N,N-Dimethylbenzylamine, alkyl and aryl imines derived from benzaldehyde, and 2-phenyl-4,4-dimethyloxazoline all undergo cyclometallation with [IrCl 2 Cp*] 2 (Cp* = η-C 5 Me 5 ) when treated with NaOAc in dichloromethane at room temperature. The imines are also cyclometallated by [RhCl 2 Cp*] 2 under the same conditions whilst only N-alkyl imines are cyclometallated by [RuCl 2 (p-cymene)] 2 . The role of acetate in the cyclometallation is more than just as a base. X-Ray structures of cyclometallated complexes [MCl{C 6 H 4 -2-C(H)᎐ ᎐ NCH 2 CH 2 OMe-κC,N}(η-ring)](M = Ir, Rh ring = Cp*; M = Ru, ring = p-cymene), [MCl{C 6 H 4 -2-C(H)᎐ ᎐ NCH 2 CH 2 OMe-κC,N}Cp*](M = Ir, Rh), [RuCl(η 2 -O 2 CMe)(p-cymene)] and [IrCl 2 (NH 2 Ph)Cp*] are reported.

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Two new bulky aryl-bridged pyridyl-imine compartmental (pro)ligands, 2,6-{(2,6-i-Pr(2)C6H3)N=C(Me)C5H3N}2C6H3Y (Y = H L1, OH L2-H), have been prepared in moderate to good overall yields via a Stille-type cross-coupling approach. The molecular structure of L2-H reveals a transoid configuration within the pyridyl-imine units with a hydrogen-bonding interaction maintaining the phenol coplanar with one of the adjacent pyridine rings. The interaction of 2 equiv of MX2 with L1 in n-BuOH at 110 degrees C gives the binuclear complexes, [(L1)M2X4] (M = Fe, X = Cl (1a); M = Co, X = Cl (1b); M = Ni, X = Br (1c); M = Zn, X = Cl (1d)), in which the metal centers adopt distorted tetrahedral geometries and occupy the two pyridyl-imine cavities in L1. In contrast, deprotonation of L2-H occurs upon reaction with 2 equiv of MX2 to afford the phenolate-bridged species [(L2)M2(mu-X)X2] (M = Fe, X = Cl (2a); M = Co, X = Cl (2b); M = Ni, X = Br (2c); M = Zn, X = Cl (2d)). 1H NMR studies of diamagnetic 1d and 2d reveal that the limited rotation of the N-aryl groups in 1d is further impeded in 2d by steric interactions imparted by the two closely located N-aryl groups. Partial displacement of the bridging bromide in 2c results upon its treatment with acetonitrile to afford [(L2)Ni2Br3(NCMe)] [2c(MeCN)]; no such reaction occurs for 2a, 2b, or 2d. Upon activation with excess methylalumoxane (MAO), 1b, 1c, 2b, and 2c show some activity for alkene oligomerization forming low molecular-weight materials with methyl-branched products predominating for the nickel systems. Single-crystal X-ray diffraction studies have been performed on L2-H, 1c, 2b, 2c, 2c(NCMe), and 2d.

Reaction of a pyrrole imine with [IrCl 2 Cp*] 2 /NaOAc leads to N-H actiVation in preference to C-H actiVation at the pyrrole; howeVer, with the N-methylated ligand C-H actiVation occurs. Density functional calculations show that N-H bond actiVation is both kinetically and thermodynamically preferred to C-H actiVation. Both reactions occur with relatiVely low energy barriers by an electrophilic agostic interaction with the metal with simultaneous intramolecular hydrogen bonding with acetate leading to deprotonation Via a six-membered transition state.