Synthesis, characterization, and thermal rearrangement of zirconium tetraazadienyl and pentaazadienyl complexes

摘要

Reaction of the zirconium dichloro complex [Zr(N _2 ~(TBS)N _(py))Cl _2] (1) with 1 molar equiv of ArNHLi (Ar = Mes, DIPP) yielded the zirconium imido complexes [Zr(N _2 ~(TBS)N _(py))(=N ~(DIPP))(py)] (2; N _2 ~(TBS)N _(py) = [(2-C _5H _4N)C(CH _3){CH _2NSi(CH _3) _2tBu} _2] ~(2-), DIPP = 2,6-diisopropylphenyl) and [Zr(N _2 ~(TBS)N _(py))(=N ~(Mes))(py)] (3; Mes = mesityl). The imido complexes are converted to the tetraazadienido complexes [Zr(N _2 ~(TBS)N _(py))(N _(DIPP)N _2N ~(Ph))] (4) and Zr(N _2 ~(TBS)N _(py))(N ~(Mes)N _2N ~(Ph))] (5) by addition of phenyl azide, whereas the reaction of 2 or 3 with mesityl azide gave the alternative product 7, in which the azide is coupled with the CH activated ancillary tripod ligand. Reaction of 1 molar equiv of trimethylsilyl azide or 1-adamantyl azide with the previously reported hydrazinediido complex [Zr(N 2 TBSN py)(=NNPh 2)(py)] (9) at ambient temperature resulted in the formation of the five-membered zirconaacacycles [Zr(N _2 ~(TBS)N _(py))(N ~(TMS)N _3NPh _2)] (10) and [Zr(N _2 ~(TBS)N _(py))(N ~(Ad)N _3NPh _2)] (11). Complex 11 was thermally converted into the diazenido complex 12 via loss of 1 molar equiv of molecular N _2. The direct formation of the analogous side-on-bonded diazenido analogue 13 was observed upon reaction of 9 with 1 equiv of mesityl azide at ambient temperature. On the basis of ~(15)N labeling and DFT modeling (DFT(B3PW91/6-31 g(d))) a mechanism for the reaction pathway leading to 12 and 13 is proposed.