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Biomedical subjects

Luis A Oro

Publications and source records attributed to Luis A Oro.

9 recordsLinked to original sources
PubMed2003

Protonation reactions of dinuclear pyrazolato iridium(I) complexes.

The complex [[Ir(mu-Pz)(CNBu(t))(2)](2)] (1) undergoes double protonation reactions with HCl and with HO(2)CCF(3) to give the neutral dihydride complexes [[Ir(mu-Pz)(H)(X)(CNBu(t))(2)](2)] (X = Cl, eta(1)-O(2)CCF(3)), in which the hydride ligands were located trans to the X groups and in the boat of the complexes, both in the solid state and in solution. The complex [[Ir(mu-Pz)(H)(Cl)(CNBu(t))(2)](2)] evolves in solution to the cationic complex [[Ir(mu-Pz)(H)(CNBu(t))(2)](2)(mu-Cl)]Cl. Removal of the anionic chloride by reaction with methyltriflate allows the isolation of the triflate salt [[Ir(mu-Pz)(H)(CNBu(t))(2)](2)(mu-Cl)]OTf. This complex undergoes a metathesis reaction of hydride by chloride in CDCl(3) under exposure to the direct sunlight to give the complex [[Ir(mu-Pz)(Cl)(CNBu(t))(2)](2)(mu-Cl)]OTf. Protonation of both metal centers in [[Ir(mu-Pz)(CO)(2)](2)] with HCl occurs at low temperature, but eventually the mononuclear compound [IrCl(HPz)(CO)(2)] is isolated. The related complex [[Ir(mu-Pz)(CO)(P[OPh](3))](2)] reacts with HCl and with HO(2)CCF(3) to give the neutral Ir(III)/Ir(III) complexes [[Ir(mu-Pz)(H)(X)(CO)(P[OPh](3))](2)], respectively. Both reactions were found to take place stepwise, allowing the isolation of the intermediate monohydrides. They are of different natures, i.e., the metal-metal-bonded Ir(II)/Ir(II) compound [(P[OPh](3))(CO)(Cl)Ir(mu-Pz)(2)Ir(H)(CO)(P[OPh](3))] and the mixed-valence Ir(I)/Ir(III) complex [(P[OPh](3))(CO)Ir(mu-Pz)(2)Ir(H)(eta(1)-O(2)CCF(3))(CO)(P[OPh](3))].

Journal Article↗
PubMed2003

Stereoselective oxidative additions of iodoalkanes and activated alkynes to a sulfido-bridged heterotrinuclear early-late (TiIr2) complex.

The reactions of the early-late trinuclear complex [Cp(acac)Ti(mu(3)-S)(2)Ir(2)(CO)(4)] (1) with electrophiles have been found to occur on the iridium atoms with no other involvement of the early metal than in electronic effects. The reaction with iodine gave two isomers of the diiridium(II) complex [Cp(acac)Ti(mu(3)-S)(2)Ir(2)I(2)(CO)(4)] differentiated by the relative positions of the iodo ligands on the iridium atoms. The reactions with iodoalkanes are highly stereoselective to give one sole isomer of formula [Cp(acac)Ti(mu(3)-S)(2)Ir(2)(R)(I)(CO)(4)] (R = CH(3), CH(2)I, CHI(2)) with a carbonyl and the iodo ligand trans to the metal-metal bond. The structures of the symmetrical isomer with the iodo ligands trans to the metal-metal bond and that of the compound with R = CHI(2) have been solved by X-ray diffraction methods. The stereoselectivity of the oxidative-addition reactions can be rationalized assuming the influence of steric effects of the groups on the titanium center and a radical-like mechanism. Reactions of 1 with the activated acetylenes, dimethylacetylenedicarboxylate and methylacetylenecarboxylate, gave the complexes [Cp(acac)Ti(mu(3)-S)(2)Ir(2)(mu-eta(1)-RC=CCO(2)Me)(CO)(4)] (R = CO(2)Me, H), with the alkyne bridging the two iridium centers as a cis-dimetalated olefin and the C=C bond parallel to the Ir-Ir axis. Two isomers resulting from the disposition of the alkyne along the Ir-Ir vector were observed in solution for the compound with the nonsymmetrical alkyne (R = H), while only one was observed for the compound with R = CO(2)Me. An exchange, fast in the NMR time scale, of the apical with the equatorial carbonyls occured in the complexes [Cp(acac)Ti(mu(3)-S)(2)Ir(2)(mu-eta(1)-RC=CCO(2)Me)(CO)(4)], producing their equivalence in the (13)C((1)H) NMR spectra.

Journal Article↗
PubMed2002

Structural and dynamic studies on amido-bridged rhodium and iridium complexes.

Treatment of [[M(mu-Cl)(diolefin)](2)] with the lithium salts of primary and secondary amines (LiNRR') in diethyl ether affords the complexes [[M(mu-NRR')(diolefin)](2)] (M=Rh, Ir; diolefin=1,5-cyclooctadiene (cod), tetrafluorobenzobarrelene (tfb); R'=H, R=tBu, Ph, 4-MeC(6)H(4); R=R'=Ph, 4-MeC(6)H(4)). Mixed-bridged chloro/amido complexes are intermediates in these syntheses, two of which, [[Rh(cod)](2)(mu-NHR)(mu-Cl)] (R=tBu, 4-MeC(6)H(4)), have been isolated. Replacement of the diolefin ligands by carbon monoxide or tert-butyl isocyanide in selected compounds takes place with retention of the binuclear structure to give the corresponding complexes [[M(mu-4-HNC(6)H(4)Me)(CO)(2)](2)], [[Rh(mu-4-HNC(6)H(4)Me)(CNtBu)(2)](2)] (12), and [[Rh(mu-NPh(2))(CNtBu)(2)](2)] (13). Single-crystal X-ray diffraction analyses of the complexes [[Rh(mu-NRR')(cod)](2)] (R'=H, R=4-MeC(6)H(4) (3); R=R'=4-MeC(6)H(4) (5)), 12, and 13 have shown that the conformation of the "RhN(2)Rh" four-membered metallacycle is planar in 5 and folded in 3, 12, and 13. The complexes with primary amides, 3 and 12, were found to exist as the syn,endo stereoisomers. The fluxionality of the complexes with secondary amides is due to rotation of the aromatic substituents about the N-C(ipso) bond and, in the case of 13, to the inversion of the "RhN(2)Rh" metallacycle as well. The complexes [[M(mu-NHR)(cod)](2)] (R=Ph, 4-MeC(6)H(4)) were found to exist as isomeric mixtures in solution, the syn/anti ratio being 2:3 for the rhodium derivatives and 1:1 for their iridium counterparts. Again, the motion detected was due to rotation of the aromatic substituents, and could be frozen only in the case of the syn isomers. The complex [[Rh(mu-NHtBu)(cod)](2)] with aliphatic amido ligands was found to be the anti folded isomer and proved to be nonfluxional. The most common conformation of the "RhN(2)Rh" metallacycle in these compounds is folded, and the preferred configuration varies from syn for the less encumbered compounds to anti on increasing the bulkiness of the bridging and ancillary ligands.

Journal Article↗
PubMed2002

Dinuclear rhodium and iridium complexes with mixed amido/methoxo and amido/hydroxo bridges.

The reactions of [[M(mu-OMe)(cod)](2)] (M = Rh, Ir; cod = 1,5- cyclooctadiene) with p-tolylamine, alpha-naphthylamine, and p-nitroaniline gave complexes with mixed-bridging ligands, [[M(cod)](2)(mu-NHAr)(mu-OMe)]. Similarly, the related complexes [[Rh(cod)](2)(mu-NHAr)(mu-OH)] were prepared from the reactions of [[Rh(mu-OH)(cod)](2)] with p-tolylamine, alpha-naphthylamine, and p-nitroaniline. The reactions of [[Rh(mu-OR)(cod)](2)] (R = H, Me) with o-nitroaniline gave the mononuclear complex [Rh(o-NO(2)C(6)H(4)NH)(cod)]. The syntheses of the amido complexes involve a proton exchange reaction from the amines to the methoxo or hydroxo ligands and the coordination of the amide ligand. These reactions were found to be reversible for the dinuclear complexes. The structure of [[Rh(cod)](2)(mu-NH[p-NO(2)C(6)H(4)])(mu-OMe)] shows two edge-shared square-planar rhodium centers folded at the edge with an anti configuration of the bridging ligands. The complex [[Rh(cod)](2)(mu-NH[alpha-naphthyl])(mu-OH)] cocrystallizes with [[Rh(mu-OH)(cod)](2)] and THF, forming a supramolecular aggregate supported by five hydrogen bridges in the solid state. In the mononuclear [Rh(o-NO(2)C(6)H(4)NH)(cod)] complex the o-nitroamido ligand chelates the rhodium center through the amido nitrogen and an oxygen of the nitro group.

Journal Article↗
PubMed2002

Synthesis and molecular structure of [[(HBpz(3))Rh(PPh(3))(mu-Cl)(2)](2)Ag]BF(4) (Hpz = pyrazole), a heterotrinuclear Rh(2)Ag compound with square-planar silver(I).

Reaction of [(HBpz(3))RhCl(2)(PPh(3))] (Hpz = pyrazole) with silver salts AgA (A = BF(4), NO(3), SbF(6)) affords the unexpected heterotrinuclear compounds [[(HBpz(3))Rh(PPh(3))(mu-Cl)(2)](2)Ag]A (A = BF(4) (1), NO(3) (2), SbF(6) (3)). The compounds have been fully characterized by IR, (1)H, (31)P[(1)H], and (13)C[(1)H] NMR spectroscopy and FAB(+) mass spectrometry. The solid structure of compound 1 was determined by single-crystal X-ray diffraction. The cation consists of two (HBpz(3))RhCl(2)(PPh(3)) units bonded to a silver atom through two double mu-Cl bridges in an unusual distorted square-planar arrangement.

Journal Article↗
PubMed2002

Diastereoselective formation of chiral iridium hydrides containing the chiral P,N-chelate ligand (4S)-2-(2-(diphenylphosphino)phenyl)-4-isopropyl-1,3-oxazoline.

The iridium complex [Ir(mu-Cl)(PN)(PPh3)]2 (1) reacts with H2 affording only the kinetic isomer OC-6-55-C of the dihydride [IrClH2(PN)(PPh3)] (2) and with methanol yielding, also exclusively, the thermodynamic isomer OC-6-53-C (2b) of the same dihydride; complex 2b has been characterised by X-ray diffractometric methods.

Chelating Agents↗
PubMed2002

Sequential C-H activation and dinuclear insertion of ethylene promoted by a diiridium complex.

Two ethylene molecules, bonded to different metal atoms of a diiridium(I) complex, can be converted into a bridging 3-butenyl-1-yl ligand and a terminal hydride. Such transformation is initiated by an ethylene C-H activation step and followed by an insertion of the second ethylene into a bridging vinyl ligand. This result illustrates the potentiality of diiridium(I) complexes to promote and support reaction sequences of alkene functionalization through C-H activation.

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