Iridium alkynyl complexes

Anti-Markovnikov hydration, and iridium alkynyl complexes,... 

Dinuclear iridium alkynyl complexes, synthesis and characteristics, 7, 331... 

Iridium alkynyl complexes are involved in the catalytic hydrosilylation of Esteruelas... 

The main species in solution has been identified to be the hydrido-alkynyl complex [IrH(C2Ph)(cod)(//2-iPrPCH2CH2OMe)]+BF4 (23). This is, however, only a sink that results from direct reaction of 22 with the 1-alkyne, draining the active catalyst from the system. The catalysis proceeds via the dihydrido-diene intermediate [IrH2(cod)(//2- PrPCH2CH2OMe)]+ BF4 (24), which reacts reversibly with the alkyne to yield the hydrido-iridium-styryl complex 25, followed by a rate-determining reaction of this hydrido-vinyl species with hydrogen to re-... 

Attempts to turn this acetylene dimerization reachon into a catalyhc polymeriza-hon process have failed thus far. In the presence of excess phenylacetylene, the iridium(I) complex 23 activates another Caikynyi—H bond and hansforms, after a hydrogen shift, to the stable (vinyl)(alkynyl) iridium(III) system 27 (Equahon 12.10). 

Since it is known that halo(phenyl)acetylenes add oxidatively to Vaska s complex to give (7-phenylethynyl iridium(III) halides, 32112, the intervention of phenyliodonium iridium(III) and rhodium(III) intermediates, 33, in the alkynyliodonium reactions seems plausible. In any case, the production of cr-alkynyl complexes with alkynyl(phenyl)-iodonium triflates appears to be both more general and efficient21. 

No relevant iridium alkynyls exist to date. However, the rhodium complexes Tp RhH(C = CPh)(PR3) (R = C6H5 (559), C6H4F-4 (560)) have been prepared by the addition of phenylacetylene to the respective bis(phosphine) complexes, and the ethyl propiolate complex Tp RhH(C = CC02Et)(PPh3) (561) has very recently been prepared in the same way. ... 

The copper-catalyzed reaction of j8-styrylboronic acid with sodium azide afforded ( )-j8-styryl azide in good yield. In rare cases, the rearrangement of butatrienylidene and alkynyl complexes of iridium led to special enazides. A single example of the formation of an alkenyl azide via palladium-catalyzed cyclization of an allenic substrate has also been reported. ... 

Reaction of [Ir(OMe)(PR3)(diene)] (R = Pr 3, Cy diene = COD, TFB 586) with HC=CCPh20H results in the formation of the alkynyl complexes [Ir(C CCPh20H)(PR3)(diene)] 587 which yield the iridium allenylidenes [Ir(C=C=CPh2)(PR3)(diene)] 588 after reaction with HBF-OEt2 (Scheme 84). ... 

Dinuclear Pt-Rh (336a-c, 339) and Pt-Ir (337a-c, 338) complexes with doubly alkynyl bridging systems have been isolated from the reactions between platinum alkynyl complex, 40 and from cyclooctadiene complexes of rhodium and iridium (Scheme 91). ... 

Ogo S, Uehara K, Abura T, Watanabe Y, Fukuzumi S (2004) pH-Selective synthesis and structures of alkynyl, acyl, and ketonyl intermediates in anti-Markovnikov and Markovnikov hydrations of a terminal alkyne with a water-soluble iridium aqua complex in water. J Am ChemSoc 126 16520-16527... 

A plausible reaction pathway was suggested by an experiment using labels, where the reaction proceeded via the pathway shown in Scheme 10.1. First, the oxidative addition of terminal alkyne 8 to an iridium complex leads to an alkynyl-... 

The transformation predominates in Group 9 (Rh, Ir) chemistry. Reactions of RhCl(L)2 2 with 1-alkynes give the q -alkyne complexes which slowly convert to the hydrido(alkynyl)s at room temperature. The latter are sensitive to air and not often isolated. Addition of pyridine affords RhHCl(C=CR)(py)(L)2, which readily lose pyridine in hydrocarbon solvents to give square-planar fran.s-RhCl(=C=CHR)(L)2. Alternatively, the Cp complexes Rh(=C=CHR)(L)Cp can be obtained by reaction of the chloro complexes vdth TlCp. In the iridium series, heating for 36h in refluxing toluene afforded the vinylidenes in 80-90% yields. Table 1.2 lists several examples of reactions in which the q -alkyne complexes have been detected. 

Mel, in Rh-catalyzed methanol carbonylation, 7, 256 to monocarbonyl iridium complexes, 7, 284 in mononuclear ruthenium and osmium alkynyl formations,... 

Vaska s complex, the square planar iridium(I) compound shown in equation 145, readily interacts with alkynyl(phenyl)iodonium triflates in toluene at room temperature21. Such reactions proceed with loss of iodobenzene and deliver octahedral Ir(III) complexes possessing (7-alkynyl and trifluoromethanesulfonato ligands in a Jnms-relationship. The rhodium(I) analog of Vaska s complex behaves in a similar way21. 

The lower reactivity of iridium complexes requires the use of more activated precursors. Thus, the neutral square-planar derivatives Zra .v- IrCI =C=C=C(R)Ph (Pz -Prs)2] (R = Ph, f-Bu) have been prepared from [IrH2Cl(Pz-Pr3)2] and the appropriate alkynol, via UV-promoted or CF3CO2H-catalyzed dehydration of the initially formed hydride-alkynyl intermediates [IrHCl C=CC(R)Ph(OH) (Pz-Pr3)2] [78, 81]. The cationic species [Ir(=C=C=CPh2)(/ -diene)( PR3) [BF4] (diene = COD, PR3 = PCys diene - TFB, PR3 - PCys, P/-Prs) are also known [211], They were synthesized by reacting the methoxo compounds [Ir(OMe)(z/ -diene)(PRs) with l,l-diphenyl-2-propyn-l-ol, followed by dehydration of the resulting alkynyl derivatives [Ir C=CCPh2(OH) (77 -diene)(PRs)] with stoichiometric amounts of HBF4. 

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