Alkyne activation by half-sandwich ruthenium(II) complexes bearing the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane (PTA)

Complex [RuCl{κ3(N,N,N)-Tp}(PPh3)(PTA)] (κ3(N,N,N)-Tp = hydridotris(pyrazolyl)borate) containing the water-soluble phosphane 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane (PTA) reacts with terminal alkynes producing to the corresponding neutral alkynyl complexes [Ru(CCR){κ3(N,N,N)-Tp}(PPh3)(PTA)] (R = Ph (1a), nBu (1b), 1-cyclopentenyl (1c), p-methoxyphenyl (1d), 6-methoxynaft-2-yl (1e)). When halide is extracted from complex [RuCl{κ3(N,N,N)-Tp}(PPh3)(PTA)] followed by treatment with propargyl alcohols, the corresponding allenylidene complexes [Ru{κ3(N,N,N)-Tp}(PPh3)(PTA)(CCCPh2)][X] (X = PF6 (2a), CF3SO3 (2b)) and [Ru{κ3(N,N,N)-Tp}(PPh3)(PTA)(CCCC12H8)][PF6] (3) result. Electrophilic attack on the complexes thus obtained leads chemoselectively to the alkynyl complexes [Ru(CCR){κ3(N,N,N)-Tp}(PPh3)(1-CH3-PTA)][CF3SO3] (R = Ph (4a), nBu (4b), and 1-cyclopentenyl (4c)) and to the dicationic allenylidene complexes [Ru{κ3(N,N,N)-Tp}(PPh3)(1-H-PTA)(CCCC12H8)][PF6]2 (5) and [Ru{κ3(N,N,N)-Tp}(PPh3)(1-CH3-PTA)(CCCPh2)][CF3SO3]2 (6).

Graphical abstractNovel alkynyl [Ru(CCR){κ3(N,N,N)-Tp}(PPh3)(PTA)] and allenylidene [Ru{κ3(N,N,N)-Tp}(PPh3)(PTA)(CCCR2)][X] complexes have been isolated and characterized. Electrophilic attack led chemoselectively to the alkylation of the PTA ligand and no electrophilic attacks to the β-carbon of the alkynyl or to the allenylidene complexes have been detected.Figure optionsDownload full-size imageDownload as PowerPoint slide