[Ru­(Cp)­(PPh 2NBn 2)­(MeCN)]­PF6 (1; PPh 2NBn 2 = 1,5-benzyl-3,7-phenyl-1,5-diaza-3,7-diphosphacyclooctane) and [Ru­(Cp)­(dppp)­(MeCN)]­PF6 (2; dppp = 1,3-bis­(diphenylphosphino)­propane) are both active toward the acceptorless dehydrogenation of benzylamine (BnNH2) and N-heterocycles. The two catalysts have similar activities but different selectivities for dehydrogenation products. Independent synthesis of a [Ru­(Cp)­(PPh 2NBn 2)­(NH2Bn)]­PF6 adduct (3) reveals the presence of a hydrogen bond between the bound amine and the pendent base of the PPh 2NBn 2 ligand. Preliminary mechanistic studies reveal that the benzylamine adduct is not an on-cycle catalyst intermediate.

The first successful use of the PN (1,5-R'-3,7-R-1,5-diaza-3,7-diphosphacyclooctane) ligand family toward an organic synthesis is described. The precatalysts [Ru(Cp)(PN)(MeCN)]PF are active toward cyclization of 2-ethynylbenzyl alcohol at low catalyst loading and mild temperatures. Catalyst performance however is limited by both low conscription and by competitive deactivation.

A highly tunable phosphine-imine ligand family is introduced. Following metallation with ruthenium, deprotonation of the ligand affords a phosphine-enamido species. Complexes with the ligand in both the imine and enamido forms are active toward acceptorless dehydrogenation reactions.

The synthesis of three new NiCl(allyl/cinnamyl)(NHC) complexes, containing a bifunctional NHC (N-heterocyclic carbene) ligand is described. Two different NHCs were utilized that contain a secondary amine (HNR; R = t-Bu or Mes) moiety on one of the N-imidazolylidene arms. Complexes with allyl (2 a) and cinnamyl (3 a and 3 b) were each crystallographically characterized and h 3 -allyl and k 1 -C NHC ligand coordination modes were found in the solid-state. In the solution-state, each of the ligands shows highly fluxional behaviour. Halide substitution of the chloro ligand for iodo effectively slows the ligand dynamics and permits solution-state characterization that is in agreement with the solid-state structures. The complexes react with oxygen to ultimately oxidize the allyl or cinnamyl ligands to acrolein (AC) or cinnamaldehyde (CA) and phenyl vinyl ketone (PVK), respectively. The bifunctional nature of the NHC has limited influence on oxidation reactivity, but preliminary evidence suggests it plays a role in the stability of the nickel oxidation products.[a] R.