Synthesis and Reactivity of RuCp*(κ2(P,N)-Ph2PCH2CH2NMe2)Cl. Chelate-Assisted Methyl C−H Activation and Formation of the Novel Complex [RuCp*(κ3(P,N,C)- Ph2PCH2CH2N(CH2)Me)Cl]BPh4

RuCp*(κ 2 ( P, N )-Ph 2 PCH 2 CH 2 NMe 2 )Cl ( 1 ) is afforded in 87% yield by the reaction of RuCp*(η 4 -isoprene)Cl with 1 equiv of Ph 2 PCH 2 CH 2 NMe 2 in CH 2 Cl 2 as the solvent. The hemilabile nature of the Ph 2 PCH 2 CH 2 NMe 2 ligand in 1 is revealed by the reaction with carbon monoxide, whereupon the neutral complex RuCp*(κ 1 ( P )-Ph 2 PCH 2 CH 2 NMe 2 )(Cl)(CO) ( 2 ) is obtained bearing the Ph 2 PCH 2 CH 2 NMe 2 ligand in κ 1 (P)-coordinated fashion. Chloride abstraction from 1 with TlCF 3 SO 3 led to RuCp*(κ 2 ( P, N )-Ph 2 PCH 2 CH 2 NMe 2 )(η 1 -OSO 2 CF 3 ) ( 3 ), where CF 3 SO 3 - is directly bound to the metal center. Both 1 and 3 are convenient precursors for the synthesis of the cationic vinylidene complex [RuCp*(κ 2 ( P, N )-Ph 2 PCH 2 CH 2 NMe 2 )( C CHPh)] + ( 4 ). When chloride abstraction from 1 was performed with NaBPh 4 in CH 2 Cl 2 instead of TlCF 3 SO 3 in tetrahydrofuran as the solvent, the novel cationic Ru(IV) complex [RuCp*(κ 3 ( P, N, C )-Ph 2 PCH 2 CH 2 N(CH 2 )Me)Cl] + ( 5 ) was formed. This reaction likely proceeds via the cationic 16e - complex [RuCp*(κ 2 ( P, N )-Ph 2 PCH 2 CH 2 NMe 2 )] +, which then readily undergoes methyl β-hydrogen elimination to give the cyclometalated cationic hydrido complex [RuCp*(κ 3 ( P, N, C )-Ph 2 PCH 2 CH 2 N(CH 2 )Me)H] + . This latter complex is trapped in CH 2 Cl 2 or CD 2 Cl 2 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, SiMe 3, 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.