[2 + 2] Cycloaddition Products of Zirconium and Hafnium Hydrazinediides with Allenes and Heteroallenes and Their Thermally Induced Rearrangements

Abstract

Reactions of the hydrazinediido complexes [M(N 2 TBS N py )(NNPh 2 )(py)] (M = Zr ( 1a ), Hf ( 1b )) with (hetero)allenes result in a variety of [2 + 2] cycloaddition products of the general type [M(N 2 TBS N py )(κ 2 N,E -(E(═E′R)NNPh 2 )(py)] (E = CH 2, S; E′ = CH, N; R = alkyl, aryl). The reaction of [Zr(N 2 TBS N py )(NNPh 2 )(py)] ( 1a ) with 1 molar equiv of phenyl or mesityl isothiocyanate at room temperature yields [Zr(N 2 TBS N py )(κ 2 N,S -SC(═NAr)NNPh 2 )(py)] (Ar = phenyl ( 2a ), mesityl ( 2b )). Reacting the hydrazinediides [M(N 2 TBS N py )(NNPh 2 )(py)] (M = Zr ( 1a ), Hf ( 1b )) with allenes results in the formation of the metallaazacyclobutanes [M(N 2 TBS N py )(κ 2 N, C -N(NPh 2 )CH 2 C═CH(R))(py)] (M = Zr, R = Ph ( 4a ), cyclohexyl ( 5a ), methyl ( 6 ); M = Hf, R = phenyl ( 4b ), cyclohexyl ( 5b )). Subsequent heating of the cycloaddition products revealed different reactivity patterns: the complex [Zr(N 2 TBS N py )(κ 2 N,S -SC(═NAr)NNPh 2 )(py)] ( 2a ) forms the isomerization product [Zr(N 2 TBS N py )(κ 2 N,S- SC(═NNPh 2 ))NPh] ( 3 ), retaining the N–N bond of the hydrazide. In contrast, the metallacyclobutanes 4a, b and 5a, b show a tendency toward N–N bond cleavage, resulting in the formation of the C–N- and C–C-coupled product complexes [M(κ 4 N,N,N,N -N 2 TBS N py NC(Me)═CHCy)(NPh 2 )] (M = Zr ( 7a ), Hf ( 7b )), [Zr(N 2 TBS N py )(κ 2 N,C- (Ph)NC 6 H 4 C(Me)═C(Ph)NH)] ( 8 ) and [Zr(κ 4 N,N,N,N -N 2 TBS N py NC(Me)=CHPh)(NPh 2 )] ( 9 ).