Synthesis and reactivity of RuCp*(kappa(2)(P,N)-Ph2PCH2CH2NMe2)Cl. Chelate-assisted methyl C-H activation and formation of the novel complex [RuCp*(kappa(3)(P,N,C)-Ph2PCH2CH2N(CH2)Me)Cl]BPh4

RuCp*(kappa(2)(P,N)-Ph2PCH2CH2NMe2)Cl (1) is afforded in 87% yield by the reaction of RuCp*(eta(4)-isoprene)Cl with 1 equiv of Ph2PCH2CH2NMe2 in CH2Cl2 as the solvent. The hemilabile nature of the Ph2PCH2CH2NMe2 ligand in 1 is revealed by the reaction with carbon monoxide, whereupon the neutral complex RuCp*(kappa(1)(P)-Ph2PCH2CH2NMe2)(Cl)(CO) (2) is obtained bearing the Ph2PCH2CH2NMe2 ligand in kappa(1)(P)-coordinated fashion, Chloride abstraction from 1 with TlCF3SO3 led to RuCp*(kappa(2)(P,N)-Ph2PCH2CH2NMe2)(eta(1)-OSO2CF3) (3), where CF2SO3- is directly bound to the metal center. Both 1 and 3 are convenient precursors for the synthesis of the cationic vinylidene complex [RuCp*(kappa(2)(P,N)-Ph2PCH2CH2NMe2)(=C=CHPh)](+) (4). When chloride abstraction from 1 was performed with NaBPh4 in CH2Cl2 instead of TlCF3SO3 in tetrahydrofuran as the solvent, the novel cationic Ru(IV) complex [RuCp* (kappa(3)(P,N,C)-Ph2PCH2CH2N(CH2)Me)CI](+) (5) was formed. This reaction likely proceeds via the cationic 16e(-) complex [RuCp*(kappa(2)(P,N)-Ph2PCH2CH2NMe2)](+), which then readily undergoes methyl beta-hydrogen elimination to give the cyclometalated cationic hydride complex [RuCp*(kappa(3)(P,N,C)-Ph2PCH2CH2N(CH2)Me)H](+). This latter complex is trapped in CH2Cl2 or CD2Cl2 as the chloro complex 5. Preliminary results on the catalytic activity of 1 are also presented. Thus, 1 is shown to catalyze the dimerization and cyclotrimerization of some terminal alkynes HC=CR. Whereas with R = Ph, SiMe3, and n-Bu, isomeric mixtures of head-to-head and head-to-tail coupling products are obtained, in the case of R = COOEt, cyclotrimerization takes place exclusively. X-ray structures of complexes 1, 3, 4, and 5 are presented.