b> and <i><b>cis</b></i><b>-9a</b>, R = SiMe<sub>3</sub>; <i><b>trans</b></i><b>-</b> and <i><b>cis</b></i><b>-9b</b>, R = CMe<sub>3</sub>) and acetone, showing a reactivity
different from that of the silicon analogue <b>2</b>. Complexes <i><b>cis-</b></i><b>9a,b</b> were isolated as crystals
from the reaction of <b>7a,b</b> with DMAP and formed mixtures
with <i><b>trans</b></i><b>-9a,b</b> in solutions, respectively. A mixture of <b><i>cis</i>-</b> and <b><i>trans</i>-9a</b> reacted with acetone to form an equilibrium mixture with <b>8a</b> and DMAP. The reactivity of <b>7a</b>,<b>b</b> toward Me<sub>3</sub>COH was also investigated to
reveal the formation of the vinylidene complexes Cp*Â(CO)<sub>2</sub>WÂ{GePh<sub>2</sub>(OCMe<sub>3</sub>)}î—»Cî—»CHR (<b>10a</b>, R = SiMe<sub>3</sub>; <b>10b</b>, R = CMe<sub>3</sub>); <b>10a</b> is equilibrated with <b>7a</b> and Me<sub>3</sub>COH, whereas <b>10b</b> is further converted to the
carbyne complex Cp*Â(CO)<sub>2</sub>Wî—¼CCHÂ(CMe<sub>3</sub>)Â{GePh<sub>2</sub>(OCMe<sub>3</sub>)} (<b>11</b>)
η<sup>3</sup>‑Silaallyl/Alkenylsilyl Molybdenum Complex: Synthesis, Structure, and Reactivity toward Primary Amines To Form Mo–N–Si Three-Membered Cyclic Complexes
The new η<sup>3</sup>-silaallyl/alkenylsilyl
molybdenum complex
Cp*MoÂ(CO)<sub>2</sub>(η<sup>3</sup>-Ph<sub>2</sub>SiCHCMe<sub>2</sub>) (<b>3</b>) was synthesized by the reaction of Cp*MoÂ(CO)<sub>2</sub>(py)ÂMe with Ph<sub>2</sub>HSiCHî—»CMe<sub>2</sub>. Reactions
of <b>3</b> with primary amines RNH<sub>2</sub> (R = <sup><i>t</i></sup>Bu, <sup><i>i</i></sup>Pr, Et) gave Mo–N–Si
three-membered cyclic complexes Cp*MoÂ(CO)<sub>2</sub>(κ<sup>2</sup>-<i>N</i>,<i>Si</i>-RHNSiPh<sub>2</sub>) (<b>5a</b>, R = <sup><i>t</i></sup>Bu; <b>5b</b>, R = <sup><i>i</i></sup>Pr; <b>5c</b>, R = Et) with
elimination of isobutene. In NMR tube reactions using <sup><i>i</i></sup>PrNH<sub>2</sub> and EtNH<sub>2</sub>, the Mo–N–Si–C
four-membered cyclic complexes Cp*MoÂ(CO)<sub>2</sub>(κ<sup>2</sup>-<i>N</i>,<i>C</i>-RHNSiPh<sub>2</sub>CH<sup><i>i</i></sup>Pr) (<b>4b</b>, R = <sup><i>i</i></sup>Pr; <b>4c</b>, R = Et) were observed as intermediates
leading to <b>5b</b> and <b>5c</b>, respectively. Complex <b>4c</b> was successfully isolated in a preparative reaction. The
molecular structures of <b>3</b>, <b>4c</b>, and <b>5b</b> were determined by X-ray crystal analyses. Interestingly,
the contribution of silylene character was suggested for the SiPh<sub>2</sub> moiety of <b>5b</b> from the X-ray structure. The reaction
of <b>5b</b> with MeOH gave the dinuclear complex Cp*Â(CO)<sub>2</sub>MoÂ(μ-OMe)Â(μ-H)ÂMoÂ(CO)<sub>2</sub>Cp* as a major
product
Synthesis, Structure, and Reactivity of Tungsten Acetylide–Germylene Complexes
The
novel acetylide–germylene complexes Cp*Â(CO)<sub>2</sub>WÂ(GePh<sub>2</sub>)Â(CCR) (<b>7a</b>, R = SiMe<sub>3</sub>; <b>7b</b>, R = CMe<sub>3</sub>) were synthesized by the reactions of Cp*Â(CO)<sub>2</sub>WÂ(NCMe)ÂMe with Ph<sub>2</sub>HGeCî—¼CR (R = SiMe<sub>3</sub>, CMe<sub>3</sub>). X-ray crystal analysis of <b>7a</b> revealed significantly increased germylene–tungsten and decreased
germylene–acetylide interactions in comparison to the corresponding
interactions in the previously reported acetylide–silylene
complex Cp*Â(CO)<sub>2</sub>WÂ(SiPh<sub>2</sub>)Â(CCSiMe<sub>3</sub>)
(<b>1</b>). Complexes <b>7a</b>,<b>b</b> reacted
with acetone to give the six-membered cyclic vinylidene complexes
Cp*Â(CO)<sub>2</sub>Wî—»Cî—»CÂ(R)ÂCMe<sub>2</sub>OGePh<sub>2</sub> (<b>8a</b>, R = SiMe<sub>3</sub>; <b>8b</b>,
R = CMe<sub>3</sub>) by acetone insertion reaction, similar to the
case of <b>1</b> affording Cp*Â(CO)<sub>2</sub>Wî—»Cî—»CÂ(SiMe<sub>3</sub>)ÂCMe<sub>2</sub>OSiPh<sub>2</sub> (<b>2</b>). In the presence of 4-(dimethylamino)Âpyridine (DMAP),
complexes <b>8a</b>,<b>b</b> gave <i>trans</i>- and <i>cis</i>-DMAP-stabilized germylene acetylide
complexes Cp*Â(CO)<sub>2</sub>WÂ(GePh<sub>2</sub>·DMAP)Â(CCR) (<i><b>trans</b></i><b>-</b> and <i><b>cis</b></i><b>-9a</b>, R = SiMe<sub>3</sub>; <i><b>trans</b></i><b>-</b> and <i><b>cis</b></i><b>-9b</b>, R = CMe<sub>3</sub>) and acetone, showing a reactivity
different from that of the silicon analogue <b>2</b>. Complexes <i><b>cis-</b></i><b>9a,b</b> were isolated as crystals
from the reaction of <b>7a,b</b> with DMAP and formed mixtures
with <i><b>trans</b></i><b>-9a,b</b> in solutions, respectively. A mixture of <b><i>cis</i>-</b> and <b><i>trans</i>-9a</b> reacted with acetone to form an equilibrium mixture with <b>8a</b> and DMAP. The reactivity of <b>7a</b>,<b>b</b> toward Me<sub>3</sub>COH was also investigated to
reveal the formation of the vinylidene complexes Cp*Â(CO)<sub>2</sub>WÂ{GePh<sub>2</sub>(OCMe<sub>3</sub>)}î—»Cî—»CHR (<b>10a</b>, R = SiMe<sub>3</sub>; <b>10b</b>, R = CMe<sub>3</sub>); <b>10a</b> is equilibrated with <b>7a</b> and Me<sub>3</sub>COH, whereas <b>10b</b> is further converted to the
carbyne complex Cp*Â(CO)<sub>2</sub>Wî—¼CCHÂ(CMe<sub>3</sub>)Â{GePh<sub>2</sub>(OCMe<sub>3</sub>)} (<b>11</b>)