Early-Transition-Metal Ketenimine Complexes:  Synthesis, Reactivity, and Structure of Ketenimine-Containing Titanocene and Zirconocene Complexes

• Published in: Organometallics Vol. 16; no. 24; pp. 5283 - 5288
• Main Authors: Fandos, Rosa, Lanfranchi, Maurizio, Otero, Antonio, Pellinghelli, María Angela, Ruiz, M. José, Teuben, Jan H
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 25.11.1997; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; HETEROALLENE COMPLEXES; SYSTEM; KETENE COMPLEXES; NIOBIUM; MOLECULAR-STRUCTURE; HYDRIDES; ISOCYANIDES; CHEMISTRY; LIGAND; CARBYNE COMPLEXES
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om970568p

Reaction of Cp2M(PMe3)2 complexes (M = Ti, Zr; Cp = η5-C5H5) with the N-(p-tolyl)diphenylketenimine Ph‘NCCPh2 (Ph‘ = p-MeC6H4) in a 1:1 molar ratio affords the ketenimine-containing metallocene derivatives Cp2M(η2-(C,N)-Ph‘NCCPh2)(PMe3) (M = Ti (1); Zr (2)). The ketenimine ligand reacts in the same way with the “Cp*2M” species (Cp* = η5-C5Me5) generated from the reduction of the corresponding Cp*2MCl2 complexes with LitBu (1:2 molar ratio) to give the related complexes Cp*2M(η2-(C,N)-Ph‘NCCPh2) (M = Ti (3); Zr (4)). The molecular structure of 3 shows a titanium atom bonded to two η5-cyclopentadienyl rings and a η2 -(C,N)-bonded ketenimine ligand. Reaction of “Cp*2Ti” with the ketenimine ligand in a 1:2 molar ratio gives 1,1,5,5-tetraphenyl-3-(p-tolyl)-2-(p-toluidino)-3-aza-1,4-pentadiene, which probably results from the coupling, followed by hydrolysis, of two ketenimine molecules coordinated to one titanocene moiety. Protonation of 3 with Et3NHCl or H2O (1:1 molar ratio) affords the intermediate species Cp*2Ti(X)(η2-(C,N)-Ph‘N C(H) CPh2) (X = Cl (5); OH (6)), which on hydrolysis evolves to give the enamine Ph‘N(H)CHCPh2 as the final product. Finally, 3 reacts reversibly with H2 to give the hydride enamidate complex Cp*2Ti(H)(η1-Ph‘NCHCPh2) (7). The structures of the different compounds have been determined by IR and NMR spectroscopic methods.