Formation of Derivative Carbyne Complexes from Tp‘(CO)<sub>2</sub>M⋮CCH<sub>3</sub> (M = Mo, W)

Chloride displacement from Tp‘(CO)<sub>2</sub>M⋮CCl (M = Mo, W (<b>1</b>); Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) with LiMe<sub>2</sub>Cu affords the methylcarbyne complex Tp‘(CO)<sub>2</sub>M⋮CCH<sub>3</sub> (M = Mo (<b>2</b>), W (<b>3</b>)). Deprotonation of this methylcarbyne forms [Tp‘(CO)<sub>2</sub>M=CCH<sub>2</sub>]<sup>-</sup> (M = Mo, W (<b>4</b>)), a nucleophilic vinylidene anion which reacts with a variety of substrates. Reaction of <b>4</b> with CH<sub>3</sub>I yields Tp‘(CO)<sub>2</sub>W⋮CCH<sub>2</sub>CH<sub>3</sub> (<b>5</b>), while PhC(O)H yields Tp‘(CO)<sub>2</sub>W⋮CCH<sub>2</sub>CH(OH)(Ph) (<b>8</b>) and PhC(O)CH<sub>3</sub> yields Tp‘(CO)<sub>2</sub>W⋮CCH<sub>2</sub>C(OH)(CH<sub>3</sub>)(Ph) (<b>10</b>). In the presence of base complex <b>8</b> undergoes elimination to form a conjugated vinyl carbyne complex Tp‘(CO)<sub>2</sub>W⋮CCHCH(Ph) (<b>11</b>). Reaction of <b>4</b> with PhC(O)Cl and then base forms Tp‘(CO)<sub>2</sub>W⋮CCH<sub>2</sub>C(O)Ph (<b>14</b>), which rearranges in solution to a metallafuran complex, (<b>15</b>). Spectroscopic data suggests that a dinuclear intermediate, Tp‘(CO)<sub>2</sub>W⋮CCH<sub>2</sub>CPh(OH)CH<sub>2</sub>C⋮W(CO)<sub>2</sub>Tp‘ (<b>13</b>), is first formed from <b>4</b> and PhC(O)Cl before the addition of base produces the expected monomeric product, Tp‘(CO)<sub>2</sub>W⋮CCH<sub>2</sub>C(O)Ph (<b>14</b>).