Structures and Reactivity of Zr(IV) Chlorobenzene Complexes

The synthesis, structures, and unusual reactivity of (C5R5)2ZrR‘(ClPh)+ chlorobenzene complexes are described. The reaction of (C5R5)2ZrR‘2 with [Ph3C][B(C6F5)4] in C6D5Cl affords [(C5R5)2ZrR‘(ClC6D5)][B(C6F5)4] chlorobenzene complexes (1-d5, R‘ = CH2Ph and (C5R5)2 = (C5H5)2; 2a−d-d5, R‘ = Me and (C5R5)2 = rac-(1,2-ethylene(bis)indenyl) (2a), (C5H5)2 (2b), (C5H4Me)2 (2c), (C5Me5)2 (2d, C5Me5 = Cp*)). Complexes 1 and 2b,c are thermally robust but are converted to [{(C5R5)2Zr(μ-Cl)}2][B(C6F5)4]2 (4b,c) by a photochemical process in ClPh solution. In contrast, 2d undergoes facile thermal ortho-C−H activation to yield [Cp*2Zr(η2-C,Cl-2-Cl-C6H4)][B(C6F5)4] (5), which slowly rearranges to [(η4,η-C5Me5C6H4)Cp*ZrCl][B(C6F5)4] (6) via β-Cl elimination and benzyne insertion into a Zr−CCp* bond. The higher thermal reactivity of 2d versus that of 1 and 2b,c is attributed to steric crowding associated with the Cp* ligands of 2d, which forces a ClPh ortho-hydrogen close to the Zr−Me group.本文报道了(C5R5)₂ZrR‘(ClPh)⁺氯苯配合物（chlorobenzene complexes）的合成、结构及反常反应活性。将(C5R5)₂ZrR‘₂与[Ph₃C][B(C₆F₅)₄]在氘代氯苯(C₆D₅Cl)中反应，可得到[(C5R5)₂ZrR‘(ClC₆D₅)][B(C₆F₅)₄]型氯苯配合物：其中1-d₅的R‘为苄基(CH₂Ph)，且(C5R5)₂为双环戊二烯基((C₅H₅)₂)；2a−d-d₅的R‘为甲基(Me)，且(C5R5)₂分别为外消旋-1,2-亚乙基双(茚基)(rac-(1,2-ethylene(bis)indenyl))(2a)、双环戊二烯基((C₅H₅)₂)(2b)、双(甲基环戊二烯基)((C₅H₄Me)₂)(2c)以及双(五甲基环戊二烯基)(Cp*, pentamethylcyclopentadienyl)₂(2d，其中Cp*为五甲基环戊二烯基(pentamethylcyclopentadienyl))。 配合物1与2b、2c具有优异的热稳定性，但在氯苯(ClPh)溶液中经光化学过程可转化为[{(C5R5)₂Zr(μ-Cl)}₂][B(C₆F₅)₄]₂(4b、4c)。与之形成鲜明对比的是，2d可快速发生热诱导的邻位C−H键活化，生成[Cp*₂Zr(η²-C,Cl-2-Cl-C₆H₄)][B(C₆F₅)₄](5)；该产物会通过β-氯消除(β-Cl elimination)及苯炔插入Zr−CCp*键的过程，缓慢重排为[(η⁴,η-C₅Me₅C₆H₄)Cp*ZrCl][B(C₆F₅)₄](6)。 相较于1及2b、2c，2d展现出更高的热反应活性，这一现象可归因于2d中Cp*配体带来的空间位阻效应：该效应迫使氯苯的邻位氢原子靠近Zr−Me键。