Enhanced Reactivity Results in Reduced Catalytic Performance:  Unexpected Ligand Reactivity of a Bis(N-2,6-diisopropylphenylperflourophenyl-amidate)titanium-bis(diethylamido) Hydroamination Precatalyst

• Published in: Organometallics Vol. 26; no. 25; pp. 6366 - 6372
• Main Authors: Bexrud, Jason A., Li, Chunyu, Schafer, Laurel L.
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 03.12.2007; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; ZIRCONIUM; TI; INTERMOLECULAR HYDROAMINATION; ASYMMETRIC HYDROAMINATION; INTRAMOLECULAR HYDROAMINATION; ANTI-MARKOVNIKOV HYDROAMINATION; IMIDO COMPLEX; TITANIUM; ALKYNES; AMIDATE COMPLEXES
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om700653t

A bis(amidate)titanium-bis(amido) complex incorporating electron withdrawing pentafluorophenyl substituents has been prepared to enhance reactivity in this class of hydroamination precatalyst. This bis(N-2,6-diisopropylphenylperflourophenylamidate)titanium-bis(diethylamido) titanium complex has been fully characterized, including its X-ray crystal structure. As a precatalyst, the title compound proved to be effective for intermolecular hydroamination of internal and terminal alkynes with primary amines with yields as high as 97% and modest intramolecular alkene hydroamination. However, the elevated reactivity of this complex also resulted in reduced Markovnikov/anti-Markovnikov selectivity with some terminal alkynes. Substrate scope limitations revealed that this complex is susceptible to decomposition as a direct consequence of nucleophilic addition of the amine substrate to the pentafluorophenyl substituent of the amidate ligand.