Reactions of [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(COD) with Lewis bases: Synthesis, structure, and electrochemistry of ruthenium amine, nitrile, carbene, phosphite and phosphine complexes

Treatment of [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(COD) (1) with phosphites, phosphines, amines or N-heterocyclic carbene in THF afforded the COD displacement complexes [η5:σ-Me2C(C5H4)(C2B10H10)]Ru[P(OEt)3]2 (2), [η5:σ-Me2C(C5H4)(C2B10H10)]Ru[PPh2(OEt)]2 (3), [η5:σ-Me2C(C5H4)(C2B10H10)]Ru[NH2CH2CH2Pri]2 (4), [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(NH2Prn)2 (5), [η5:σ-Me2C(C5H4)(C2B10H10)]Ru (η2-NH2CH2CH2NH2) (6), [η5:σ-Me2C(C5H4)(C2B10H10)]Ru[η2-NH(CH3)CH2CH2NH(CH3)] (7) or [η5:σ-Me2C(C5H4)(C2B10H10)]Ru[NHC]2 (8, NHC = 1,3,4,5-tetramethylimidazol-2-yilidene), respectively. Ruthenium–amine complexes were much more labile than 1. Upon exposure to moisture, 5 was converted into [{η5:σ-Me2C(C5H4)(C2B10H10)}Ru(μ-H2O)]2 (9). Reactions of 5 with PR3 (R = PPh3, Cy), TMEDA (TMEDA = N,N,N′,N′-tetramethylethylenediamine) and CH3CN afforded the corresponding amine replacement products[η5:σ-Me2C(C5H4)(C2B10H10)]Ru(NH2Prn)(PPh3) (10), [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(NH2Prn)(PCy3) (11), [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(TMEDA) (12) and [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(NCCH3)2 (13). These results indicated that the steric factor dominated these substitution reactions. The electrochemical studies showed that the electron richness of the Ru atom decreased in the order L2Ru(NHC)2 > L2Ru(amine)2 > L2Ru(NCMe)2 > L2Ru(P)2. All of these complexes were fully characterized by various spectroscopic techniques and elemental analyses. The molecular structures of 2, 3, 5–10, 12 and 13 were further confirmed by single-crystal X-ray analyses.

Ruthenium amine and acetonitrile complexes bearing a constrained-geometry carboranyl ligand are much more labile than the corresponding COD analogue, allowing the introduction of a variety of new ligands on the Ru site. Thus, they may be good candidates as catalyst precursors.Figure optionsDownload as PowerPoint slide