Stoichiometric C−C Coupling Reactions in the Coordination Sphere of an Iridium(III) Alkyl

Abstract

An alkyl hydride η 1 -acetone complex of iridium or its R-elimination product undergoes insertion into alkenes to give a carbene dihydride via a proposed pathway that involves C-C bond formation by a rare C(sp 3 )-C(sp 3 ) reductive elimination followed by a double C-H activation. In MeCN solution, reversible R-elimination equilibrates this carbene dihydride insertion product with its MeCN adduct, an iridium alkyl hydride with diastereotopic trans triphenylphosphine ligands ( 2 J PP ) 382 Hz). Alkynes also react, but they give a coupled η 3 -allyl complex via a proposed pathway that involves C-C bond formation by C(sp 3 )-C(sp 2 ) reductive elimination. Crystal structures of key products are reported.

Transition Metal Catalyzed CarbonCarbon Bond Formation: The Key of Homogeneous Catalysis

“…There are some other studies of CaC reductive elimination reactions performed for different metals, which are in line with calculated reactivity patterns [93][94][95].…”

Extending the NHC Concept: C–C Coupling Catalysis by a PdII Carbene (rNHC) Complex with Remote Heteroatoms

“…[8] Recent successes include the use of N-heterocyclic carbenes (NHC's) as ligands in the precursor complexes. [9][10][11] Very few N-heterocyclic-coordinated carbene ligands with remote heteroatoms (rNHC's) are known [12] (related, but without remote heteroatoms are α-N carbenes derived from pyridine [13] or azoles [14] ). The recent discovery of the exceptional stability and complex dynamics of such Pd II and Pt II compounds [15] encouraged a study to establish their potential use as precatalysts in coupling reactions.…”

The formation of aldehydes from the photochemically activated reaction of Cp*Ir(CO)(Cl)(CH2R) complexes with water

“…Transition metal alkyl complexes are also known to decompose via α-H elimination and abstraction, but this mode of decomposition is generally not common for late transition metal complexes. In the case of iridium complexes, there are very few reports of α-H elimination and, in general, they appear to occur for sterically encumbered iridium centers [2,3,4,5].…”

“…The dimeric iridium complex [Cp*IrCl 2 ] 2 (1) reacts with terminal alkynes (2) in the presence of water to form the alkyl carbonyl complexes Cp*Ir(CO)(Cl)(CH 2 R) (3) via a C≡C bond cleavage reaction (Scheme 1). This reaction proceeds with a variety of aromatic and aliphatic alkynes, and the possible reaction pathway has been studied experimentally and computationally [1].…”