Computational Study of the C - and N -Bound Tautomers of [Ru(Cl)(H)(CO)-(PPh 3 ) 2 (I i PrMe 2 )] (I i PrMe 2 = 3-Isopropyl-4,5-dimethylimidazol-2-ylidene)
Computational Study of the C - and N -Bound Tautomers of [Ru(Cl)(H)(CO)-(PPh 3 ) 2 (I i PrMe 2 )] (I i PrMe 2 = 3-Isopropyl-4,5-dimethylimidazol-2-ylidene)
复制标题
[Ru(Cl)(H)(CO)-(PPh 3 ) 2 (I i PrMe 2 )] (I i PrMe 2 = 3-异丙基-4,5-) C 和 N 结合互变异构体的计算研究
DOI：
10.1002/ejic.200801228
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发表时间：
2009
影响因子：
2.3
通讯作者：
Häller L
中科院分区：
文献类型：
--
作者：
Häller L
密度泛函理论计算被用于研究Whittlesey和同事（J. Am.）报道的[Ru(Cl)(H)(CO)(PPh3)2(IiPrMe2)] （IiPrMe2= 3‐异丙基‐4,5‐二甲基咪唑‐2‐乙基）的c -结合(2)和n -结合(3)互变异构体相对能量的控制因素。化学。Soc.2006、128、13702)。计算表明，theN束缚形式更稳定。进一步分析表明，CO配体转移到C/N结合位点是决定theN结合形式更大稳定性的关键因素。N3位置上的巨大的ipr取代基进一步增强了这种偏好。计算预测，c -结合的互变异构体将有利于具有庞大的C5取代基的NHC配体与N3和C4上的小基团结合。因此，[Ru(Cl)(H)(CO)(PPh3)2(NHC)]配合物中NHC = 5‐R‐R‐咪唑‐2‐乙基烯或3‐Me‐5‐R‐咪唑‐2‐乙基烯（R =tBu, Ph）被预测为更稳定的碳结合形式。从2和3中失去CO或Cl配体形成的五坐标方形锥体物种显示出对c结合形式的偏好增加。事实上，当C/N结合位点转移到空位点时，C结合的互变异构体成为更稳定的物种。（©Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009）
Density functional theory calculations have been used to study the factors controlling the relative energies of theC‐bound (2) andN‐bound (3) tautomers of [Ru(Cl)(H)(CO)(PPh3)2(IiPrMe2)] (IiPrMe2= 3‐isopropyl‐4,5‐dimethylimidazol‐2‐ylidene) reported by Whittlesey and co‐workers (J. Am. Chem. Soc.2006,128, 13702). The calculations indicate that theN‐bound form is more stable. Further analysis reveals the presence of a CO ligandtransto the C/N binding site is a key factor in determining the greater stability of theN‐bound form. This preference is further enhanced by the bulkyiPr substituent at the N3 position. The calculations predict that theC‐bound tautomer will be favoured with NHC ligands that feature a bulky C5 substituent in combination with small groups at N3 and C4. Thus [Ru(Cl)(H)(CO)(PPh3)2(NHC)] complexes where NHC = 5‐R‐imidazol‐2‐ylidene or 3‐Me‐5‐R‐imidazol‐2‐ylidene (R =tBu, Ph) are predicted to be more stable as theC‐bound form. Five‐coordinate square‐pyramidal species formed by loss of a CO or Cl ligand from2and3show an increased preference for theC‐bound form. Indeed, when the C/N binding site istransto a vacant site theC‐bound tautomer becomes the more stable species.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)