定义Definition
格拉布斯催化剂是一类钌卡宾配合物，催化烯烃复分解反应（双键两端的亚烷基互换），包括关环复分解、交叉复分解和开环易位聚合。它们对空气、水和多种官能团耐受，易于操作。
Grubbs catalysts are ruthenium carbene complexes that catalyse olefin metathesis — the exchange of alkylidene fragments between double bonds — including ring-closing, cross and ring-opening metathesis polymerisation. They tolerate air, water and many functional groups and are easy to handle.
结构Structure
第一代：RuCl₂(=CHPh)(PCy₃)₂（1995）。第二代：一个 PCy₃ 换成 N-杂环卡宾（SIMes），活性和热稳定性大幅提高（1999）。霍维达–格拉布斯催化剂用螯合的异丙氧基苯亚甲基配体，更稳定、可回收。
First generation: RuCl₂(=CHPh)(PCy₃)₂ (1995). Second generation replaces one PCy₃ by an N-heterocyclic carbene (SIMes), greatly raising activity and thermal stability (1999). Hoveyda–Grubbs catalysts use a chelating isopropoxybenzylidene and are more robust and recyclable.
机理Mechanism
肖万机理：膦配体解离产生 14 电子活性物种；烯烃配位后与 Ru=C 发生 [2+2] 环加成形成金属杂环丁烷，再逆 [2+2] 断裂生成新烯烃和新的钌卡宾。关环复分解放出乙烯，由熵驱动。
Chauvin mechanism: phosphine loss gives a 14-electron species; the alkene binds and undergoes [2+2] cycloaddition with Ru=C to a metallacyclobutane, whose retro-[2+2] gives a new alkene and a new carbene. Ring-closing metathesis releases ethylene and is entropy-driven.
历史与意义History and significance
伊夫·肖万（1971）提出金属卡宾机理，理查德·施罗克发展了高活性钼、钨卡宾，罗伯特·格拉布斯发展了稳定易用的钌催化剂，三人共获 2005 年诺贝尔化学奖。烯烃复分解广泛用于药物大环（如丙肝药物）、聚合物和石化工业。
Yves Chauvin proposed the metal-carbene mechanism (1971), Richard Schrock developed highly active Mo/W carbenes, and Robert Grubbs developed robust ruthenium catalysts; they shared the 2005 Nobel Prize in Chemistry. Metathesis is used for macrocyclic drugs (e.g. HCV inhibitors), polymers and petrochemicals.
反应Reactions
1–5 mol% 催化剂，二氯甲烷或甲苯，室温至 40–80 °C；关环反应常在稀溶液中
1–5 mol% catalyst in CH₂Cl₂ or toluene, room temperature to 40–80 °C; ring closures in dilute solution
膦解离生成活性钌卡宾。
Phosphine dissociation gives the active carbene.
烯烃 [2+2] 环加成成金属杂环丁烷。
[2+2] cycloaddition to a metallacyclobutane.
逆 [2+2] 生成新烯烃和新卡宾，循环继续。
Retro-[2+2] gives a new alkene and carbene.
关环复分解。
Ring-closing metathesis.
化学性质Chemical properties
在空气中固态可短时操作，溶液中缓慢分解。
Handleable briefly in air as a solid; solutions decompose slowly.
对醇、酸、酯、酰胺、水等官能团耐受。
Tolerates alcohols, acids, esters, amides and water.
年表Timeline
- 1971
肖万提出金属卡宾机理
Chauvin proposes the metal-carbene mechanism
- 1995
第一代格拉布斯催化剂
First-generation Grubbs catalyst
- 1999
第二代（N-杂环卡宾）格拉布斯催化剂
Second-generation (NHC) Grubbs catalyst
- 2005
肖万、格拉布斯、施罗克获诺贝尔化学奖
Chauvin, Grubbs and Schrock share the Nobel Prize