Reaction of an (Alkyl)(alkenyl)(alkynyl)iridium(III) Complex with HCl:  Intramolecular C−C Bond Formation from Alkyl, Alkenyl, and Alkynyl Groups Coordinated to “Ir(CO)(PPh₃)₂”. H/D Exchange between CH₃ and DCl

Abstract

Reaction of the (alkyl)(alkenyl)(alkynyl)iridium(III) complex [Ir(CH3)(CHCHNEt3)(C⋮C(p-C6H4CH3))(CO)(PPh3)2]ClO4 (3) with aqueous HCl initiates an intramolecular coupling reaction between −CH3 and −C⋮C(p-C6H4CH3) groups to give [Ir(C(CH3)CH(p-C6H4CH3)(CHCHNEt3)(Cl)(CO)(PPh3)2]ClO4 (5), which further reacts with aqueous HCl to produce [Ir(CHCHNEt3)(Cl)2(CO)(PPh3)2]ClO4 (6) and cis-CH3CHCH(p-C6H4CH3) (7). Complex 5 yields the C−C coupling product [(p-C6H4CH3)HCC(CH3)CHCHNEt3]ClO4 (8) when it is refluxed in CHCl3. The (alkyl)bis(alkynyl)iridium(III) compound Ir(CH3)(C⋮C(p-C6H4CH3))2(CO)(PPh3)2 (4) reacts with aqueous HCl to give H2CCCH(p-C6H4CH3) (9). Complex 3 reacts with excess DCl to give the d 5 isotopomer CD3CDCD(p-C6H4CH3) (7- d 5 ), while the reaction of 4 with DCl gives the d 1 isotopomer H2CCCD(p-C6H4CH3) (9- d 1 ). Plausible reaction pathways are discussed for the formation of 7 and 9 and for the H/D exchange to give the isotopomer 7- d 5 .

C-C and C-O Coupling Reactions of Terminal Alkynes by a Water Soluble Organoiridium Electron-transfer Mediator in Thin Layer of Water on Gold Electrode

“…Terminal alkynes are known to coordinate toward metal center to give stable π-alkyne or σ-alkynyl compound [6][7][8][9][10]. In fact, it has been well-documented that metal vinylidene is obtained directly from the rearrangement of π-coordinated terminal alkynes [6][7][8][9][10][11][12][13][14][15][16][17][18][19]39,40]. It seems reasonable to include the direct attack of H 2 O on the carbon of the Ir-(HC≡CR) to produce ketones and on the α-carbon of the vinylidene moiety (Ir=C=CHR) to yield a hydroxyl carbene compounds followed by reductive elimination to give aldehydes.…”

“…The dimerization of alkynes catalyzed by a variety of transition metal compounds has been extensively studied and suggested the elaborated mechanism [11][12][13][14][15][16][17][18]. The key step of alkyne coupling reaction has been commonly proposed to involve the rearrangement of metal π-alkyne to metal vinylidene form [11][12][13][14][15][16][17][18].…”

“…This resulting anionic radical compound could produce highly reactive species which will be used to catalyze the activation of organic substrates such as alkynes. Metal-catalyzed hydration and oligomerization of alkynes provide important processes in organic chemistry to aldehydes, ketones, and conjugated olefin compounds since they are the carbon-oxygen [6][7][8][9][10] and -carbon [11][12][13][14][15][16][17][18][19] bond forming reactions which produce a variety of new inexpensive starting materials.…”

“…Among water-soluble ligands, PAr 3 (P(m-C 6 H 4 SO 3 Na) 3 ) is the most commonly used ligand to prepare water-soluble metal compounds [27][28][29][30][31][32]. Iridium-Cp * (C 5 Me 5 -) compounds have been investigated and have drawn much attention due to their diverse and interesting reactivity with alkynes [11][12][13][14][15][16][17][18][27][28][29][30][31][32][33][34][35][36][37].…”

“…Since it is well-known that terminal alkynes can be activated by organoiridium compounds [11][12][13][14][15][16][17][18], this voltammetric observation prompted us to look into details of reduced-metal catalyzed activation of alkynes in biphasic (H 2 O/CH 2 ClCH 2 Cl) solution. The biphasic…”