1,2-Bis(dimethylphosphino)ethanehydridomesitylidyne-tungsten(IV). Hydride activation via the trans influence

Article abstract of DOI:10.1021/om000332c

The synthesis of the tungsten carbyne hydride complex trans-W(CMes)(dmpe)₂H, 7, which is obtained from the borohydride complex trans-W(CMes)(η¹-BH₄)(dmpe)2, 6, (dmpe = Me₂-PCH₂CH₂PMe₂) is reported. 6 is readily prepared from trans-W(CMes)(dmpe)₂d, 5, which is prepared from [W(CO)₅C(O)Mes][N(CH₃)₄] via the isolable intermediates trans-W(CMes)-(CO)₂(Py)₂Cl, 2, and trans-W(CMes)(CO)[P(OMe)₃]₃Cl, 3. 7 was spectroscopically fully characterized, and reactivity studies have revealed its potential in hydrogen transfer reactions. The results of studies into the reactivity of the W-H bond toward small unsaturated molecules, such as propionaldehyde, benzaldehyde, acetone, acetophenone, and benzophenone, to give the corresponding alkoxides trans-W(CMes)(dmpe)₂(OCHR′R″) (R′ = H, R″ = Pr 9, R′ = H, R″ = Ph 10, R′ = R″ = Me 11, R′ = Me, R″ = Ph 12, R′ = R″ - Ph 13) are presented. Facile insertion of the C=O moiety into the W-H bond was also observed with CO₂ to yield the formato-O-complex trans-W(CMes)(dmpe)₂(OCHO), 8. Reaction of 7 with pyridine-2-carbaldehyde yields the insertion product trans-W(CMes)(η¹-methoxypyridine)(dmpe)₂, 14, but only at temperatures below 0°C. 14 decomposes within minutes at room temperature. Treating 7 with 4-hydroxybenzaldehyde affords trans-W(CMes)(η¹-4-formylphenoxy)(dmpe)₂, 15, via a simple acid-base reaction with concomitant evolution of H₂.