Formation and Reactivity of the [Cp‘2Ta(H)2]+Cation (Cp‘ = η5-tBuC5H4)

The complex Cp‘2Ta(H)(OCOCF3)2 (2) is synthesized by the acidolysis of Cp‘2TaH3 (1) (Cp‘ = η5-tBuC5H4) in the presence of an excess of trifluoroacetic acid. 1 undergoes a loss of H- upon the reaction of electrophile (H+ or CPh3+). The resulting cation [Cp‘2Ta(H)2]+ ([3]+) can be isolated as a solvento adduct [Cp‘2Ta(H)2(SMe2)]BF4 (4·BF4) by carring out the reaction in dimethyl sulfide. Oxidation of 1 by means of ferrocenium hexafluorophosphate gives 4·PF6. Coordination of various neutral two-electron-donor L ligands affords the corresponding cationic species [Cp‘2Ta(H)2(L)]+ as BF4 or PF6 salts with L = tetrahydrothiophene (5), CN-tBu (6), PMe2Ph (8), and CO (9). Microanalytical, mass spectrometric, and infrared and NMR (1H, 19F, 31P) spectroscopic data for the complexes are reported, along with the X-ray crystal structure of [Cp‘2Ta(H)2(SMe2)]BF4 (4·BF4). The structural and spectroscopic properties of the dihydride complexes (4−8, 12, and 13) are consistent with a central position of the ligand at the ta...