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.

A series of chiral bipyridine-type ligands 5-12 has been synthesized via a de novo construction of the pyridine nucleus. The chiral moieties of the ligands originate from the monoterpene realm, namely, pinocarvone (13 f 6, 7, and 9), myrtenal (18 f 5), nopinone (21 f 8 and 10), and menthone (28 f 11 and 12); the first three precursors can be obtained in one step from -and R-pinene, respectively. Complexes of these ligands with molybdenum(0) (38-40) and copper(II) (41) have been characterized by single-crystal X-ray crystallography. While complex 38 exhibits polymorphism (monoclinic and tetragonal forms crystallize from the same batch), 41 is characterized by a tetrahedrally distorted geometry of the metal coordination. The Mo and Pd complexes exhibit modest asymmetric induction in allylic substitution (43 f 44), and the Cu(I) counterpart of 41, derived from 10 (PINDY) and Cu(OTf) 2 , shows promising enantioselectivity (49-75% ee) and reaction rate (g30 min at room temperature) in allylic oxidation of cyclic olefins (47 f 48). The Cu(I) complex of 11 (MINDY) proved effective in cyclopropanation (49 f 50) with up to 72% ee.

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.

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The ligand 4,4-dimethyl-2-oxazolinylbenzene is easily cyclometalated by [IrCl 2 Cp*] 2 or [RuCl-(MeCN) 2 (p-cymene)]PF 6 in the presence of sodium acetate. In the case of iridium the resultant complex dissolves in acetonitrile in the presence of KPF 6 to give an acetonitrile-coordinated cationic complex. The analogous complex is formed directly in the ruthenium cyclometalation reaction. These labile cationic complexes undergo insertion reactions with internal and terminal alkynes. Internal alkynes give only monoinsertion products, whereas terminal alkynes give mono-or di-insertion products. The cations will also react with CO, but no insertion occurs in this case.