53470-69-2Relevant academic research and scientific papers
Mild, reversible reaction of iridium(III) amido complexes with carbon dioxide
Dobereiner, Graham E.,Wu, Jianguo,Manas, Michael G.,Schley, Nathan D.,Takase, Michael K.,Crabtree, Robert H.,Hazari, Nilay,Maseras, Feliu,Nova, Ainara
, p. 9683 - 9693 (2012/10/30)
Unlike some other Ir(III) hydrides, the aminopyridine complex [(2-NH 2-C5NH4)IrH3(PPh3) 2] (1-PPh3) does not insert CO2 into the Ir-H bond. Instead 1-PPh3 loses H2 to form the cyclometalated species [(κ2-N,N-2-NH-C5NH4)IrH 2(PPh3)2] (2-PPh3), which subsequently reacts with CO2 to form the carbamato species [(κ2-O,N-2-OC(O)NH-C5NH4)IrH 2(PPh3)2] (10-PPh3). To study the insertion of CO2 into the Ir-N bond of the cyclometalated species, a family of compounds of the type [(κ2-N,N-2-NR-C 5NH4)IrH2(PR′3)2] (R = H, R′ = Ph (2-PPh3); R = H, R′ = Cy (2-PCy 3); R = Me, R′ = Ph (4-PPh3); R = Ph, R′ = Ph (5-PPh3); R = Ph, R′ = Cy (5-PCy3)) and the pyrimidine complex [(κ2-N,N-2-NH-C4N 2H3)IrH2(PPh3)2] (6-PPh3) were prepared. The rate of CO2 insertion is faster for the more nucleophilic amides. DFT studies suggest that the mechanism of insertion involves initial nucleophilic attack of the nitrogen lone pair of the amide on CO2 to form an N-bound carbamato complex, followed by rearrangement to the O-bound species. CO2 insertion into 1-PPh 3 is reversible in the presence of H2 and treatment of 10-PPh3 with H2 regenerates 1-PPh3, along with Ir(PPh3)2H5.
Abnormal ligand binding and reversible ring hydrogenation in the reaction of imidazolium salts with IrH5(PPh3)2
Gruendemann, Stephan,Kovacevic, Anes,Albrecht, Martin,Faller, Jack W.,Crabtree, Robert H.
, p. 10473 - 10481 (2007/10/03)
We show that imidazolium salts do not always give normal or even aromatic carbenes on metalation, and the chemistry of these ligands can be much more complicated than previously thought. N,N′-disubstituted imidazolium salts of type [(2-py)(CH2)
Large effects of ion pairing and protonic-hydridic bonding on the stereochemistry and basicity of crown-, azacrown-, and cryptand-222-potassium salts of anionic tetrahydride complexes of iridium(III)
Landau, Shaun E.,Groh, Kai E.,Lough, Alan J.,Morris, Robert H.
, p. 2995 - 3007 (2008/10/08)
The compounds [K(Q)][IrH4(PR3)2] (Q = 18-crown-6, R = Ph, iPr, Cy; Q = aza-18-crown-6, R = iPr; Q = 1,10-diaza-18-crown-6, R = Ph, iPr, Cy; Q = cryptand-222, R = iPr, Cy) were formed in the reactions of IrH5-(PR3)2 with KH and Q. In solution, the stereochemistry of the salts of [IrH4(PR3)2]- is surprisingly sensitive to the countercation: either trans as the potassium cryptand-222 salts (R = Cy, iPr) or exclusively cis (R = Cy, Ph) as the crown- and azacrown-potassium salts or a mixture of cis and trans (R = iPr). There is IR evidence for protonichydridic bonding between the NH of the aza salts and the iridium hydride in solution. In single crystals of [K(18-crown-6)][cis-IrH4(PR3)2] (R = Ph, iPr) and [K(aza-18-crown-6)][cis-IrH4(Pi Pr3)2], the potassium bonds to three hydrides on a face of the iridium octahedron according to X-ray diffraction studies. Significantly, [K(1,10-diaza-18-crown-6)][transIrH4(Pi Pr3)2] crystallizes in a chain structure held together by protonic-hydridic bonds. In [K(1,10-diaza-18-crown-6)][cis-IrH4(PPh3)2], the potassium bonds to two hydrides so that one NH can form an intra-ion-pair protonichydridic hydrogen bond while the other forms an inter-ion-pair NH···Hlr hydrogen bond to form chains through the lattice. Thus, there is a competition between the potassium and NH groups in forming bonds with the hydrides on iridium. The more basic PiP3 complex has the lower N-H stretch in the IR spectrum because of stronger N-H···HIr hydrogen bonding. The trans complexes have very low Ir-H wavenumbers (1670-1680) due to the trans hydride ligands. The [K(cryptand)]+ salt of [trans-IrH4(PiPr3)2]- reacts with WH6(PMe2Ph)3 (pKαTHF 42) to give an equilibrium (Keq = 1.6) with IrH5(PiPr3)2 and [WH5(PMe2Ph)3]- while the same reaction of WH6(PMe2Ph)3 with the [K(18-crown-6)]+ salt of [cis-IrH4(PiPr3)2]- has a much larger equilibrium constant (Keq = 150) to give IrH5(Pi-Pr3)2 and [WH5(PMe2Ph)3]-; therefore, the tetrahydride anion displays an unprecedented increase (about 100-fold) in basicity with a change from [K(crypt)]+ to [K(crown)]+ countercation and a change from trans to cis stereochemistry. The acidity of the pentahydrides decrease in THF as IrH5(PiPr3)2/[K(crypt)] [trans-IrH4(PiPr3)2] (pKαTHF = 42) > IrH5-(PCy3)2/[K(crypt)][trans- IrH4(PCy3)2] (pKαTHF = 43) > IrH5(PiPr3)2/[K(crown)] [cis-IrH4(PiPr3)2] (pKαTHF = 44) > IrH5-(PCy3)2/[K(crown)][cis H4(PCy3)2]. The loss of PCy3 from IrH5(PCy3)2 can result in mixed ligand complexes and H/D exchange with deuterated solvents. Reductive cleavage of P-Ph bonds is observed in some preparations of the PPh3 complexes.
Synthesis and characterization of new hydridoiridium complexes containing carboxylate ligands
Esteruelas, Miguel A.,García, María P.,Lahoz, Fernando J.,Martín, Marta,Modrego, Javier,O?ate, Enrique,Oro, Luis A.
, p. 3473 - 3480 (2008/10/08)
The complexes IrH2(η2-O2CR)(PPh3)2 (R = (S)-CH(NaphOMe)Me (2), (R)-CH(OMe)Ph (3), (R)-C(CF3)(OMe)Ph (4), (S)-CHOC(=O)CH2CH2 (5)) have been prepared by reaction of IrH5(PPh3)2 (1) with the corresponding carboxylic acid RCO2H. The reactivity of these compounds toward acetylenedicarboxylic dimethyl ester and HBF4 has been studied. 2-5 react with acetylenedicarboxylic dimethyl ester to afford the hydrido-vinyl complexes IrH-{C(CO2Me)=CH(CO2Me)}(η2-O 2CR)(PPh3)2 (R = (S)-CH(NaphOMe)Me (6), (R)-CH(OMe)Ph (7), (R)-C(CF3)(OMe)Ph (8), (S)-CHOC(=O)CH2CH2 (9)) by insertion of the alkyne into one of the two Ir-H bonds of the starting complexes. Reactions of 2 and 3 with HBF4 in diethyl ether lead to the hydrido-bridged dinuclear complexes [Ir2H2(PPh3)4(μ-H)2 (μ-η2-O2CR)]BF4 (R = (S)-CH(NaphOMe)Me (10), (R)-CH(OMe)Ph (11)). The molecular structure of 11 was determined by an X-ray investigation. Compound 11 crystallizes in the orthorhombic system, space group P212121, with cell dimensions a = 14.082(1) A?, b = 23.169(2) A?, and c = 25.291(3) A?, and Z = 4. The structure was refined to the following R and Rw values: 0.0414 and 0.0389 for 8343 observed reflections. The cation of 11 can be described as a dinuclear species of 32 valence electrons. Electron counting, to satisfy the 18-electron rule, suggests the presence of an iridium-iridium double bond which is consistent with the observed iridium-iridium distance (2.6592(6) A?). EHT-MO calculations on the model [Ir2H2(PH3)4(μ-H) 2(μ-η2-O2CH)]+ suggests the existence of a partial double bond between the metal atoms. However, the interaction between metals is not based on the direct overlap of the iridium orbitals, but on the three center bonds formed by the bridging system.
Ring slip in associative reactions of some indenyl and phenylcyclopentadienyl iridium complexes
Habib, Afroze,Tanke, Robin S.,Holt, Elizabeth M.,Crabtree, Robert H.
, p. 1225 - 1231 (2008/10/08)
The complex ion [(η5-Ind)IrHL2]+ (Ind = indenyl, L = PPh3) undergoes substitution with t-BuNC, CO, and PMe3, while the Cp analogue (Cp = cyclopentadienyl) is inert. The phenylcyclopentadienyl complex [(η5-PhC5H4)IrHL2]+ undergoes rapid substitution with PMe3 but not with t-BuNC or CO. Slipped η3 and η1 intermediates are proposed in these reactions, and several examples of such complexes are detected by NMR at low temperatures. Deprotonation with n-BuLi takes place only for [(η5-Ind)IrHL2]+ and [(η5-PhC5H4)IrHL2]+, but not the Cp analogue. The reactions of the deprotonated complex [(η5-Ind)IrL2] with a number of electrophiles are also investigated and the resulting cations [(η5-Ind)IrXL2]+ (X = Me, Et, CH2Ph, Cl, I) characterized. The ethyl complex loses ethylene at 60°C by β-elimination, but only in donor solvents, which may attack associatively in the first step of the reaction. In nondonor solvents, the β-elimination is induced by UV photolysis, which may induce ring slip. Allyl bromide reacts with [(η5-Ind)IrL2] to give [(η5-Ind)Ir(η3-allyl)L]+, via [(η5-InD)Ir(η1-allyl)L2]+ as an observed but unisolated intermediate. The structure of the chloro complex [(η5-Ind)IrClL2] was determined by X-ray methods (space group P1; a = 11.314 (4) A?, b = 14.469 (5) A?, c = 13.021 (2) A?, a = 87.05 (2)°, β = 100.25 (2)°, γ = 68.43 (2)°; V = 1934.8 (10) A?3; mol wt = 954.2, Z = 2; F(000) = 944; ρcalcd = 1.638 g cm-3; R = 0.04 for 6379 reflections). Hydrogenation of [(η5-Ind)IrHL2]+ with Rh/C gives the tetrahydroindenyl complex.
