Reactivity of [Re(eta(2)-H-2)(CO)(2)P-3](+) cations with alkynes: preparation of vinylidene and propadienylidene complexes

Treatment of [Re(eta(2)-H-2(CO)(2)P-3](+) cations with phenylacetylene lead s to the displacement of H-2 and the formation of vinylidene [Re{C=C(H)Ph}( CO)(2)P-3](+) (1-3) [P = P(OEt)(3), PPh(OEt)(2) or PPh2OEt] derivatives. In frared and NMR data support equilibrium in solution [Re(CO)(2)P-3](+) + PhC =H reversible arrow [Re{=C=C(H)Ph}(CO)(2)P-3](+) involving the unsaturated complex, free alkyne and vinylidene derivative. 1,4-Diethynylbenzene also t automerises to the Re(I) centre, affording the [Re{=C=C(PI)(1,4-C6H4C=CH)}( CO)(2)P-3]BF4 [P = P(OEt)(3) or PPh(OEt)(2)] vinylidene derivatives. Vinyli dene complexes 1-3 are deprotonated easily by NEt3 to give acetylides Re(C= CR)(CO)(2)P-3 (4-6) (R=Ph or 1,4-C6H4C=CH), which may in turn be reprotonat ed with HBF4. Et2O to reform vinylidenes 1-3. Acetylide complexes 4-6 were also prepared by reacting unsaturated cations [Re(CO)(2)P-3](+) with lithiu m acetylide. Binuclear complexes {Re(CO)(2)P-3}(2)(mu-1,4-C=CC6H4C=C) (7, 8 ) [P = PPh(OEt)(2) or PPh2OEt] were obtained by sequential treatment of [Re (CO)(2)P-3](+) cations, first with 1,4-HC=CC6H4C=CH and then with an excess of NEt3. Propadienylidene complexes [Re(=C=C=CPh2)(CO)(2)P-3]BF4 (9, 10) [ P=PPh(OEt)(2) or PPh2OEt] were prepared by allowing[Re(eta(2)-H-2)(CO)(2)P- 3](+) cations or unsaturated species [Re(CO)(2)P-3](+) to react with HC=CC( Ph-2)OH at room temperature. The characterisation of all new complexes by I R and H-1-, P-31{H-1}- and C-13{H-1}-NMR spectra is also discussed. (C) 200 0 Elsevier Science S.A. All rights reserved.