Dihydroperimidine-Derived N‑Heterocyclic Pincer Carbene Complexes via Double C–H Activation
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The reactions of 1,8-diaminonaphthalene with paraformaldehyde and secondary phosphines (HPR2, R = Ph, Cy) directly afford N,N′-bis(phoshinomethyl)dihydroperimidines H2C(NCH2PR2)2C10H6 (R = Ph (1a), Cy (1b)), the methylene group of which undergoes chelate-assisted double C–H activation with [RhCl(PPh3)3] to afford dihydroperimidine-derived N-heterocyclic pincer carbene (per-NHC) complexes [RhCl{C(NCH2PR2)2C10H6}] (R = Ph (2a), Cy (2b)). Insight into the mechanism of these C–H activation processes is provided by the reaction of 1b with [IrCl(CO)(PPh3)2] to provide the dihydroperimidinyl-hydrido complex [IrHCl(CO){CH(NCH2PR2)2C10H6}] (3b), which in turn reacts with silver salts Ag[Y] to afford, via hydride abstraction and subsequent C–H activation, the per-NHC ligated salts [IrHCl(CO){C(NCH2PR2)2C10H6}] ([4b]Y, Y = PF6, SbF6, PO2F2).
