Metallacumulenes: Activation of diynes and formation of new allenylideneruthenium complexes. Crystal structures of trans-[(Ph2PCH2PPh2) 2(Cl)Ru=C=C=CR1R2]+ and trans-[(Ph2PCH2PPh2) 2Ru(=C=C=C(OMe)CH=CPh2)2]2+ derivatives

Article abstract of DOI:10.1021/om00011a050

cis-RuCl₂(Ph₂PCH₂PPh₂) ₂ (1) reacts with pentadiynes XC≡CC≡CCPh₂(OSiMe₃) [2 (X = H) and 3 (X = Bu₃Sn)], but in the presence of NaPF₆, to afford trans-(Ph₂PCH₂PPh₂) ₂(Cl)-RuC≡CC≡CCPh₂(OSiMe₃) (4). On protonation with HBF₄ complex 4 in methanol leads to allenylidene trans-[(Ph₂PCH₂PPh₂) ₂(Cl)Ru=C-C=C(OMe)CH=CPh₂]X (5a) (a: X = BF₄) and in dichloromethane to trans-[(Ph₂PCH₂PPh₂) ₂(Cl)Ru=C-C=CCH=C(Ph)(o-C₆H₄)]X (6a) via electrophilic ortho-substitution within the metallacumulene intermediate LnRu=C=C=C=C= CPh₂]X (A). Alternatively, complex 1 and diyne 2 with NaPF₆ afford in one step allenylidenes 5b (b: X = PF₆) in methanol and 6b in dichloromethane. Bis(diynyl) derivative trans-(Ph₂-PCH₂PPh₂) ₂Ru[(C≡CC≡CC(OSiMe₃)Ph₂]) ₂ (7), obtained by reaction of 2 with 1 and HNⁱPr₂, on protonation with HBF₄ in methanol offered a direct route to the first bis(allenylidene) complex trans-[(Ph₂PCH₂PPh₂) ₂Ru(=C=C=C(OMe)CH=CPh₂)₂](BF₄) ₂ (8). The X-ray diffraction studies of two allenylidene complexes 6b and 8 are reported. The structure of 6b consists of two different allenylidene cations. That of 8 shows coplanar allenylidene ligands with a strong contribution of a ynyl resonance structure.