Hydrogen transfer to carbonyls and imines from a hydroxycyclopentadienyl ruthenium hydride: Evidence for concerted hydride and proton transfer
Hydrogen transfer to carbonyls and imines from a hydroxycyclopentadienyl ruthenium hydride: Evidence for concerted hydride and proton transfer
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DOI：
10.1021/ja002177z
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发表时间：
2001-02-14
影响因子：
15
通讯作者：
Kavana, M
中科院分区：
文献类型：
--
作者：
Casey, CP;Singer, SW;Kavana, M
[2，5-Ph-2-3，4-Tol(2)(ETA(5)-C4CO)](2)H}Ru-2(CO)(4)(Mu-H)(6)与H-2反应生成[2，5-Ph-2-3，4-Tol(2)(ETA 5-C4COH)Ru(CO)(2)H](8)。在温度为-10℃的四氢呋喃中，PhCHO被8还原的反应动力学为二级动力学，其中DeltaH(双匕首)=12.0kcal mol(-1)，Deltas(双匕首)=-28EU。CF3CO2H不加速还原速度，CO也不抑制还原速度。对于PPhCHO在0℃下的还原，保留了个别动力学同位素效应k(RuH)/k(Rud)=1.5+/-0.2和k(OH)/k(OD)=2.2+/-0.1。在8中同时进行两个位置的氢化反应，得到了k(OHRuH)/k(ODRuD)=3.6+/-0.3的联合动力学同位素效应。[2，5-Ph-2-3，4-Tol(2)(ETA(5)-C4COSiEt3)Ru(CO)(2)H](12)和Net4+[2，5-Ph-2-3，3-Tol(2)(ETA(4)-C4CO)Ru(CO)(2)H](-)(13)对PhCHO无反应。PhCOMe比PhCHO慢8~30倍，MEN=CHPh比PhCHO快8~26倍。只有在H-2存在的情况下，环己烯才能在80℃下还原为环己烷。提出了一个质子从氢氧基和氢化物从Ru(8)到羰基和亚胺的协同转移。
Reaction of {[2,5-Ph-2-3,4-Tol(2)(eta (5)-C4CO)](2)H}Ru-2(CO)(4)(mu -H) (6) with H-2 formed [2,5-Ph-2-3,4-Tol(2)(eta 5-C4COH)Ru(CO)(2)H] (8), the active species in catalytic carbonyl reductions developed by Shvo. Kinetic studies of the reduction of PhCHO by 8 in THF at -10 degreesC showed second-order kinetics with DeltaH(double dagger) = 12.0 kcal mol(-1) and DeltaS(double dagger) = -28 eu. The rate of reduction was not accelerated by CF3CO2H, and was not inhibited by CO. Selective deuteration of the RuH and OH positions in 8 Save individual kinetic isotope effects k(RuH)/k(RuD) = 1.5 +/- 0.2 and k(OH)/k(OD) = 2.2 +/- 0.1 for PhCHO reduction at 0 degreesC. Simultaneous deuteration of both positions in 8 gave a combined kinetic isotope effect of k(OHRuH)/k(ODRuD) = 3.6 +/- 0.3. [2,5-Ph-2-3,4-Tol(2)(eta (5)-C4COSiEt3)Ru(CO)(2)H] (12) and NEt4+[2,5-Ph-2-3,3-Tol(2)(eta (4)-C4CO)Ru(CO)(2)H](-) (13) were unreactive toward PhCHO under conditions where facile PhCHO reduction by 8 occurred. PhCOMe was reduced by 8 30 times slower than PhCHO; MeN=CHPh was reduced by 8 26 times faster than PhCHO. Cyclohexene was reduced to cyclohexane by 8 at 80 degreesC only in the presence of H-2. Concerted transfer of a proton from OH and hydride from Ru of 8 to carbonyls and imines is proposed.