SPONTANEOUS LOSS OF MOLECULAR HYDROGEN FROM TUNGSTEN(IV) ALKYL COMPLEXES TO GIVE ALKYLIDYNE COMPLEXES
SPONTANEOUS LOSS OF MOLECULAR HYDROGEN FROM TUNGSTEN(IV) ALKYL COMPLEXES TO GIVE ALKYLIDYNE COMPLEXES
复制标题
从钨(IV)烷基络合物中自发失去分子氢以得到烷基炔络合物
DOI：
10.1021/ja00105a081
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发表时间：
1994
影响因子：
15
通讯作者：
R. Schrock
中科院分区：
文献类型：
--
作者：
K. Shih;Karen M. Totland;S. Seidel;R. Schrock
我们已经开始探索钼和钨的化学包含triamidoamine配体的配合物,(R 'NCIhCHahN, R在收视甲硅烷基组(如SiMej) 1或cef·2(唯一的其他报道这类W或莫复杂[(MeNCH2-CH2) 3 n]莫= n . 3)我们发现顺[(R3SiNCH2-CH2) 3 n]莫(CH3)和[(R3SiNCH2CH2) 3 n]莫(C = CR”)(R3Si = Me3Si、PhMe2Si或Ph2MeSi; R”=我,Ph值,或SiMe3)复合物可以做好准备随时从[(R3SiNCH2CH2) 3 n] -MoCl。我们现在已经发现，尝试合成[(R'NCH2CH2) 3N] W（烷基）配合物通常会产生烷基炔配合物，即使在烷基中存在β质子。以WCl（1,2 -二甲氧基乙烷）或WCl4 (TOF) 2和配体（R3-SiNLiCH2CH2） 3N的三锂盐为原料，可在THF中以低收率（~ 20%）制备出单氯配合物[(R3SiNCH2CH2) 3N] WCl （R3-Si= Me3Si， Me2PhSi或MePh2Si）。（详见补充资料）甲基锂在乙醚中加入[(Me3SiNCH2CH2) 3N] WCl，产率高，顺磁性[(Me3SiNCH2CH2) 3N] W （CH3）。通过埃文的方法，在25℃时发现磁矩为2.5 pb，略小于两个未成对电子的预期自旋值（2.83 ps）。在25℃时，CeDe在31.43（半高宽度= wi/2= 40 Hz）和72.70 ppm （wi/2= 23 Hz）下可以观察到两个特征配体亚甲基共振，而TMS甲基共振在9.89 ppm下可以观察到。在2H核磁共振谱中，在7.5 ppm （wi/2= 5 Hz）下，[(Me3SiNCH2CH2) 3N] W （CD3）中CD3共振不能被观察到。4-6 [(Me3-SiNCH2CH2) 3N] W （CH3）几乎定量地转化为[(Me3SiNCH2CH2) 3N] W= CH (d (CK)= 272.6 ppm, JCw= 244 Hz,()= 7.08 ppm, Jhw= 81 Hz)（eq 1）在25和80 c之间。反应是一级的，经过几个半衰期，独立于浓度，超过5倍的范围（表1），由500 MHz的质子核磁共振通过遵循TMS共振强度的降低来确定。可以观察到分子氢的共振，尽管二氢在甲苯中的低溶解度-ág不允许用核磁共振定量。从表1的数据来看，AH*= 19.2 kcal mol-1, AS*= -16 eu
We have begun to explore the chemistry of Mo and W complexes that contain triamidoamine ligands,(R'NCIhCHahN, where R'is a silyl group (eg, SiMej) 1 or CeFs· 2 (The only other reported W or Mo complex in this category is [(MeNCH2-CH2) 3N] Mo= N. 3) We found that paramagnetic [(R3SiNCH2-CH2) 3N] Mo (CH3) and [(R3SiNCH2CH2) 3N] Mo (C= CR")(R3Si= Me3Si, PhMe2Si, or Ph2MeSi; R"= Me, Ph, or SiMe3) complexes could be prepared readily from [(R3SiNCH2CH2) 3N]-MoCl. 1 We have now found that attempted syntheses of [(R'NCH2CH2) 3N] W (alkyl) complexes usually yield alkylidyne complexes, even when ß protons are present in the alkyl. The monochloride complexes [(R3SiNCH2CH2) 3N] WCl (R3-Si= Me3Si, Me2PhSi, or MePh2Si) can be prepared in low yields (~ 20%) in THF from WCL (1, 2-dimethoxyethane) or WCl4 (TOF) 2 and the trilithium salts of the ligands,(R3-SiNLiCH2CH2) 3N.(See supplementary material for details.) Addition of methyllithium to [(Me3SiNCH2CH2) 3N] WCl in ether yields paramagnetic [(Me3SiNCH2CH2) 3N] W (CH3) in high yield. By the Evan’s method the magnetic moment was found to be 2.5 pb at 25 C, slightly less than the expected spin-only value (2.83 ps) for two unpaired electrons. Two characteristic ligand methylene resonances can be observed in CeDe at—31.43 (width at half-height= wi/2= 40 Hz) and—72.70 ppm (wi/2= 23 Hz) at 25 C, while the TMS methyl resonances are observed at 9.89 ppm. The CH3 resonance cannot be observed, although the CD3 resonance in [(Me3SiNCH2CH2) 3N] W (CD3) is observed at 7.5 ppm (wi/2= 5 Hz) in the 2H NMR spectrum. 4-6 [(Me3-SiNCH2CH2) 3N] W (CH3) is converted virtually quantitatively into [(Me3SiNCH2CH2) 3N] W= CH (d (CK)= 272.6 ppm, JCw= 244 Hz,()= 7.08 ppm, Jhw= 81 Hz)(eq 1) between 25 and 80 C. The reaction is first order through several half-lives and independent of concentration over a 5-fold range (Table 1) as determined by proton NMR at 500 MHz by following the decrease in the intensity of the TMS resonance. A resonance for molecular hydrogen can be observed, although dihydrogen’s low solubility in toluene-ág does not allow the amount to be quantified by NMR. From the data presented in Table 1, values for AH*= 19.2 kcal mol-1 and AS*=—16 eu