Functional ruthenium (II) allenylidene and diynyl (arene) derivatives formed by activation of a diyne via a Ru=C=C=C=C=CR2 intermediate

Article abstract of DOI:10.1021/om00007a036

The activation of the diyne HC≡CC≡CC(OSiMe₃)Ph₂ (II) by a variety of RuCl₂(PR₃)(C₆-Me₆) complexes 1 [PR₃ = PMe₃(a), PMe₂Ph (b), PMePh₂(c)], in the presence of the salt NaPF₆, selectively leads either to [L_nRu=C(OMe)CH=C=C=CR₂]PF₆ (3), [L_nRu=C=C=C(OR)-CH=CR₂]PF₆ (4-6), [L_nRu=C=C=C(NR′₂)CH=CR₂]PF₆ (7), or [L_nRu-C≡CC≡CC(OSiMe₃)-Ph₂]PF ₆ (8), (L_nRu = RuCl(PR₃)(C₆Me₆)). In methanol 1a leads to the buta-1,2,3-trienylcarbene complex 3 and the 3-alkenylallenylidene derivative 4a. In ethanol and 2-propanol the complexes containing the 3-alkenylallenylidene moiety 5a-c and 6a-c are generated from 1a-c. In the presence of HNPh₂ the derivatives [L_nRu=C=C=C(NPh₂)CH=CPh₂]PF₆ (7a-c) are obtained, whereas in the presence of HNⁱPr₂, NEt₃ or, Bu^tNH₂ and NaPF₆ the diynyl derivatives 8a-c are selectively produced. The protonation with HBF₄ of the diynyl complexes 8 in the presence of alcohol or diphenylamine is shown to displace the OSiMe₃ group and generate (3-alkenylallenylidene)ruthenium derivatives 6-7*. The activation of the diyne II by complexes 1 and NaPF₆ can be rationalized in terms of the formation of the electrophilic penta-1,2,3,4-tetraenylidene intermediate [(C₆Me₆)(PR₃)Cl Ru=C=C=C=C=CPh₂]⁺ (2), which is reactive toward weak nucleophiles.