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om2c00129_si_001.txt (45.58 kB)

Isomers of Molybdenum Imido Alkylidene N‑Heterocyclic Carbene Complexes

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posted on 2022-05-06, 19:05 authored by Iris Elser, Roman Schowner, Laura Stöhr, Katharina Herz, Mathis J. Benedikter, Suman Sen, Wolfgang Frey, Dongren Wang, Michael R. Buchmeiser
The library of molybdenum imido alkylidene N-heterocyclic carbene (NHC) complexes Mo­(N-G)­(CHCMe2R1)­(OTf)2(NHC) (G = 2,6-Me2-C6H3, 2,6-Cl2-C6H3, 2-CF3-C6H4, 2-tBu-C6H4, 2,6-iPr2-C6H3, tBu, adamantyl, 1-phenylcyclohexyl, 1-phenyl-3-methylcyclohexyl) was extended to complexes with unsymmetrical (4i) and chiral (4j) imido ligands. New 1,3-bis­(2,4,6-trimethylphenyl)­imidazol-2-ylidene (IMes, 4b−d, 4f,g, 4ik), 1,3-biscyclohexylimidazol-2-ylidene (ICy, 4h, 4l−n), and 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene (TPT, 4a, 4e, 4o) complexes were synthesized. Substitution of one triflate in the molybdenum imido alkylidene NHC bistriflate compounds with an alkoxide or a phenoxide afforded complexes Mo­(N-G)­(CHCMe2R1)­(OTf)­(OR2)­(NHC) (5ai) and was confirmed to proceed via a selective replacement of one specific triflate. The careful analysis of NMR and single-crystal X-ray data allowed for the determination of solution and solid-state structures. Cis- and trans-OTf isomers of IMes complexes with alkyl-substituted imido ligands, rotamers of TPT-ligated complexes, and syn-/anti-isomers and diastereomers were identified.