Alkaline-Earth Metal Mediated Benzene-to-Biphenyl Coupling |
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| Authors: | Jonathan Mai Michael Morasch Dr Dawid Jędrzkiewicz Dr Jens Langer Dr Bastian Rösch Prof Dr Sjoerd Harder |
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| Institution: | Inorganic and Organometallic Chemistry, Universität Erlangen-Nürnberg, Egerlandstrasse 1, 91058 Erlangen, Germany |
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| Abstract: | Complex (DIPePBDI)Ca]2(C6H6), with a C6H62− dianion bridging two Ca2+ ions, reacts with benzene to yield (DIPePBDI)Ca]2(biphenyl) with a bridging biphenyl2− dianion (DIPePBDI=HCC(Me)N-DIPeP]2; DIPeP=2,6-CH(Et)2-phenyl). The biphenyl complex was also prepared by reacting (DIPePBDI)Ca]2(C6H6) with biphenyl or by reduction of (DIPePBDI)CaI]2 with KC8 in presence of biphenyl. Benzene-benzene coupling was also observed when the deep purple product of ball-milling (DIPPBDI)CaI(THF)]2 with K/KI was extracted with benzene (DIPP=2,6-CH(Me)2-phenyl) giving crystalline (DIPPBDI)Ca(THF)]2(biphenyl) (52 % yield). Reduction of (DIPePBDI)SrI]2 with KC8 gave highly labile (DIPePBDI)Sr]2(C6H6) as a black powder (61 % yield) which reacts rapidly and selectively with benzene to (DIPePBDI)Sr]2(biphenyl). DFT calculations show that the most likely route for biphenyl formation is a pathway in which the C6H62− dianion attacks neutral benzene. This is facilitated by metal-benzene coordination. |
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| Keywords: | Alkaline-Earth Metal Cross-Coupling DFT Calculations Low-Valent Mechanochemistry |
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