Hydride and Proton Transfer Reactions of Niobium-Bound Ligands. Synthetic and Thermodynamic Studies of Ketene, Enacyl, and Vinylketene Complexes

Autor:	Azzam S. Hneihen, a Joseph W. Bruno, a Niladri Sarker, b and Gayle K. Schulte, a Margaret E. Kerr
Rok vydání:	2000
Předmět:	Allylic rearrangement Addition reaction Tetrafluoroborate Chemistry Hydride Ligand Organic Chemistry Substituent Ketene Medicinal chemistry Inorganic Chemistry chemistry.chemical_compound Electrophile Organic chemistry Physical and Theoretical Chemistry
Zdroj:	Organometallics. 19:901-912
ISSN:	1520-6041 0276-7333
DOI:	10.1021/om9907066
Popis:	The niobium ketene complexes Cp‘2Nb(Cl)(OCC(R‘)CH2R) (1; Cp‘ = η5-C5H4SiMe3) exhibit complexation of the ketene CO bond. Upon treatment with an appropriate triarylcarbenium tetrafluoroborate they donate a hydride, a process constituting a useful synthesis of the η2-enacyl salts [Cp‘2Nb(Cl)(η2-OCC(R‘)CHR)][BF4] (3). The reactions involve transfer of a γ-hydride and are specific for the generation of the (E)-enacyl isomers; one derivative (3b, R‘ = Ph, R = Me) was the subject of an X-ray diffraction study. The cationic enacyls are strong electrophiles and are susceptible to conjugate addition reactions and [4 + 2] cycloadditions. If the substituent R contains allylic protons, the enacyl complex is also very acidic; treatment with a suitable base converts these enacyls to the η2(C,O)-vinylketene complexes Cp‘2Nb(Cl)(η2-OCC(R‘)CHCH2) (7). These compounds are relatively electron-rich, and the vinyl terminus constitutes a site for addition of electrophiles. The overall conversion of ketene ligand to vinylketene...
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::8ed680354505ad1319ea6ed36558294b https://doi.org/10.1021/om9907066 Zobrazit plný text záznamu