Synthesis, Structure, and Reactivity of Tungsten Acetylide–Germylene Complexes

The novel acetylide–germylene complexes Cp*­(CO)₂W­(GePh₂)­(CCR) (<b>7a</b>, R = SiMe₃; <b>7b</b>, R = CMe₃) were synthesized by the reactions of Cp*­(CO)₂W­(NCMe)­Me with Ph₂HGeCCR (R = SiMe₃, CMe₃). 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*­(CO)₂W­(SiPh₂)­(CCSiMe₃) (<b>1</b>). Complexes <b>7a</b>,<b>b</b> reacted with acetone to give the six-membered cyclic vinylidene complexes Cp*­(CO)₂WCC­(R)­CMe₂OGePh₂ (<b>8a</b>, R = SiMe₃; <b>8b</b>, R = CMe₃) by acetone insertion reaction, similar to the case of <b>1</b> affording Cp*­(CO)₂WCC­(SiMe₃)­CMe₂OSiPh₂ (<b>2</b>). In the presence of 4-(dimethylamino)­pyridine (DMAP), complexes <b>8a</b>,<b>b</b> gave <i>trans</i>- and <i>cis</i>-DMAP-stabilized germylene acetylide complexes Cp*­(CO)₂W­(GePh₂·DMAP)­(CCR) (<i><b>trans</b></i><b>-</b> and <i><b>cis</b></i><b>-9a</b>, R = SiMe₃; <i><b>trans</b></i><b>-</b> and <i><b>cis</b></i><b>-9b</b>, R = CMe₃) 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 Me₃COH was also investigated to reveal the formation of the vinylidene complexes Cp*­(CO)₂W­{GePh₂(OCMe₃)}CCHR (<b>10a</b>, R = SiMe₃; <b>10b</b>, R = CMe₃); <b>10a</b> is equilibrated with <b>7a</b> and Me₃COH, whereas <b>10b</b> is further converted to the carbyne complex Cp*­(CO)₂WCCH­(CMe₃)­{GePh₂(OCMe₃)} (<b>11</b>)

Synthesis, Structure, and Reactivity of Tungsten Acetylide–Germylene Complexes

The novel acetylide–germylene complexes Cp*­(CO)₂W­(GePh₂)­(CCR) (<b>7a</b>, R = SiMe₃; <b>7b</b>, R = CMe₃) were synthesized by the reactions of Cp*­(CO)₂W­(NCMe)­Me with Ph₂HGeCCR (R = SiMe₃, CMe₃). 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*­(CO)₂W­(SiPh₂)­(CCSiMe₃) (<b>1</b>). Complexes <b>7a</b>,<b>b</b> reacted with acetone to give the six-membered cyclic vinylidene complexes Cp*­(CO)₂WCC­(R)­CMe₂OGePh₂ (<b>8a</b>, R = SiMe₃; <b>8b</b>, R = CMe₃) by acetone insertion reaction, similar to the case of <b>1</b> affording Cp*­(CO)₂WCC­(SiMe₃)­CMe₂OSiPh₂ (<b>2</b>). In the presence of 4-(dimethylamino)­pyridine (DMAP), complexes <b>8a</b>,<b>b</b> gave <i>trans</i>- and <i>cis</i>-DMAP-stabilized germylene acetylide complexes Cp*­(CO)₂W­(GePh₂·DMAP)­(CCR) (<i><b>trans</b></i><b>-</b> and <i><b>cis</b></i><b>-9a</b>, R = SiMe₃; <i><b>trans</b></i><b>-</b> and <i><b>cis</b></i><b>-9b</b>, R = CMe₃) 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 Me₃COH was also investigated to reveal the formation of the vinylidene complexes Cp*­(CO)₂W­{GePh₂(OCMe₃)}CCHR (<b>10a</b>, R = SiMe₃; <b>10b</b>, R = CMe₃); <b>10a</b> is equilibrated with <b>7a</b> and Me₃COH, whereas <b>10b</b> is further converted to the carbyne complex Cp*­(CO)₂WCCH­(CMe₃)­{GePh₂(OCMe₃)} (<b>11</b>)

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*­(CO)₂W­(SiPh₂)­(CC^<i>t</i>Bu) (<b>1a</b>) with 4-(dimethylamino)­pyridine (DMAP) gave an equilibrium mixture of DMAP-stabilized silylene acetylide complexes <i>trans-</i> and <i>cis</i>-Cp*­(CO)₂W­(SiPh₂·DMAP)­(CC^<i>t</i>Bu) (<i><b>trans</b></i><b>-4</b> and <i><b>cis</b></i><b>-4</b>). The corresponding reaction using Cp*­(CO)₂W­(SiPh₂)­(CCSiMe₃) (<b>2</b>) produced the novel DMAP-coordinated silenylcarbyne/silylvinylidene complex Cp*­(CO)₂W­[CC­(SiPh₂·DMAP)­(SiMe₃)] (<b>6a</b>) as a major product, which was equilibrated with <i>trans-</i> and <i>cis</i>-Cp*­(CO)₂W­(SiPh₂·DMAP)­(CCSiMe₃) (<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*­(CO)₂W­(SiPh₂·py)­(CCSiMe₃) (<i><b>trans</b></i><b>-5b</b> and <i><b>cis</b></i><b>-5b</b>) and Cp*­(CO)₂W­[CC­(SiPh₂·py)­(SiMe₃)] (<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*­(CO)₂W­(SiPh₂)­(CC^<i>t</i>Bu) (<b>1a</b>) with 4-(dimethylamino)­pyridine (DMAP) gave an equilibrium mixture of DMAP-stabilized silylene acetylide complexes <i>trans-</i> and <i>cis</i>-Cp*­(CO)₂W­(SiPh₂·DMAP)­(CC^<i>t</i>Bu) (<i><b>trans</b></i><b>-4</b> and <i><b>cis</b></i><b>-4</b>). The corresponding reaction using Cp*­(CO)₂W­(SiPh₂)­(CCSiMe₃) (<b>2</b>) produced the novel DMAP-coordinated silenylcarbyne/silylvinylidene complex Cp*­(CO)₂W­[CC­(SiPh₂·DMAP)­(SiMe₃)] (<b>6a</b>) as a major product, which was equilibrated with <i>trans-</i> and <i>cis</i>-Cp*­(CO)₂W­(SiPh₂·DMAP)­(CCSiMe₃) (<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*­(CO)₂W­(SiPh₂·py)­(CCSiMe₃) (<i><b>trans</b></i><b>-5b</b> and <i><b>cis</b></i><b>-5b</b>) and Cp*­(CO)₂W­[CC­(SiPh₂·py)­(SiMe₃)] (<b>6b</b>) at low temperature, while a mixture of <b>1a</b> and pyridine showed no such spectral changes