M. Pilar Lamata

On the Sense of the Enantioselection in Hydrogen Transfer Reactions from 2-Propanol to Ketones

An explanation for the reversal in the sense of the enantioselectivity observed in hydrogen transfer reactions from 2-propanol to ketones catalyzed by the ruthenium or osmium amino acidates [(η6-p-MeC6H4-i-Pr)M(Aa)Cl] and [(η6-p-MeC6H4-i-Pr)M(Aa)]3[BF4]3 [Aa=piperidine-2-carboxylate (pip), N-methyl-L-phenylalaninate (MePhe)] is given; the molecular structures of [(η6-p-MeC6H4-i-Pr)Os(Pip)Cl] (1), [(η6-p-MeC6H4-i-Pr)Os(Pip)]3[BF4]3 (2), [(η6-p-MeC6H4-i-Pr)M(MePhe)Cl] [M=Ru (3), Os (4)] are also reported.

Synthesis, characterization and molecular structure of the hydroperoxo complex [(η5C5Me5)Ir(µ-pz)3Rh(OOH)(dppe)][BF4]; Hpz = pyrazole, dppe β 1,2-bis(diphenylphosphino)ethane

The synthesis and structural characterization of the title hydroperoxide complex is described.

Di(μ-pyrazolate)bis(pentamethylcyclopentadienyl)rhodium complexes. Molecular structure of [{Rh(C5Me5)(pz)} 2(μ-pz = pyrazolate)

Abstract Neutral and cationic complexes of the general formulae [{Rh(C5Me5)(Pz)}2(μ-Pz)2] and [{Rh(C5Me5)(HPz)}2(μ-Pz)2](ClO4)2 were prepared, starting from the dinuclear tri-μ-hydroxo bridged complex [{Rh(C5Me5)}2(μ-OH)3]ClO4. The interconversion between these two types of structures in acidic or basic media were studied. The structure of the title complex was established by X-ray crystallography. The complex crystallizes in the space group P21/n with cell dimensions of a = 13.4979(4), b = 10.1424(2), c = 11.7565(3) A, β = 103.765(2)°. The compound has an internal crystallographic center of symmetry relating the two halves of the molecule. The two rhodium atoms are separated by 4.103(1) A.

Di- and tetra-nuclear mixed-valence complexes of rhodium(III,I) and rhodium(III)–iridium(I) with the 2,2′-bi-imidazolate(2–) anion (bim) as bridging ligand. Crystal structure of [{(η-C5Me5)[P(OEt)3]Rh(bim)Rh(nbd)}2][ClO4]2

The reaction of the new mononuclear species [RhIII(η-C5Me5)Cl(Hbim)](H2bim = 2,2′-bi-imidazole) and [RhIII(η-C5Me5)(Hbim)L′][ClO4][L′= pyridine (py), NCBut, PPh3, or P(OEt)3] with the corresponding acetylacetonate (acac) complexes of formulae [MI(acac) L2][M = Rh; L = CO, L2= tetrafluorobenzobarrelene (tfb)(5,6,7,8- tetrafluoro-1,4-dihydro-1,4-ethenonaphthalene) or norborna-2,5-diene (nbd). M = Ir, L2= tfb] yields di- and tetra-nuclear mixed-valence compounds of the types [{(η-C5Me5)ClRhIII(bim)RhIL2}2][L = CO or L2= tfb], [{(η-C5Me5) L′RhIII(bim) RhI L2}n][ClO4]n[L′= py; L2= tfb (n= 1). L′= py; L = CO or L2= nbd (n= 2). L′= NCBut, PPh3, or P(OEt)3; L = CO, L2= tfb or nbd (n= 2)] and [{(η-C5Me5)L′RhIII(bim)IrI(tfb)}n][ClO4]n[L′= py (n= 1), L′= PPh3 or P(OEt)3(n= 2)]. The structure of [{(η-C5Me5)[P(OEt)3] RhIII(bim) RhI(nbd)}2][ClO4]2 has been determined by X- ray diffraction methods. Crystals are orthorhombic, space group Fddd with Z= 16 in a unit cell of dimensions a= 21.337(3), b= 41.943(5), and c= 31.815(7)A. The structure was solved by direct and Fourier methods and refined by full- matrix least squares to R= 0.075 for 2 984 observed reflections. The complex cation [{(η-C5Me5)[P(OEt)3] RhIII(bim) RhI(nbd)}2]2+, having imposed C2symmetry, is tetranuclear with two bim2– ligands bridging the metal atoms. Each bim2– anion co- ordinates to the Rh metals in an unsymmetrical tetradentate manner through its four nitrogen atoms of the two imidazolate rings, being chelated to one formally six-co-ordinated Rh atom [Rh(1)] through two N atoms and being bonded in an unidentate manner to two four-co-ordinated Rh atoms [Rh(2)], through the other two N atoms. The co-ordination around Rh(1) is completed by an η-C5Me5 group and by a P(OEt)3ligand, that around Rh(2) by a nbd molecule interacting through the two double bonds. A short non-bonding Rh(2)–Rh(2′) distance [3.250(5)A] is present in the cation.

Chiral transition-metal complexes as Brønsted-acid catalysts for the asymmetric Friedel–Crafts hydroxyalkylation of indoles

The Friedel-Crafts reaction between 3,3,3-trifluoropyruvates and indoles is efficiently catalysed by the iridium complex [(η(5)-C5Me5)Ir{(R)-Prophos}(H2O)][SbF6]2 (1) with up to 84% ee. Experimental data and theoretical calculations support a mechanism involving the Brønsted-acid activation of the pyruvate carbonyl by the protons of the coordinated water molecule in 1. Water is not dissociated during the process and, therefore, the catalytic reaction occurs with no direct interaction between the substrates and the metal.

Chiral ruthenium complexes as catalysts in enantioselective Diels–Alder reactions. Crystal structure of the Lewis acid–dienophile adduct

On the basis of spectroscopic and structural studies a full catalytic cycle is proposed for the Diels–Alder reaction between methacrolein and cyclopentadiene when the new chiral aquo-complexes (RRu, SRu)-[(η6-p-cymene)Ru(PN)(H2O)][SbF6]2 {PN = (3aS, 8aR)-2-(2-diphenylphosphinophenyl)-3a,8a-dihydroindane[1,2-d]oxazole} are used as catalysts.

Homo- and hetero-binuclear complexes containing the anion [Rh(C5Me5){PO(OMe)2}2(pyrazolate)]– as ligand. Crystal structure of [(C5Me5)Rh{µ-PO(OMe)2}2(µ-C3H3N2)-Ru(C6H6)]ClO4·CH2Cl2

The neutral rhodium(III) complex [Rh(C5Me5)I{PO(OMe)2}{P(OH)(OMe)2}] reacts with pyrazole-type ligands [HL = pyrazole (Hpz), 3-methylpyrazole, or 3,5-dimethylpyrazole] in the presence of AgClO4 yielding cationic complexes of the general formula [Rh(C5Me5){PO(OMe)2}{P(OH)(OMe)2}(HL)]ClO4. They react with Na2CO3 in aqueous solutions with formation of the neutral complexes [Rh(C5Me5){PO(OMe)2}2(HL)]. Addition of NaH in tetrahydrofuran to the cationic complexes or thallium acetylacetonate in MeOH to the neutral compounds affords the corresponding bimetallic derivatives [(C5Me5)Rh{PO(OMe)2}2LM](M = Na or Tl). These complexes react with halide compounds such as [{M(ring)Cl2}2][M(ring)= Rh(C5Me5), Ir(C5Me5), Ru(C6H6), Ru(C6H5Me), Ru(MeC6H4Pri-p) or Ru(C6Me6)], [MBr(CO)5], [(PtMe3I)4] or [{Rh(µ–Cl)(cod)}2](cod = cycloocta-1,5-diene) to give cationic or netural complexes of the type [(C5Me5)Rh{µ-PO(OMe)2}2(µ-L)-M(ring)]ClO4 or [(C5Me5)Rh{PO(OMe)2}2(µ-L)MLn][MLn= Re(CO)3, Mn(CO)3, PtMe3 or Rh(cod)]. The crystal structure of [(C5Me5)Rh{µ-PO(OMe)2}2(µ-pz)Ru(C6H6)]ClO4·CH2Cl2 has been determined by X-ray diffraction methods: monoclinic, space group P21/c, a= 11.179(1), b= 17.039(1), c= 18.186(2)A, β= 94.85(1)° and Z= 4. The complex cation consists of one rhodium and one ruthenium atom bridged by two phosphonate and one pyrazolate anion. An η5-C5Me5 and an η6-C6Me6 group complete the co-ordination spheres of the metals, which show no direct intermetallic interaction.

Synthesis and characterization of the alkoxycarbonyl complexes [(C5Me5)M(µ-pz)(µ-I)2Rhl(CO2R)(CO)](M = Rh, R = Me or Et; M = Ir, R = Me; pz = pyrazolate). Molecular structure of [(C5Me5)Ir(µ-pz)(µ-I)2Rhl(CO2Me)(CO)]

The alkoxycarbonyl complexes [(C5Me5)M(µ-pz)(µ-I)2Rhl(CO2R)(CO)][M = Rh, R = Me, (4), or Et, (5); M = Ir, R = Me, (6); pz = pyrazolate] were prepared by treating the corresponding dicarbonyl complex [(C5Me5)ClM(µ-pz)2Rh(CO)2][M = Rh, (1), or Ir, (3)] with molecular iodine in methanol [(4), (6)] or ethanol [(5)] and in the presence of sodium salts (i.e. NaBPh4, NaI·2H2O). The molecular structure of compound (6) was determined by X-ray diffraction: monoclinic space group C2/c with a= 28.574(3), b= 8.688(1), c= 19.321 (2)A, β= 96.44(1)°, and Z= 8. The structure was refined to R= 0.037 for 2 789 observed reflections [F 5.0σ(F)] and 236 parameters. The complex is dinuclear with the two metals, bridged by two iodides and a pyrazolate ligand. The rhodium exhibits distorted-octahedral co-ordination involving three terminal ligands: an iodide, a carbonyl, and a methoxycarbonyl group formed during the preparative reaction.

Asymmetric 1,3-dipolar cycloaddition reactions between enals and nitrones catalysed by half-sandwich rhodium or iridium diphosphane complexes

The aqua complexes [(η5-C5Me5)M(PP*)(H2O)][SbF6]2 (M = Rh, Ir; PP* = chiral diphosphane) have been tested as catalysts for the asymmetric 1,3-dipolar cycloaddition of nitrones to α,β-unsaturated aldehydes. Quantitative conversions with very high regioselectivity, perfect endo selectivity and excellent enantioselectivity (up to 99% ee) were achieved. The stereochemical outcome was analyzed on the basis of the stereoelectronic properties of the intermediate enal complexes of the formula [(η5-C5Me5)M(PP*)(enal)][SbF6]2.

Syntheses and characterization of binuclear Rh2, Ir2 and RhIr complexes containing dimethyl phosphonate and pyrazolate bridging ligands

The reaction of [Ir(η5-C5Me5)I{PO(OMe)2}{P(OH)(OMe)2}] with pyrazole (Hpz) in the presence of AgPF6 gave [Ir(η5-C5Me5){PO(OMe)2}{P(OH)(OMe)2}(Hpz)]PF61. Deprotonation of 1 with sodium carbonate afforded the neutral compound [Ir(η5-C5Me5){PO(OMe)2}2(Hpz)]2 which, in turn, can be deprotonated to [(η5-C5Me5)Ir{PO(OMe)2}2(pz)M′](M′= Tl 3 or Na 4) by Tl(acac)(acac = acetylacetonate) or NaH, respectively. The complex [Ir(η5-C5Me5)I2{P(OH)(OMe)2}]5, prepared by cleaving the iodide bridges in [{Ir(η5-C5Me5)I}2(µ-I)2] with HPO(OMe)2, reacted with Hpz in the presence of AgPF6 to give [Ir(η5-C5Me5){PO(OMe)2}(Hpz)2]PF66. Complexes of formulae [(η5-C5Me5)Ir{PO(OMe)2}2(pz)M″L2][M″L2= Rh(CO)27, Rh(cod)8 or Ir(cod)9] were prepared from 2 and [Rh(acac)(CO)2] or from 3′ and the appropriate [{M″(cod)}2(µ-Cl)2] dimer (cod = cycloocta-1,5-diene). Complex 6 reacted with [{Rh(cod)}2(µ-Cl)2] in basic medium to give [(η5-C5Me5)Ir{PO(OMe)2}(pz)2Rh(cod)]10. The rhodium–thallium compound [(η5-C5Me5)Rh{PO(OMe)2(pz)Tl] or the in situ prepared sodium derivative [(η5-C5Me5)Rh{PO(OMe)2}(pz)2Na] reacted with the dimers [{M″(diolefin)}2(µ-Cl)2] affording [(η5-C5Me5)Rh{PO(OMe)2}2(pz)M″(diolefin)][M″(diolefin)= Ir(cod)11 or Rh(nbd)12] or [(η5-C5Me5){PO(OMe)2}Rh(pz)2M″(diolefin)][M″(diolefin)= Rh(cod)13, Ir(cod)14 or Rh(nbd)15], respectively (nbd = bicyclo[2.2.1]hepta-2,5-diene). Related heterovalent complexes of general formula [I(η5-C5Me5)M{PO(OMe)2}2M″(diolefin)][M = Ir, M′(diolefin)= Rh(cod)16 or Ir(cod)17; M = Rh, M″(diolefin)= Rh(cod)18, Ir(cod)19, or Rh(nbd)20] have been prepared starting from the mononuclear complexes [M(η5-C5Me5I{PO(OMe)2}{P(OH)(OMe)2}](M = Ir or Rh). All the complexes have been characterized by spectroscopic means and the fluxional behaviour of 7–9, 11 and 12, in solution, has been studied. The protonation of 8 by toluene-p-sulfonic acid is reported. The structures of 8 and 16 have been determined by X-ray diffraction methods. Both complexes consist of doubly bridged binuclear (C5Me5)Ir–Rh(cod) species, where the Ir atoms exhibit pseudo-octahedral coordination and the rhodium square planar. The bridging system in 16 is formed by two identical P,O-bonded phosphonate groups, while in 8 a pyrazolate and a phosphonate ligand are bridging the metals. The intermetallic separations are 4.0445(9)(8) and 4.0928(9)A(16).