Hydrogenolysis of Cationic Half‐Sandwich Zinc Complexes Containing a Chelating Amine: Facile Cleavage of Zinc‐Carbon Bond by Dihydrogen to Give Zinc Hydride Cations

Cationic half‐sandwich zinc complexes containing chelating amines [Cp*Zn(L n )][BAr 4 F ] ( 2 a , Cp*=η 3 ‐C 5 Me 5 , L n = N , N , N ’, N ’‐tetramethylethylenediamine, TMEDA; 2 b , L n = N , N , N ’, N ’‐tetraethylethylenediamine, TEEDA; 2 c , Cp*=η 1 ‐C 5 Me 5 , L n = N , N , N ’, N ’’, N ’’‐pentamethyldiethylenetriamine, PMDTA; Ar 4 F =(3,5‐(CF 3 ) 2 C 6 H 3 ) 4 ) reacted with dihydrogen (ca. 2 bar) in THF at 80 °C to give molecular zinc hydride cations [(L n )ZnH(thf) m ][BAr 4 F ] ( 3 a , b , m=1; 3 c , m=0) previously reported along with Cp*H. Pseudo first‐order kinetics with respect to the concentration of 2 b suggests heterolytic cleavage of dihydrogen by the Zn−Cp* bond, reminiscent of σ‐bond metathesis. Hydrogenolysis of the zinc cation 2 b in the presence of benzophenone gave the zinc alkoxide [(TEEDA)Zn(OCHPh 2 )(thf)][BAr 4 F ] ( 5 b ). Cation 2 b was shown to catalytically hydrogenate N ‐benzylideneaniline. The PMDTA complex 2 c underwent C−H bond activation in acetonitrile to give a dinuclear μ‐κC,κN‐cyanomethyl zinc complex [(PMDTA)Zn(CH 2 CN)] 2 [BAr 4 F ] 2 ( 6 c ).