A family of iridium(I) hydroxides of the form [Ir(cod)(NHC)(OH)] (cod = 1,5-cyclooctadiene, NHC = N-heterocyclic carbene) is reported. Single-crystal X-ray analyses and computational methods were used to explore the structural characteristics and steric properties of these new complexes. The model complex [Ir(cod)(IiPr)(OH)] (IiPr = 1,3-(diisopropyl)imidazol-2-ylidene) undergoes reaction with a wide variety of substrates including boronic acids and silicon compounds. In addition, O-H, N-H and C-H bond activation was achieved with alcohols, carboxylic acids, amines and various sp-, sp(2)- and sp(3)-hybridised carbon centres, giving access to a wide range of new Ir(I) complexes. These studies have allowed us to explore the exciting reactivity of this motif, revealing a versatile and useful synthon capable of activating important chemical bonds under mild (typically room temperature) conditions. No additives were required and, in the case of X-H bond activation, water was the only waste product, rendering this an atom efficient procedure for bond activation. This system has great potential for the construction of new catalytic cycles for organic synthesis and small-molecule activation.

E/Z-Selectivity in Ruthenium-Mediated Cross Metathesis. -A detailed investigation on the influence of the ancillary ligand on the activity of Ru/NHC indenylidene complexes in cross metathesis reactions (CM) is presented. In general CM leads to good initial Z-selectivity. Due to secondary metathesis reactions the thermodynamically more stable E-isomer is formed subsequently. Very active precatalysts like (Ib,c) achieve very good conversions in short reaction times, but they also promote fast isomerization of the Z-isomer. Good Z-selectivity at long reaction times is obtained using complexes bearing less labile NHC leaving groups, e.g. (II). -(LUJAN, C.; NOLAN*, S. P.; Catal.

Pre-formed transition metal-NHC complex is shown to be an effective catalyst for Atom Transfer Radical Cyclisation (ATRC) reactions.

Substrate-controlled titanium-mediated aldol reactions from (S)-4-benzyloxy-3-methyl-2-butanone provide satisfactory levels of 2,5-syn asymmetric induction if they are carried out in the presence of a second equivalent of TiCl(4). Such reactions give high yields and excellent diastereoselectivity with a wide array of achiral and chiral aldehydes without needing other sources of chirality. This procedure is thus of interest for the synthesis of natural products. Furthermore, spectroscopic studies and analyses of the reacting species have revealed a possible mechanism to account for the experimental results.