Miguel A. Esteruelas

Transition metal liquid crystals: Advanced materials within the reach of the coordination chemist

This review serve to open the field to many coordination chemistry who can use specific expertise of new transition metal liquid crystals. Bibliography

Five- and six-coordinate hydrido(carbonyl)-ruthenium(II) and osmium(II) complexes containing triisopropylphosphine as ligand

Abstract The five-coordinate hydrido(carbonyl) complexes MHCl(CO)(PPri3)2 (I, M = Ru; II, M = Os) have been prepared in excellent yields from MCl3 · aq and PPri3 in methanol. They react with ligands L such as P(OMe)3, PMe3, CO, and olefins CH2CHR (R = H, CO2Me, CN, COMe) to produce the six-coordinate compounds MHCl(CO)(PPri3)2L (III–VI, VIII–XIII). Displacement of the chloride ligand in I,II by acetate or acetylacetonate also leads to the six-coordinate complexes MH(η2-O2CMe)(CO)(PPri3)2 (XVI, XVII) and MH(η2-acac)(CO)(PPri3)2 (XVIII, XIX), respectively. The synthesis of the dichloro complexes trans-OsCl2[P(OPH)3]4 (XXI) and trans-mer-RuCl2(PMe3)3P(OPh)3 (XXII) is also described.

Ruthenium-Catalyzed (2 + 2) Intramolecular Cycloaddition of Allenenes

We report a ruthenium-catalyzed (2 + 2) intramolecular cycloaddition of allenes and alkenes. We have found that the use of the ruthenium complex RuH(2)Cl(2)(P(i)Pr(3))(2), which has previously gone unnoticed in catalytic applications, is crucial for the observed reactivity. The reaction proceeds under mild conditions and is fully diastereoselective, providing a practical entry to a variety of bicyclo[3.2.0]heptane skeletons featuring cyclobutane rings.

Aromatic diosmatricyclic nitrogen-containing compounds.

Aromatic diosmatricyclic nitrogen-containing compounds are prepared from Os(VI) complex OsH6(PiPr3) by double 1,3-C-H bond activation of aromatic six-membered cycles with imino substituents meta disposed.

Osmium-Catalyzed 7-endo Heterocyclization of Aromatic Alkynols into Benzoxepines†

We thank the MICINN (Spain) (CTQ2008-06557, CTQ2008-00810, Consolider Ingenio 2010 (CSD2007-00006)), Xunta de Galicia (2007/XA084 and INCITE08PXIB209024PR) and Diputacion General de Aragon (E35). A.V-F. thanks USC and XUGA for a predoctoral grant. C.G-Y. thanks MICINN for a Ramon y Cajal research contract.

Tris(pyrazol-1-yl)methane-rhodium(I) and -iridium(I) complexes; cyrstal structure of [Rh(COD)(tpzm)][RhCl2(COD)]·3CHCl3

Abstract Fourteen new rhodium and iridium complexes of the tris(pyrazol-1-yl)methane (tpzm) ligand have been prepared. They are of the three types [MCl(diolefin)(tpzm)], [M(diolefin)(tpzm)]Clo 4 , and [M(diolefin)(tpzm)] [MCl 2 (diolefin)], where M is Rh I of Ir I and (diolefin) is a cyclic diolefin (1,5-cyclooctadiene, bicyclo-2,2,1-heptadiene, 5,6,7,8-tetrafluoro-1,4-dihydro-1,4-ethenoaphtalene, or 1,3-dimethyl-5,6,7-,8-tetrafluoro-1,4-dihydro-1,4-ethenonapthalene, or 1,3-dimethyl-5,6,7,8-tetrafluoro-1,4-dihydro-1,4-[9-methyletheno]-napthalene). Addition of [IrCl(COD)] 2 to [RhCl(COD)(tpzm)] gives the complex [Ir(COD)(tpzm)] [RhCl 2 (COD)] owing to the greater tendency of iridium to form five-coordinated species. The crystal structure of [Rh(COD)(tpzm)] [RhCl 2 (COD)] has been determined by X-ray diffraction. The space group is P 1 with a 12.4256(21), b 15.4113(25), c 12.0152(16) A, α 101.48(1), β 105.03(1) and λ 67.21(1)°. The complex exhibits an ionic dinuclear structure and crystallizes with six CHCl 3 molecules per unit cell. In the anion, the Rh(2) atom is in a square-planar arrangement and in the cation the coordination around Rh(1) is that of a distorted trigonal bipyramid. A careful 13 C and 1 H NMR spectra study has been carried out, with particular emphasis on the assignment of the pyrazole signals. The shifts induced by complexation (larger in the 1 H NMR spectra for iridium than for rhodium), the dynamics aspects, and the COD signals are discussed.

Homogeneous catalysis by osmium complexes. A review

Abstract Homogeneous catalysis by osmium complexes is more promising than hitherto realized. Most of the reactions studied have concentrated on simple model substrates, and therefore a demonstration of the utility of these catalysts for reactions of more sophisticated organic molecules is needed; highly selective reduction of terminal and internal carbon-carbon triple bonds in presence of other unsaturations within the same molecule should become an immediate goal. In view of the excellent results obtained in the asymmetric dihydroxylation of alkenes, other highly enantioselective processes, such as hydrogenation, oligomerization, hydrosilylation and hydroformylations may be envisaged with osmium complexes; catalytic activation of CH, CS, CN, NH, and OH bonds also seem reasonable and important targets. As a consequence of the high thermal and oxidative stability observed for osmium complexes, their syntheses, manipulation, and recycling may prove much simpler than for analogous, less robust catalysts derived from other metals, and these advantages may counter the higher cost involved in the case of osmium. Furthermore, this enhanced stability will certainly be convenient for kinetic and mechanistic studies which could lead to a deep understanding of the catalytic chemistry.

Catalytic transfer hydrogenation by cationic rhodium(I) complexes

Summary Complexes formed by adding Group Vb ligands to [Rh(NBD) 2 ]ClO 4 in the presence of potassium hydroxide catalyze hydrogen transfer from isopropanol to acetophenone, cyclohexene and other unsaturated substrates. The catalytic activity depends upon the nature of the mono- or bidentate nitrogen-or phosphorus-donor ligands. [Rh(NBD) {P( p -MeOC 6 H 4 ) 3 }ClO 4 catalyses the selective reduction of hexyne or diolefins.

POP-Pincer Silyl Complexes of Group 9: Rhodium versus Iridium

9,9-Dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(P(i)Pr2)2) derivatives RhCl{xant(P(i)Pr2)2} (1) and I rHCl{xant(P(i)Pr2)[(i)PrPCH(Me) CH2]} (2) react with diphenylsilane and triethylsilane to give the saturated d(6)-compounds RhHCl(SiR3){xant(P(i)Pr2)2} (SiR3 = SiHPh2 (3), SiEt3 (4)) and IrHCl(SiR3){xant(P(i)Pr2)2} (SiR3 = SiHPh2 (5), SiEt3 (6)). Complexes 3 and 5 undergo a Cl/H position exchange process via the MH{xant(P(i)Pr2)2} (M = Rh (8), Ir (E)) intermediates. The rhodium complex 3 affords the square planar d(8)-silyl derivative Rh(SiClPh2){xant(P(i)Pr2)2} (7), whereas the iridium derivative 5 gives IrH2(SiClPh2){xant(P(i)Pr2)2} (9), which is stable. In agreement with the formation of 7, the reactions of 8 with silanes are a general method to prepare square planar d(8)-rhodium-silyl derivatives. Thus, the addition of triethylsilane and triphenylsilane to 8 initially leads to the dihydrides RhH2(SiR3){xant(P(i)Pr2)2} (SiR3 = SiEt3 (10), SiPh3 (11)), which lose molecular hydrogen to afford Rh(SiR3){xant(P(i)Pr2)2} (SiR3 = SiEt3 (12), SiPh3 (13)). Treatment of 7 with NaBAr(F)4·2H2O leads to the cationic five-coordinate d(6)-species [RhH{Si(OH)Ph2}{xant(P(i)Pr2)2}]BAr(F)4 (14) through a silylene intermediate. According to the participation of the latter in the formation of 14, this cation is an efficient catalyst precursor for the monoalcoholysis of diphenylsilane with a wide range of alcohols, reaching turnover frequencies at 50% of conversion between 4000 and 76 500 h(-1). The X-ray structures of 3, 6, 7, 9, 12, and 14 are also reported.

Bis-alkynyl- and hydrido-alkynyl-osmium(II) and ruthenium(II) complexes containing triisopropylphosphine as ligand

Abstract The five-coordinate bis-alkynyl complexes M(CCPh) 2 (CO)(P-i-Pr 3 ) 2 (M = Os, Ru) have been prepared by reaction of HCCPh with OsH 4 (CO)(P-i-Pr 3 ) 2 or MH( h 2 -H 2 BH 2 )(CO)(P-i-Pr 3 ) 2 (M = Os, Ru). They react with ligands L such as P(OMe) 3 , PMe 3 , CO and HCCPh to give the six-coordinate compounds M(CCPh) 2 (CO)(P-i-Pr 3 ) 2 L. Displacement of the chloride ligands in MHCl(CO)(PR 3 ) 2 L by CCPh − leads to the hydrido-alkynyl compounds MH(CCPh)(CO)(PR 3 ) 2 L. The selective reduction of phenylacetylene to styrene catalysed by the complex OsH 4 (CO)(P-i-Pr 3 ) 2 , prepared from OsHCl(CO)(P-i-Pr 3 2 and NaBH 4 in situ, is also described.