A Domino Fusion of an Organic Ligand Depended on Metal‐Induced and Oxygen Insertion, Unraveled by Crystallography, Mass Spectrometry, and DFT Calculations

• Published in: Chemistry : a European journal Vol. 27; no. 8; pp. 2875 - 2881
• Main Authors: Chen, Jin‐Ming, Peng, Liang, Zhou, Fu‐Fang, Liu, Bin, Hou, Cheng, Li, Jia‐Wei, Huang, Zhou, Kurmoo, Mohamedally, Zeng, Ming‐Hua
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 05.02.2021
• Subjects: Carbonyl compounds; Carbonyls; Chemistry; cobalt-mediated reactions; Crystallization; Crystallography; Crystals; ESI-MS; Ferric chloride; Imidazole; in situ reactions; Iron chlorides; Mass spectrometry; Mass spectroscopy; Mathematical analysis; Metals; Oxidation; Oxygen; Oxygen atoms; Pyrazine; Scientific imaging; Spectroscopy; tetrasubstituted pyrazine; ESI-MS; cobalt-mediated reactions; crystallography; in situ reactions; tetrasubstituted pyrazine
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202004396

Herein, the reaction of (1‐methyl‐1 H‐benzo[d]imidazol‐2‐yl)methanamine (L1) with Co(H2O)6Cl2, in CH3CN at 120 °C, leading to the 2,3,5,6‐tetrakis(1‐methyl‐1 H‐benzo[d]imidazol‐2‐yl)pyrazine (3), isolated as a dimeric cluster {[CoII2(3)Cl4]⋅2 CH3CN} (2), is reported. When O2 and H2O are present, (1‐methyl‐1 H‐benzo[d]imidazole‐2‐carbonyl)amide (HL1′) is first formed and crystallized as [CoIII(L1)2(L1′)]Cl2⋅2 H2O (4) before fusion of HL1′ with L1, giving 1‐methyl‐N‐(1‐methyl‐1 H‐benzo[d]imidazol‐2‐carbonyl)‐1 H‐benzo[d]imidazol‐2‐carboxamide (HL2′′) forming a one‐dimensional (1D) chain of [CoII3(L2′′)2Cl4]n (5). The combination of crystallography and mass spectrometry (ESI‐MS) of isolated crystals and the solutions taken from the reaction as a function time reveal seven intermediate steps leading to 2, but six steps for 5, for which a different sequence takes place. Control and isotope labeling experiments confirm the two carbonyl oxygen atoms in 5 originate from both air and water. The dependence on the metals, compared with FeCl3⋅6 H2O leading to a stable triheteroarylmethyl radical, is quite astounding, which could be attributed to the different oxidation states of the metals and coordination modes confirmed by DFT calculations. This metal and valence dependent process is a very useful way for selectively obtaining these large molecules, which are unachievable by common organic synthesis. Dominoes under investigation: Tandem application of crystallography and mass spectrometry unraveled a competitive in situ domino solvothermal reaction to tetrabenzimidazol‐pyrazine within [Co2(3)Cl4] in seven steps and to a deprotonated imide anion L2′′ within 1D chain ([Co1.5(L2′′)]n) in six steps.