Synthesis of Alkylruthenium Nitrosyl Complexes. Migratory Insertion to Coordinated Nitric Oxide and the Mechanism of the Conversion of the Resultant Nitrosoalkyl Compounds to Oximate, Carboxamide, and Cyano Compounds

Article abstract of DOI:10.1021/ja00191a024

The compounds (η⁵-C5Me5)Ru(NO)R2 (2a, R = CH3; 2b R = CH2CH3) were synthesized by treating (η⁵-C5Me5)Ru(NO)Cl2 (1) with alkylating agents.Thermolysis of 2a with PMe3 gave (η⁵-C5Me5)Ru(PMe3)2CN (3), H2O, and CH4; heating 2b with PMe3 produced (η⁵-C5Me5)Ru((NO)CHCH3)(PMe3)2 (4) and ethane.The reaction of 1 with PhMgCl followed by protonolysis with HCl gave (η⁵-C5Me5)Ru(NO)(Ph)(Cl) (5); treatment of 5 with EtMgCl gave (η⁵-C5Me5)Ru(NO)(Ph)(Et) (6).Thermolysis of 6 with PMe3 gave 4; however, thermolysis of 6 with PPhMe2 led to the NO insertion product(η⁵-C5Me5)Ru(N(O)CH2CH3)(Ph)(PPhMe2) (8), characterized by X-ray diffraction (crystal data: space group P2₁/c; a = 8.6946 (6) Angstroem, b = 10.749 (1) Angstroem, c = 26.946 (3) Angstroem, β = 95.7 (4) deg; V = 2505.9 (8) Angstroem³; 3263 unique data, 2795 for which F² > 3?(F²); R = 2.20percent, wR = 2.98percent, GOF = 1.88).Heating complex 8 with PMe3 produced 4 while heating for extended periods with PPhMe2 gave (η⁵-C5Me5)Ru((NO)CHCH3)(PPhMe2)2 (9).The conversion of 8 to 9 was found to proceed under milder conditions in the presence of a strong Broensted base catalyst (e.g., NaOSiMe3); using CNBu^t in place of PPhMe2 afforded (η⁵-C5Me5)Ru((NO)CHCH3)(PPhMe2)(CNBu^t) (11).Treatment of 8 with the stronger base KN(SiMe3)2 in the presence of PPhMe2 led to (η⁵-C5Me5)Ru(Ph)(PPhMe2)2 (12) and KONCHCH3.Reaction of 8 with KN(SiMe3)2 and 18-crown-6 gave <(η⁵-C5Me5)Ru((NO)CHCH3)(Ph)(PPhMe2)>(-) (13).Complex 13 reacts with PPhMe2 to give 12 and with Et3SiOH and PPhMe2 to generate 9.Mechanistic studies, including kinetics, isotope effect, and tracer experiments, indicate that conversion of 8 to 4, 9, and 12 isinitiated by the base abstraction of a methylene proton of the nitrosoethane ligand.Upon furher thermolysis, 4 rearranges to (η⁵-C5Me5)Ru(N(H)C(O)CH3)(PMe3)2 (14).A possible mechanism for this transformation is discussed.