Metal-Templated Hydrogen Bond Donors as 鈥淥rganocatalysts鈥?for Carbon鈥揅arbon Bond Forming Reactions: Syntheses, Structures, and Reactivities of 2-Guanidinobenzimidazole Cyclopentadienyl Ruthenium Compl

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• 作者：Alexander Scherer ; Tathagata Mukherjee ; Frank Hampel ; John A. Gladysz
• 刊名：Organometallics
• 出版年：2014
• 出版时间：December 8, 2014
• 年：2014
• 卷：33
• 期：23
• 页码：6709-6722
• 全文大小：728K
• ISSN：1520-6041

文摘

The reaction of 2-guanidinobenzimidazole (GBI) and (畏⁵-C₅H₅)Ru(PPh₃)₂(Cl) in refluxing toluene gives the chelate [(畏⁵-C₅H₅)Ru(PPh₃)(GBI)]⁺Cl^{鈥?/sup> (1+Cl鈥?/sup>; 96%). Subsequent anion metatheses yield the BF₄鈥?/sup>, PF₆鈥?/sup>, and BAr_f鈥?/sup> (B(3,5-C₆H₃(CF₃)₂)₄鈥?/sup>) salts (77鈥?5%). Reactions with CO give the carbonyl complexes [(畏5-C₅H₅)Ru(CO)(GBI)]+X鈥?/sup> (2+X鈥?/sup>; X鈥?/sup> = Cl鈥?/sup>, BF₄鈥?/sup>, PF₆鈥?/sup>, BAr_f鈥?/sup>; 87鈥?2%). The last three salts can also be obtained by anion metatheses of 2+Cl鈥?/sup> (77鈥?7%), as can one with the chiral enantiopure anion P(o-C₆Cl₄O₂)₃鈥?/sup> ((螖)-TRISPHAT鈥?/sup>; 81%). The reaction of [(畏5-C₅H₅)Ru(CO)(NCCH₃)₂]+PF₆鈥?/sup> and GBI also gives 2+PF₆鈥?/sup> (81%). The pentamethylcyclopentadienyl analogues [(畏5-C₅Me₅)Ru(CO)(GBI)]+X鈥?/sup> (3+X鈥?/sup>; X鈥?/sup> = Cl鈥?/sup>, BF₄鈥?/sup>, PF₆鈥?/sup>, BAr_f鈥?/sup>; 61鈥?4%) are prepared from (畏5-C₅Me₅)Ru(PPh₃)₂(Cl), GBI, and CO followed (for the last three) by anion metatheses. An indenyl complex [(畏5-C₉H₇)Ru(PPh₃)(GBI)]+Cl鈥?/sup> (96%) is prepared from (畏5-C₉H₇)Ru(PPh₃)₂(Cl) and GBI. All complexes are characterized by NMR (1H, 13C, 31P, 19F, 11B), with 2D spectra aiding assignments. Crystal structures of 1+PF₆鈥?/sup>路CH₂Cl₂ and 1+BAr_f鈥?/sup>路CH₂Cl₂ are determined; the anion is hydrogen bonded to the cation in the former. Complexes 1鈥?b>3+X鈥?/sup> are evaluated as catalysts (10 mol %, RT) for condensations of indoles and trans-尾-nitrostyrene. The chloride salts are ineffective (0鈥?% yields, 48鈥?0 h), but the BAr_f鈥?/sup> salts exhibit excellent reactivities (97鈥?6% yields, 1鈥?8 h), with the BF₄鈥?/sup> and PF₆鈥?/sup> salts intermediate. Evidence for hydrogen bonding of the nitro group to the GBI ligand is presented. GBI shows no catalytic activity; a BAr_f鈥?/sup> salt of methylated GBI is active, but much less so than 2鈥?b>3+BAr_f鈥?/sup>.}