American Chemical Society
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Diamino- and Mixed Amino–Amido-N-Heterocyclic Carbenes Based on Triazine Backbones

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posted on 2012-03-12, 00:00 authored by Abdelaziz Makhloufi, Walter Frank, Christian Ganter
The synthesis of novel hexahydrotriazine-based NHCs from easily available starting materials is described. Tribenzyltriazacyclohexane 1 is converted stepwise to the six-membered diamino carbene 3 with a saturated ring structure. Analogously, the cyclic mixed amino–amido carbene 12 is obtained starting from a cyclic urea derivative. Both carbenes were characterized by trapping reactions with sulfur and selenium as well by the preparation of metal complexes of the type (COD)­MX-NHC (M = Rh, Ir; COD = 1,5-cyclooctadiene), which were converted to the respective dicarbonyl complexes (CO)2MX-NHC. IR spectra of the carbonyl derivatives allowed the Tolman electronic parameter to be determined for carbenes 3 (2052 cm–1) and 12 (2058 cm–1) and revealed a shift of 6 cm–1 due to the presence of one amide function. X-ray structure determinations are reported for an amidinium species, a carbene sulfide, and the (COD)­RhBr complex of the amino–amido carbene 12.