Iridium(I) Hydroxides: Powerful Synthons for Bond Activation

Abstract

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.

The Mechanism of CO2 Insertion into Iridium(I) Hydroxide and Alkoxide Bonds: A Kinetics and Computational Study

“…Having developed a mechanistic understanding of the reaction between CO 2 and 1 , we investigated the reaction between CO 2 and an iridium hydroxide bearing a more bulky NHC ligand to determine if the procedure was general. Hence [Ir(cod)(IPr)(OH)] ( 9 )18 (IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) was reacted with CO 2 (1 atm), following the reported procedure14 (Scheme ). Analysis by 13 C{ 1 H} NMR spectroscopy indicated that a carbonate complex had indeed formed, with a quaternary carbon resonating at 164.6 ppm (see the Supporting Information).…”

Mechanism of CO2 Fixation by IrI–X Bonds (X = OH, OR, N, C)

“…[7,8] Any new organometallic complex or chemical mechanism that is able to perform or explain the capture of CO 2 is extremely interesting. [9,10] Very recently, a new Ir I complex, [11] [Ir(cod)(IiPr)(OH)] (1; cod = 1,5-cyclooctadiene; IiPr = 1,3-diisopropylimidazol-2-ylidene), was shown to fix CO 2 both in solution and in the solid state to form a dimeric structure (2) of 16-electron fourcoordinate and 18-electron five-coordinate Ir centers (see Scheme 1). [12] Furthermore, the modification of 1 by reaction with alcohols or primary amines allows the formation of its derivatives containing Ir-heteroatom bonds; for ex-4653 ditionally, in agreement with the experimental results, our results show that CO 2 insertion into the Ir-OR 1 (R 1 = H, methyl, and phenyl) and Ir-N bonds is kinetically facile, and the calculated activation energies span a range of only 12.0-23.0 kcal/mol.…”

Fluoride, bifluoride and trifluoromethyl complexes of iridium(i) and rhodium(i)

“…2 [Rh(cod)(NHC)(OH)] complexes were prepared according to reported procedures. 3 Method A: A vial was charged with [Ir(cod)(IPr)(Cl)] (50 mg, 0.071 mmol) and AgF (43.8 mg, 0.35 mmol) in CH 2 Cl 2 (1 mL) and the reaction mixture was stirred at rt in the S3 dark for 16 h. Once complete, pentane (1 mL) was added to the mixture and left to stand for 10 mins.…”