The syntheses of several new bis(alkyne)(carbonyl)(η 5- cycloheptadienyl)tungsten(II) and bis(alkyne)-(carbonyl)(σ, η 3-cycloheptenediyl)tungsten(II) complexes are described. Addition of HBF 4·Et 2O to [(η 6-C 7H 8)W(CO) 3] (1) followed by treatment with diarylalkynes gave the cationic complexes [(η 5-C 7H 9)W(CO)(ArC≡CAr) 2][BF 4] (3a,b; Ar = C 6H 5,4-MeC 6H 4). These complexes react with nucleophiles LiHBEt 3, MeLi, and PhLi to form the neutral σ,η 3-cycloheptenediyl complexes [(σ,η 3-C 7H 9R)W(CO)-(ArC≡CAr) 2] (4a-e; R = H, Me, Ph), which contain η 1, η 2, and η 3 ligands. In all complexes, the two alkyne ligands act as net three-electron donors, although in the neutral complexes the two alkynes are inequivalent. The X-ray structure of [(σ,η 3-C 7H 9Ph)W(CO)(PhC≡CPh) 2] (4e) is reported. Complexes 4a,b (Ar = C 6H 5, 4-MeC 6H 4, R = H) can be converted back to the cations 3a,b using the triphenylcarbenium ion.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry