Fernando Viguri

Trimerisation of the Cationic Fragments [(η‐ring)M(Aa)]+ ((η‐ring) M=(η5‐C5Me5)Rh, (η5‐C5Me5)Ir, (η6‐p‐MeC6H4iPr)Ru; Aa=α‐amino acidate) with Chiral Self‐Recognition: Synthesis, Characterisation, Solution Studies and Catalytic Reactions of the Trimers [{(η‐ring)M(Aa)}3](BF4)3

The formation of [{(η-ring)M(Aa)}3](BF4)3trimers [(η-ring)M=(η5-C5Me5)Rh, (η5-C5Me5)Ir, (η6-p-MeC6H4iPr)Ru; Aa = α-amino acidate, one cation shown schematically] takes place by chiral self-recognition, the RMRMRM or SMSMSM trimers are equally configurated at the metal centres and are the only diastereomers detected. The equilibrium constant for the diastereomerisation process between both isomers depends on the solvent, amino acidate, and metal. The trimers catalyse the reduction of unsaturated aldehydes to unsaturated alcohols and the reduction of acetophenone to 2-phenylethanol with up to 75 % ee.

Enantioselective hydride transfer hydrogenation of ketones catalyzed by [(η6-p-cymene)Ru(amino acidato)Cl] and [(η6-p-cymene)Ru(amino acidato)]3(BF4)3 complexes

The new complexes (RRuSC, SRuSC)-[(η6-pCym)Ru(l-Aze)Cl] (6a, b), (RRuSC, SRuSC)-[(η6-pCym)Ru(l-Pip)Cl] (7a, b), (RRuRRuRRuSCSCSCSNSNSN, SRuSRuSRuSCSCSCSNSNSN)-[{(η6-pCym)Ru(l-Aze)}3](BF4)3 (8a, b) and (RRuRRuRRuSCSCSCSNSNSN, SRuSRuSRuSCSCSCSNSNSN)-[{(η6-pCym)Ru(l-Pip)}3](BF4)3 (9a, b) (l-Aze=l-2-azetidinecarboxylate, l-Pip=l-2-piperidinecarboxylate) were prepared, characterized and used, together with the known [{(η6-pCym)Ru(l-Pro)}3](BF4)3, 5 and [{(η6-pCym)Ru(l-Ala)}3](BF4)3, 10 (l-Pro=l-prolinate, l-Ala=l-alaninate), in hydride transfer reduction of acetophenone, a series of substituted acetophenones and several other ketones with moderate to high conversions and enantioselectivities up to 86% e.e.

Chiral rhodium complexes as catalysts in Diels–Alder reactions

The first rhodium enantioselective catalysts for the Diels–Alder reaction between methacrolein and cyclopentadiene are described; the molecular structure of the catalyst precursor [(η5-C5Me5)Rh(R-Prophos)(H2O)][SbF6]2 is also presented.

Bis(diphenylphosphino)amine and their dichalcogenide derivatives as ligands in rhodium(III), iridium(III), and ruthenium(II) complexes. Crystal structures of [(η5-C5Me5)MCl{η2-(SePPh2)2N}] (M=Rh, Ir)

Abstract Reaction of the dimers [{(η 5 -C 5 Me 5 )MCl} 2 (μ-Cl) 2 ] (M=Rh, Ir) or [{(η 6 -arene)RuCl} 2 (μ-Cl) 2 ] (arene= p -MeC 6 H 4 i Pr, C 6 Me 6 ) with NH(PPh 2 ) 2 in the presence of AgA (A=BF 4 , PF 6 ) leads to the mononuclear cationic complexes [(η 5 -C 5 Me 5 )MCl{η 2 -(PPh 2 ) 2 NH}]A (M=Rh ( 1 ), Ir ( 2 )) or [(η 6 -arene)RuCl{η 2 -(PPh 2 ) 2 NH}]A (arene= p -MeC 6 H 4 i Pr ( 3 ), C 6 Me 6 ( 4 )). Similar reactions using the chalcogenide derivatives NH(EPPh 2 ) 2 (E=S, Se) yield the neutral complexes [(η 5 -C 5 Me 5 )RhCl{η 2 -(EPPh 2 ) 2 N}] (E=S ( 5 ), Se ( 6 )), [(η 5 -C 5 Me 5 )IrCl{η 2 -(EPPh 2 ) 2 N}] (E=S ( 7 ), Se ( 8 )), [(η 6 -arene)RuCl{η 2 -(SPPh 2 ) 2 N}] (arene=C 6 H 6 ( 9 ), p -MeC 6 H 4 i Pr ( 10 )) and [(η 6 -arene)RuCl{η 2 -(SePPh 2 ) 2 N}] (arene=C 6 Me 6 ( 11 ), p -MeC 6 H 4 i Pr ( 12 )). Chloride abstraction from complexes 5 – 8 with AgPF 6 in the presence of PPh 3 gives the cationic complexes [(η 5 -C 5 Me 5 )Rh{η 2 -(EPPh 2 ) 2 N}(PPh 3 )]PF 6 (E=S ( 13 ), Se ( 14 )) and [(η 5 -C 5 Me 5 )Ir{η 2 -(EPPh 2 ) 2 N}(PPh 3 )]PF 6 (E=S ( 15 ), Se ( 16 )). Complexes 13 – 16 can also be synthesised from the starting dinuclear complexes, AgPF 6 , NH(EPPh 2 ) 2 and PPh 3 . Using this alternative synthetic route the related ruthenium complexes [(η 6 -C 6 Me 6 )Ru{η 2 -(EPPh 2 ) 2 N}(C 5 H 5 N)] BF 4 (E=S ( 17 ), Se ( 18 )) can be prepared. All described compounds have been characterised by microanalysis and NMR ( 1 H, 31 P) and IR spectroscopy. The crystal structures of the neutral complexes [(η 5 -C 5 Me 5 )MCl{η 2 -(SePPh 2 ) 2 N}] (M=Rh ( 6 ), Ir ( 8 )) have been determined by X-ray diffraction methods. Both complexes exhibit analogous pseudo-octahedral molecular structures with a C 5 Me 5 group occupying three coordination positions and a bidentate chelate Se,Se′-bonded ligand and a chloride atom completing the coordination sphere.

Chiral pyridylamino-ruthenium(II) complexes: synthesis, structure and catalytic properties in Diels–Alder reactions

Half-sandwich complexes [(eta(6)-arene)RuCl(pyam)][SbF(6)] (pyam = L(n) = N-(2-pyridylmethyl)-(R)-1-phenylethylamine (L(1)), N-(2-pyridylmethyl)-(R)-1-naphthylethylamine (L(2)), N-(2-quinolylmethyl)-(R)-1-naphthylethylamine (L(3)), N-(2-pyridylmethyl)-(R)-1-cyclohexylethylamine (L(4)), N-(2-pyridylmethyl)-(1R,2S,4R)-1-bornylamine (L(5))) have been synthetised and characterised. Treatment of these compounds with AgSbF(6) generates dicationic complexes [(eta(6)-arene)Ru(pyam)(H(2)O)](2+) which act as enantioselective catalysts for the Diels-Alder reactions of methacrolein and cyclopentadiene. The catalytic reactions occur quickly at room temperature with good exo : endo selectivity (from 84 : 16 to 98 : 2) and moderate enantioselectivity (up to 74% ee). The molecular structures of the chloride complexes (R(Ru),S(N),R(C))-[(eta(6)-p-MeC(6)H(4)iPr)RuClL(1)][SbF(6)], (R(Ru),S(N),S(C2))-[(eta(6)-p-MeC(6)H(4)iPr)RuClL(5)][SbF(6)], and that of the aqua complex (R(Ru),S(N),S(C2))-[(eta(6)-p-MeC(6)H(4)iPr)RuL(5)(H(2)O)][SbF(6)](2), were determined by X-ray diffractometric methods. The distinctive variations observed in the molecular structures of these complexes only concern the puckering parameters of the metallacycle and the relative disposition of substituents within this ring. A clear trend to localise the most steric demanding substituents at equatorial positions is evident from the structural study.

Binuclear dirhodium(I) complexes with phenyl(2-pyridyl)amido ligands. Crystal and molecular structure of [{Rh(μ-N,N′-PhNPy)(nbd)}2]·H2O (nbd = 2,5-norbomadiene)

The binuclear amidorhodium(I) complexes [{Rh(μ-N,N′-PhNPyR)(diolefin)}2] and [{Rh(μ-N,N′-PhNPyR)(CO)2}2] [PhNPyR = phenyl(2-pyridyl)- amido, phenyl(4-tertbutyl-2-pyridyl)amido; diolefin = 2,5-norbornadiene, tetrafluorobenzobarrelene] are obtained by reaction of the lithium derivatives LiPhNPyR with the appropriate compound [{RhCl(L2)}2] [L2 = diolefin, (CO)2] and characterized by analytical and spectroscopic methods. The crystal structure of [{Rh(μ-N,N′-PhNPy)(nbd)}2]·H2O has been solved by X-ray diffraction methods. The P21/n monoclinic unit cell has dimensions a = 20.7787(12), b = 15.4540(7), c = 10.0162(3) A with β = 92.205(4)°. The final R factor is 0.06 for the 3346 observed reflections. The binuclear unit presents a distorted square-planar coordination around each metal centre with a RhRh separation of 2.959(1) A. The phenyl(2-pyridyl)- amido ligands are bridging the two metallic centres and two 2,5-norbornadiene groups complete the rhodium coordination.

Rhodium(I) and iridium(I) complexes of 2,2′-dipyridylamine and its deprotonated form

Abstract The syntheses and properties of cationic and neutral rhodium(I) and iridium(I) complexes with the 2,2′-dipyridylamine ligand (Hdipy) and its deprotonated form (dipy) are reported. Representative general formulae are: [M(L 2 )(Hdipy)]ClO 4 (M Rh, Ir; L 2 = diolefin, L  CO), [M(CO) 2 (Hdipy)]- [MCl 2 (CO) 2 ], [MCl(diolefin)(Hdipy)] and [M(dipy)- (diolefin)]. The latter complex still has an amide nitrogen available for coordination and is used for the syntheses of the binuclear complexes [(diolefin)- Rh(μ-dipy)Rh(CO)(PPh 3 ) 2 ]ClO 4 and [Rh 2 (μ-dipy)- Cl(diolefin) 2 ]. The crystal and molecular structure of the complex [Rh(dipy)(nbd)] (nbd = 2,5-norbornadiene) has been determined by single-crystal X-ray methods. Crystals are triclinic, space group P 1 with cell constants a = 12.3651(4), b = 12.4386(3), c = 10.0809(3) A, α = 103.209(2), β = 110.278(2), and γ = 88.125(2)°, and Z = 4. The final R and R w values were 0.033 and 0.039 for 4180 observations. The Rh atoms in the two independent molecules in the unit cell present similarly distorted square-planar geometries with both chelate ligands coordinated to each metal atom.

Tris(diphenylthiophosphinoyl)methanide as tripod ligand in rhodium(III), iridium(III) and ruthenium(II) complexes. Crystal structures of [(η5-C5Me5)Ir{η3-(SPPh2)3C-S,S′,S″}]BF4 and [(η6-MeC6H4Pri)Ru{η3-(SPPh2)3C-S,S′,S″}]BPh4

Abstract Reaction of the complex [{(η 5 -C 5 Me 5 )RhCl 2 } 2 ], in CH 2 Cl 2 solution, with AgBF 4 (1:2 molar ratio) and (SPPh 2 ) 3 CH leads to the cationic compound [(η 5 -C 5 Me 5 )RhCl{η 2 -(SPPh 2 ) 2 CH(SPPh 2 )-S,S′}]BF 4 ( 1 ) which is deprotonated by thallium(I) pyrazolate affording [(η 5 -C 5 Me 5 )Rh{η 3 -(SPPh 2 ) 3 C−S,S′,S″}]BF 4 ( 2a ). The iridium dimer [(η 5 -C 5 Me 5 )IrCl 2 } 2 ] reacts with silver salts and (SPPh 2 ) 3 CH, in CH 2 Cl 2 or Me 2 CO, under analogous conditions, affording mixtures of [(η 5 -C 5 Me 5 )IrCl{η 2 -(SPPh 2 ) 2 )-S,S′}] + and [(η 5 -C 5 Me 5 )Ir{η 3 -(SPPh 2 ) 3 C-S,S′,S″}]A [A=BF 4 − ( 3a ), PF 6 − ( 3b ). Addition of Et 3 N to the mixture gives pure complexes 3 . The ruthenium complexes [{η 6 j6-arene)RuCl 2 } 2 ] (arene = C 6 Me 6 , p -MeC 6 H 4 Pr i ) react with (SPPh 2 ) 3 CH, in the presence of AgA (A = PF 6 − or BF 4 − ) or Na BPh 4 , in CH 2 Cl 2 or Me 2 CO, yielding only the deprotonated complexes [(η 6 -arene)Ru{η 3 -(SPPH 2 ) 3 C−S,S′,S″}]A [arene = C 6 Me 6 , A = BF 4 ; arene = p -MeC 6 H 4 Pr i , A - BPh 4 ( 4a ), PF 6 ( 4b )]. The crystal structures of 3a and 4a were established by X-ray crystallography. Compound 3a crystallizes in the orthorhombic space group Pna 2 1 , with lattice parameters a -41.477(6), b = 10.6778(11), c = 20.162(3) A and Z=8. Complex 4a crystallizes in a monoclinic lattice, space group P 2 1 / n , with a = 20.810(4), b = 12.555(3), c = 23.008(4) A, β = 95.82(2)° and Z = 4. Both cationic complexes exhibit analogous pseudo -octahedml molecular structures with the anionic (SPPh 2 ) 3 C − ligand bonded via the three sulphur atoms in a tripodal, tridentate fashion. Each metal centre completes its coordination environment with a η 5 -C 5 Me 5 ( 3a ) or a η 6 -MeC 6 H 4 Pr i group ( 4a ). A quite interesting result concerns the non-planarity of the methanide carbon which display P−C−P angles in the range 112.6–114.4(5)° in 3a and 111.9–113.6(4)° in 4a . The redox chemistry of the complexes was investigated by cyclic voltammetry. The Rh(III) complexes are quasi-reversibly reduced to Rh(I) and the Ir(III) complex is irreversibly reduced to IKD in acetonitrile solutions. The Ru(II) complex undergoes a quasi-reversible reduction to Ru(I) and a reversible oxidation to Ru(III).