Reactions of Group 4 Metallocenes with N , N ′‐Diphenylformamidine – Hydrogen Generation versus Oxidative Addition

Reactions of Cp 2 M (L)(η 2 ‐Me 3 SiC 2 SiMe 3 ) (Cp = η 5 ‐cyclopentadienyl) ( 1 ‐ Ti : M = Ti, no L; 1 ‐ Zr : M = Zr, L = pyridine) with PhN=C(H)–N(H)Ph are discussed, giving for titanium the formation of hydrogen together with the four‐membered Ti III metallacycle Cp 2 Ti(κ 2 ‐ N , N ′‐PhN–C(H)–NPh) ( 2 ). For zirconium in the same reaction at elevated temperature the Zr IV complex Cp 2 Zr(H)(κ 2 ‐ N , N ′‐PhN–C(H)–NPh) ( 3 ) and at ambient temperature, as an intermediate for this, the σ‐alkenyl complex Cp 2 Zr[C(SiMe 3 )C=CH(SiMe 3 )](κ 2 ‐ N , N ′‐PhN–C(H)–NPh)] ( 4 ) were formed. Alternatively, metallation of PhN=C(H)–N(H)Ph and its subsequent reaction with [Cp 2 TiCl] 2 gave 2 and with Schwartz's reagent Cp 2 Zr(H)(Cl) complex 3 . Complex 2 reacts with additional Cp 2 Ti(η 2 ‐Me 3 SiC 2 SiMe 3 ) ( 1 ‐ Ti ) but there are no hints for the expected reduction of the PhN=C(H)–N(H)Ph unit to PhN=C=NPh by further C–H bond activation, the formation of hydrogen and products of the assumed unstable intermediate [Cp 2 Ti(κ 2 ‐ N , N ′‐Ph–N=C=N–Ph)]. The molecular structure of complex 2 was determined by X‐ray analysis.