Activation of H–H, HO–H, C(sp2)–H, C(sp3)–H, and RO–H Bonds by Transition-Metal Frustrated Lewis Pairs Based on M/N (M = Rh, Ir) Couples

• Published in: Inorganic chemistry Vol. 61; no. 33; pp. 13149 - 13164
• Main Authors: Carmona, María, Pérez, Roberto, Ferrer, Joaquina, Rodríguez, Ricardo, Passarelli, Vincenzo, Lahoz, Fernando J., García-Orduña, Pilar, Carmona, Daniel
• Format: Journal Article
• Language: English
• Published: American Chemical Society 22-08-2022
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.2c01902

Reaction of the dimers [(Cp*MCl)2(μ-Cl)2] (Cp* = η5-C5Me5) with Ph2PCH2CH2NC­(NH­(p-Tolyl))2 (H2L) in the presence of NaSbF6 affords the chlorido complexes [Cp*MCl­(κ2 N,P-H2L)]­[SbF6] (M = Rh, 1; Ir, 2). Upon treatment with aqueous NaOH, solutions of 1 and 2 yield the corresponding complexes [Cp*M­(κ3 N,N′,P-HL)]­[SbF6] (M = Rh, 3; Ir, 4) in which the ligand HL presents a fac κ3 N,N′,P coordination mode. Treatment of THF solutions of complexes 3 and 4 with hydrogen gas, at room temperature, results in the formation of the metal hydrido-complexes [Cp*MH­(κ2 N,P-H2L)]­[SbF6] (M = Rh, 5; Ir, 6) in which the N­(p-Tolyl) group has been protonated. Complexes 3 and 4 react with deuterated water in a reversible fashion resulting in the gradual deuteration of the Cp* group. Heating at 383 K THF/H2O solutions of the complexes 3 and 4 affords the orthometalated complexes [Cp*M­(κ3 C,N,P-H2L‑H )]­[SbF6] [M = Rh, 7; Ir, 8, H2L‑H = Ph2PCH2CH2NC­(NH­(p-Tolyl))­(NH­(4-C6H3Me))], respectively. At 333 K, complexes 3 and 4 react in THF with methanol, primary alcohols, or 2-propanol giving the metal-hydrido complexes 5 and 6, respectively. The reaction involves the acceptorless dehydrogenation of the alcohols at a relatively low temperature, without the assistance of an external base. The new complexes have been characterized by the usual analytical and spectroscopic methods including the X-ray diffraction determination of the crystal structures of complexes 1–5, 7, and 8. Notably, the chlorido complexes 1 and 2 crystallize both as enantiopure conglomerates and as racemates. Reaction mechanisms are proposed based on stoichiometric reactions, nuclear magnetic resonance studies, and X-ray crystallography as well as density functional theory calculations.