Reaktionen von bis(η-cyclopentadienyl)zirconiumhydriden mit (iminoacyl)zirconocen-komplexen

The reaction of imidoylzirconocene complexes with zirconocene hydrides yields (N-alkylamido)zirconocene complexes. For a mechanistic study, the specifically substituted imidoylzirconocene complexes 3b–3d have been prepared and treated with the oligomeric metal hydrides (Cp₂ZrH₂)_x (1b) and (Cp₂ZrHCl)_x (1c). (N-Benzyl formimidoyl)zirconocene chloride (3b) was obtained by treating 1c with benzyl isonitrile 2a. Treatment of dimethylzirconocene with 2a gave (N-benzyl acetimidoyl)methylzirconocene (3c), which was treated with PhICl₂ to give (N-benzylacetimidoyl)zirconocene chloride (3d). The reaction of 3d with (Cp₂ZrH₂)_x (1b) yielded (N-benzyl-N-ethylamido)zirconocene chloride (4b) as the only identified product. A 1/1 mixture of 4b and methylzirconocene chloride was obtained upon treatment of 3c with (Cp₂ZrHCl)_x (1c); in contrast, the reaction of 1c with 3b gave an equimolar mixture of Cp₂ZrCl₂ and (N-benzyl-N-methylamido)zirconocene chloride (4c). Reaction paths through binuclear (μ-CHR′=NR) zirconocene intermediates are proposed to explain these experimental observations.     

Reaktionen von (η-formaldehyd)zirconocen-dimer mit heterokumulenen

The (η²-formaldehyde)zirconocene dimer (Cp₂ H₂)₂ (7) inserts CO₂ into the zirconium to carbon bond of the metallaoxirane moiety to give [(Cp₂ H₂)(Cp₂ =O)] (8). Reaction with diphenylketene 7 gives the cyclodimeric 1 : 1 addition product (Cp₂ =CPh₂)₂ (10) via the mono-insertion product 9. Similarly, treatment of 7 with t-butylisocyanate yields the intermediate complex [(Cp₂ H₂)(Cp₂ =NCMe₃)] (11) which gives the final product (Cp₂ =NCMe₃)₂ (12). Here two five-membered metallacycles are joined together by oxygen bridges via a central four-membered Zr₂O₂ metallacycle. Complex 12 was characterized by X-ray diffraction. It crystallizes in space group P2₁/n with cell parameters a 10.142(1), b 17.949(2), c 12.001(1) Å, β = 114.27(1)°; Z = 2, R = 0.055, R_w = 0.054.