Six-coordinate Ruthenium Research Articles

Front Cover: Heterobridged Hexa‐ and Octanuclear Ruthenium‐Thiolate/Halide Wheels: Synthesis, X‐ray Crystal Structure, and Spectroscopic Characterization (Eur. J. Inorg. Chem. 33/2022)

The Front Cover shows the structure of an octanuclear heterobridged molecular wheel featuring six-coordinate ruthenium ions, terminal CO ligands, and thiolate/iodide mixed bridging ligands. This wheel represents one of the crystallographically characterized {Run(μ-SR)n(μ-X)n}(CO)2n (X=Cl, Br, n=6; X=I, n=8) wheels composed of edge-shared RuC2S2X2 (X=halide) octahedra. The present work demonstrates the construction of hexa- and octanuclear wheels which feature fused Mn(μ-SR)n/Mn(μ-X)n (n=6, 8) metallamacrocycles as well as six-coordinate metal molecular wheels with their metal ions linked by mixed S/X-donor ligands. More information can be found in the Research Article by J.-S. Huang, C.-M. Che and co-workers.

Six-coordinate ruthenium water oxidation catalysts bearing equatorial polypyridinedicarboxylato and axial phosphine ligands

Ruthenium catalysts for water oxidation combining multidentate ligands [2,2′:6′,2″-terpyridine]-6,6″-dicarboxylato (tda) and 2,2′-bipyridine-6,6′-dicarboxylato (bda) with apical phosphine ligands have been prepared. These new complexes were fully characterized by standard spectroscopic and single-crystal X-ray crystallography analyses, and their redox properties were evaluated by electrochemistry. Specifically, [RuII(tda)(tris(2-furyl)phosphine)2] displayed two reversible redox waves that were assigned to the RuII/III and RuIII/IV transitions, respectively. The number of turnovers in CeIV-driven water oxidation reached 258 for the bda analog, and for the tda analog, early reaction rates were first order in initial catalyst concentration. The effects of adding fractional equivalents of CeIV were studied using UV–vis spectroscopy. Steric and electronic changes in the axial phosphine ligand can exert their effects on the properties and catalytic activity of the resulting complexes, which may be useful when exploring other chemistry of these complexes.

Ruthenium(II) and Ruthenium(III) Complexes of p-Benziporphyrin: Merging Equatorial and Axial Organometallic Coordination.

A diamagnetic ruthenium(II) complex of 5,10,15,20-tetraphenyl-p-benziporphyrin [RuII(p-BzP)(CO)Cl] was obtained via the insertion of ruthenium into p-benziporphyrin using triruthenium(0) dodecacarbonyl [Ru3(CO)12] as the metal source. The procedure applying dichloro(cycloocta-1,5-diene)ruthenium(II) (polymer, [Ru(COD)Cl2]n) afforded the paramagnetic six-coordinate ruthenium(III) p-benziporphyrin [RuIII(p-BzP)Cl2]. As shown by X-ray crystallography, the p-phenylene ring in both complexes is sharply tilted out of the N3 plane, as reflected by the respective N3 (pyrrole)-C6 (p-phenylene) dihedral angle [RuII(p-BzP)(CO)Cl, 52.5°; RuIII(p-BzP)Cl2, 53.7°]. p-Phenylene is bound to the ruthenium cation in an η2 fashion, revealing the shortest ever Ru-C distance in the series of p-benziporphyrin complexes [RuII(p-BzP)(CO)Cl, 2.275(2) Å; RuIII(p-BzP)Cl2, 2.324(5) Å]. The reaction of RuII(p-BzP)(CO)Cl with ArMgCl or AlkMgCl results in the formation of diamagnetic six-coordinate ruthenium(II) p-benziporphyrin complexes containing the apically coordinated σ-alkyl or σ-aryl ligands, where the metal ion simultaneously coordinates to three carbon centers respectively accommodating η2 (phenylene) and σ (aryl and alkyl) modes. Reactions of σ-aryl (alkyl) carbanions with paramagnetic RuIII(p-BzP)Cl2 have been followed by 1H NMR spectroscopy. The procedure afforded the six-coordinate paramagnetic ruthenium(III) p-benziporphyrin [RuIII(p-BzP)(Ph)Cl], which binds one σ-aryl ligand, as reflected by the characteristic 1H NMR spectra spread within the +120 to -120 ppm range. Both paramagnetic complexes RuIII(p-BzP)(Ph)Cl and RuIII(p-BzP)(p-Tol)Cl are formed as a mixture of two stereoisomers differentiated by two nonequivalent locations of σ-aryl with respect to the puckered macrocyclic ring. The paramagnetic shifts of σ-aryls are indicative of π-spin delocalization patterns. Analysis of the contact shifts and parallel density functional theory calculations of the spin density distribution in RuIII(p-BzP)Cl2, RuIII(p-BzP)(Ar)Cl, and RuIII(p-BzP)(Alk)Cl reflect the features of the dxy2(dxzdyz)3 electronic ground state.

A ruthenium(II) complex having a ligand undergoing partial C = N cleavage and unusual double-bond shift and nonchirality

A novel six-coordinate ruthenium(II) complex 1, formulated as [Ru(bpy)2Lb]PF6⋅C2H5OH (bpy=2,2′-bipyridine), has been obtained and characterized. Ligand Lb in 1 comes from a chiral bis-Schiff-base ligand La which is condensed between sodium(I) salt of D- or L-phenylanine and terephthaldicarboxaldehyde. It is noted that ligand La undergoes partial C=N bond cleavage of Schiff-base unit forming a free aldehyde group at one end of phenyl ring, and an unusual proton migration, a C=N double-bond shift and subsequent nonchirality at the other end simultaneously in the presence of a ruthenium(II) ion.

Structural and Mechanistic Basis of the Fast Metathesis Initiation by a Six-Coordinated Ruthenium Catalyst

The N-heterocyclic carbene coordinated ruthenium benzylidene complex [(H2IMes)(PCy3)(Cl)2Ru═CHPh], a highly active olefin metathesis catalyst, is known to convert into a very fast initiator in the presence of pyridine or 3-bromopyridine. Computational studies presented in this work reveal the mechanistic basis of this phenomenon. Depending on the size of the olefin, the reaction follows either a dissociative or associative mechanism.

Synthesis and Crystal Structure of a New Ru(II) Complex With Dicationic 2,2′-Dipyridyl Derivatives as Ligand

A new Ru(II) complex [Ru(bpy)2(5,5′-((n-Bu)3NCH2)2-bpy)](PF6)4·2CH3CN was synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, UV spectra, and emission spectra. The complex crystallizes to triclinic P-1 with dimensions a = 13.0051(5) Å, b = 13.6617(5) Å, and c = 22.6481 (1) Å; angles α = 72.560(3)°, β = 75.354(5)°, and γ = 83.264(3)°; and V = 3710.5(2) Å3, Z = 2, and R1 = 0.0672. The structure of cation [Ru(bpy)2(5,5′-((n-Bu)3NCH2)2-bpy)]4+ consists of a six-coordinated ruthenium atom chelated by two bpy ligands and one dicationic [5,5′-((n-Bu)3NCH2)2-bpy]2+ ligand. Absorption spectra of the Ru(II) complex were characterized by two intense ligand-centered transitions in the UV region and metal-to-ligand-charge transfer in the visible region. Moreover, the complex can display luminescence in water at ambient temperatures with a maximum at 644 nm.

Solvent effect for ruthenium porphyrin

Relaxation of electronic excited-state and vibrational dynamics in the electronic excited state in RuII(TPP)(CO) [TPP=tetraphenylporphyrin] dissolved in N2 bubbled benzene, O2 bubbled benzene, N2 bubbled chloroform and N2 bubbled acetone were clarified using a sub-5fs laser pulse. The result showed that the transition energy from the 1Qx states, consisting of the 1Qx(1,0)(π,π*) state (existing at 18800 cm−1) and 1Qx(0,0)(π,π*) state (existing at 17800 cm−1), to the 1M state of six-coordinated ruthenium complex is lower than that of the five-coordinated ruthenium complex. The intersystem crossing 1Qx(0,0)(π,π*)→3(d,π*) in the five-coordinate RuII(TPP)(CO) in the solution was found to take place in about 1 ps.

Ruthenium(III) tetradentate Schiff-base complexes: spectral, catalytic, and its biocidal efficacy

New six-coordinate ruthenium(III) Schiff-base complexes of general formula [Ru(X)(PPh3)(L)] (where X = Cl/Br and L = mononucleating bibasic tetradentate ligand derived by condensing actetoacetanilide/acetoacetotoludide with o-aminophenol/o-aminothiophenol/o-aminobenzoic acid in 1 : 2 molar ratio in ethanol) have been synthesized and characterized by physico-chemical and spectroscopic methods. The new ruthenium(III) complexes possess 2NO/2NS metal binding sites and are catalysts for the oxidation of alcohols using molecular oxygen as co-oxidant and in C–C coupling reactions. These complexes possess good biocidal (antibacterial and antifungal) activity.

Ruthenium(II) unsymmetrical N2O2 tetradentate Schiff-base complexes: synthesis, characterization, and catalytic studies

A series of six-coordinate ruthenium(II) complexes [Ru(CO)(L x )(B)] (B = PPh3, AsPh3 or Py; L x = unsymmetrical tetradentate Schiff base, x = 5–8; L5= salen-2-hyna, L6= Cl-salen-2-hyna, L7= valen-2-hyna, L8= o-hyac-2-hyna) have been prepared by reacting [RuHCl(CO)(EPh3)2(B)] (E = P or As) with unsymmetrical Schiff bases in benzene under reflux. The new complexes have been characterized by analytical and spectroscopic (infrared, electronic, 1H, 31P, and 13C NMR) data. An octahedral structure has been assigned for all the complexes. The new complexes are efficient catalysts for the transfer hydrogenation of ketones and also exhibit catalytic activity for the carbon–carbon coupling reactions.

Studies on ruthenium(III) chalcone thiosemicarbazone complexes as catalysts for carbon–carbon coupling

New six-coordinate ruthenium(III) complexes [RuX(EPh3)2(L)] (X = Cl or Br; E = P or As; L = chalcone thiosemicarbazone) have been prepared by reacting [RuX3(EPh3)3] (X = Cl or Br; E = P or As) with chalcone thiosemicarbazones in benzene under reflux. The new complexes have been characterized by analytical and spectroscopic (IR, electronic, mass, and EPR) data. The redox behavior of the complexes has also been studied. Based on the above data, an octahedral structure has been assigned for all the complexes. The new complexes exhibit catalytic activity for carbon–carbon coupling reactions.

Redox Gradations in Ruthenium Porphycene Complexes and the Porphyrin Analogs: Axial and Macrocyclic Ligand Effects

Abstract This paper reports synthesis and electrochemistry of six-coordinate ruthenium porphyrin isomers including six novel porphycene complexes with substituted pyridines in the axial positions, in which redox potential control of reversible RuII/RuIII processes is successfully achieved over a 0.7-V potential region by varying the axial ligands and tetrapyrrole ligand structure and substituents.

DFT study of metastable linkage isomers of six-coordinate ruthenium nitrosyl complexes

Abstract The linkage isomers of the [M(NO)(CN)5]2− (M = Fe, Ru, Os), [Ru(NO)Cl5]2−, trans-[Ru(NO)(NH3)4(L)]q+ (L = NH3, H2O, nicotinamide, imidazole, pyridine, pyrazine, NO2 −, OH−, Cl−), and trans-[Ru(NO)L4(OH)]q (L = pyridine, NO2 −) ions are studied by density functional theory. DFT calculations show that the electronic ground-state potential surface of these nitrosyl complexes has the local minima corresponding to η 2-NO and η 1-O linkage isomers, of which the former is characterized by lower energy. The stationary points on the ground state potential energy surface along the GS → MS2 → MS1 path for the [M(NO)(CN)5]2− (M = Fe, Ru, Os) and [Ru(NO)Cl5]2− complexes were found. The calculations of infrared spectra of linkage isomers [Ru(NO)Cl5]2− and [Ru(NO)(CN)5]2− are carried out. The analysis of quantum chemical bond orders indicates a noticeable delocalization of π-electron density along the Ltrans—M—NO axis and a possibility of direct interactions between NO and equatorial ligands in the structures with the bent {MNO} group.

Redetermination ofcis-diacetonitrilebis(2,2′-bipyridine)ruthenium(II) hexafluorophosphate

The title compound, [Ru(C10H8N2)2(CH3CN)2](PF6)2, a six-coordinate ruthenium(II) complex, crystallizes in the monoclinic C2/c space group showing different symmetry from the previously reported P21/n. A crystallographic twofold rotation axis passes through the Ru atom. The two C atoms and H atoms of one acetonitrile ligand are disordered over two positions, with site occupancy factors of ca 0.55 and 0.45. Three F atoms are disordered over two positions, with similar site occupancy factors.

Synthesis, Structure, and Reactivity of Four-, Five-, and Six-Coordinate Ruthenium Carbyne Complexes

Square-planar carbyne complexes of the form Ru(⋮CR)(PCy3)2X (X = F, Cl, Br, I, O3SCF3) are prepared by net dehydrohalogenation of the Grubbs catalysts Ru(CHR)(PCy3)2Cl2 followed by substitution of the chloride ligand (when X ≠ Cl). The dehydrohalogenation can be effected in one step (R = n-Bu, Ph, p-C6H4Me) by Ge(CH[SiMe3]2)2 or in two steps via treatment with excess aryloxide such as NaO-p-C6H4-t-Bu followed by SnCl2. The latter route gives greater yields but is more restricted in scope. Addition of HCl (1 equiv) to Ru(⋮CR)(PCy3)2X (X = Cl, Br, I) affords Ru(CHR)(PCy3)2ClX; those with mixed halide ligand sets undergo rapid halide exchange in solution. Upon treatment with the appropriate oxidant, each Ru(⋮C-p-C6H4Me)(PCy3)2X complex undergoes two-electron oxidation. Oxidation of Ru(⋮C-p-C6H4Me)(PCy3)2X (X = F, Cl, Br, I) by XeF2, C2Cl6, Br2, and I2, respectively, yields either six-coordinate bis-phosphine complexes Ru(⋮C-p-C6H4Me)(PCy3)2X3 (X = F, Cl) or square-pyramidal mono-phosphine complexes Ru(⋮C-p-C...

Synthesis, structure and spectral and redox properties of new mixed ligand monomeric and dimeric Ru(ii) complexes: predominant formation of the “cis-α” diastereoisomer and unusual3MC emission by dimeric complexes

The tetradentate ligands 1,8-bis(pyrid-2-yl)-3,6-dithiaoctane (pdto) and 1,8-bis(benzimidazol-2-yl)-3,6-dithiaoctane (bbdo) form the complexes [Ru(pdto)(mu-Cl)](2)(ClO(4))(2) 1 and [Ru(bbdo)(mu-Cl)](2)(ClO(4))(2) 2 respectively. The new di-mu-chloro dimers 1 and 2 undergo facile symmetrical bridge cleavage reactions with the diimine ligands 2,2'-bipyridine (bpy) and dipyridylamine (dpa) to form the six-coordinate complexes [Ru(pdto)(bpy)](ClO(4))(2) 3, [Ru(bbdo)(bpy)](ClO(4))(2) 4, [Ru(pdto)(dpa)](ClO(4))(2) 5 and [Ru(bbdo)(dpa)](ClO(4))(2) 6 and with the triimine ligand 2,2':6,2''-terpyridine (terpy) to form the unusual seven-coordinate complexes [Ru(pdto)(terpy)](ClO(4))(2) 7 and [Ru(bbdo)(terpy)](ClO(4))(2) 8. In 1 the dimeric cation [Ru(pdto)(mu-Cl)](2)(2+) is made up of two approximately octahedrally coordinated Ru(II) centers bridged by two chloride ions, which constitute a common edge between the two Ru(II) octahedra. Each ruthenium is coordinated also to two pyridine nitrogen and two thioether sulfur atoms of the tetradentate ligand. The ligand pdto is folded around Ru(II) as a result of the cis-dichloro coordination, which corresponds to a "cis-alpha" configuration [DeltaDelta/LambdaLambda(rac) diastereoisomer] supporting the possibility of some attractive pi-stacking interactions between the parallel py rings at each ruthenium atom. The ruthenium atom in the complex cations 3a and 4 exhibit a distorted octahedral coordination geometry composed of two nitrogen atoms of the bpy and the two thioether sulfur and two py/bzim nitrogen atoms of the pdto/bbdo ligand, which is actually folded around Ru(II) to give a "cis-alpha" isomer. The molecule of complex 5 contains a six-coordinated ruthenium atom chelated by pdto and dpa ligands in the expected distorted octahedral fashion. The (1)H and (13)C NMR spectral data of the complexes throw light on the nature of metal-ligand bonding and the conformations of the chelate rings, which indicates that the dithioether ligands maintain their tendency to fold themselves even in solution. The bis-mu-chloro dimers 1 and 2 show a spin-allowed but Laporte-forbidden t(2g)(6)((1)A(1g))--> t(2g)(5) e(g)(1)((1)T(1g), (1)T(2g)) d-d transition. They also display an intense Ru(II) dpi--> py/bzim (pi*) metal-to-ligand charge transfer (MLCT) transition. The mononuclear complexes 3-8 exhibit dpi-->pi* MLCT transitions in the range 340-450 nm. The binuclear complexes 1 and 2 exhibit a ligand field ((3)MC) luminescence even at room temperature, whereas the mononuclear complexes 3 and 4 show a ligand based radical anion ((3)MLCT) luminescence. The binuclear complexes 1 and 2 undergo two successive oxidation processes corresponding to successive Ru(II)/Ru(III) couples, affording a stable mixed-valence Ru(II)Ru(III) state (K(c): 1, 3.97 x 10(6); 2, 1.10 x 10(6)). The mononuclear complexes 3-7 exhibit only one while 8 shows two quasi-reversible metal-based oxidative processes. The coordinated 'soft' thioether raises the redox potentials significantly by stabilising the 'soft' Ru(II) oxidation state. One or two ligand-based reduction processes were also observed for the mononuclear complexes.

Trans-trans-trans-Bis(benzyl isocyanide-κC)dichlorobis(triphenylphosphine-κP)ruthenium(II) dichloromethane solvate

The title compound, [RuCl2(C8H7N)2(C18H15P)2]·CH2Cl2, exhibits the regular octahedral geometry expected for a six-coordinate ruthenium(II) complex. There are two crystallographically independent halves of organometallic mol­ecules in the asymmetric unit, with each metal atom residing on an inversion centre.

Synthetic and mechanistic studies on ruthenium dicarbonyl complexes containing PhP(CH 2CH 2CH 2PCy 2) 2 (Cyttp) ligand

A synthetic and mechanistic study is reported on ligand substitution and other reactions of six-coordinate ruthenium(II) carbonyl complexes containing tridentate PhP(CH 2CH 2CH 2PCy 2) 2 (Cyttp). Carbonylation of cis-mer-Ru(OSO 2CF 3) 2(CO)(Cyttp) ( 1) affords [ cis-mer-Ru(OSO 2CF 3)(CO) 2(Cyttp)]O 3SCF 3 ( 2(O 3SCF 3)) and, on longer reaction times, [ cis-mer-Ru(solvent)(CO) 2(Cyttp)](O 3SCF 3) 2 (solvent = acetone, THF, methanol). 2(O 3SCF 3) reacts with each of NaF, LiCl, LiBr, NaI, and LiHBEt 3 to yield [ cis-mer-RuX(CO) 2(Cyttp)] + (X = F ( 3), Cl ( 4), Br ( 5), I ( 6), H ( 7)), isolated as 3– 7(BPh 4). These conversions proceed with high stereospecificity to afford only a single isomer of the product that is assigned a structure in which the Ph group of Cyttp points toward the CO trans to X ( anti when X = F, Cl, Br, or I; syn when X = H). Treatment of 2(O 3SCF 3) with NaOMe and CO generates the methoxycarbonyl complex [ cis-mer-Ru(CO 2Me)(CO) 2(Cyttp)] + ( 8), whereas addition of excess n-BuLi to 2(O 3SCF 3) in THF under CO affords mer-Ru(CO) 2(Cyttp) ( 9). The two 13C isotopomers [ cis-mer-Ru(OSO 2CF 3)(CO)( 13CO)(Cyttp)]O 3SCF 3 ( 2′(O 3SCF 3): 13CO trans to P C; 2″(O 3SCF 3): 13CO cis to all P donors) were synthesized by appropriate adaptations of known transformations and used in mechanistic studies of reactions with each of LiHBEt 3, NaOMe/CO, and n-BuLi. Whereas LiHBEt 3 reacts with 2′(O 3SCF 3) and 2″(O 3SCF 3) to replace triflate by hydride without any scrambling of the carbonyl ligands, the corresponding reactions of NaOMe–CO are more complex. The methoxide combines with the CO cis to triflate in 2, and the resultant methoxycarbonyl ligand ends up positioned trans to the incoming CO in 8. A mechanism is proposed for this transformation. Finally, treatment of either 2′(O 3SCF 3) or 2″(O 3SCF 3) with an excess of n-BuLi leads to the formation of the same two ruthenium(0) isomers of mer-Ru(CO)( 13CO)(Cyttp). These products represent, to our knowledge, the first example of a syn–anti pair of isomers of a five-coordinate metal complex.

A study of syn–anti isomerism of six-coordinate ruthenium(II) complexes containing PhP(CH2CH2CH2PCy2)2 (Cyttp) ligand

Abstract A study is reported on synthesis and ligand substitution/modification reactions of the syn and anti geometric isomers of the six-coordinate ruthenium(II) complexes [mer-Ru(κ2-O2CX)(CO)(Cyttp)]n (n = 0, X = O (2); n = +1, X = Me (3), Ph (4), OMe (5), OEt (6); Cyttp = PhP(CH2CH2CH2PCy2)2) and cis-mer-RuX2(CO)(Cyttp) (X = I (7), Cl (8)) (syn (s) and anti (a) refer to the orientation of the Ph group on the central P atom of Cyttp). Reaction of cis-mer-Ru(BF4)2(CO)(Cyttp) (1) in freshly prepared aqueous acetone solution with each of sodium carbonate, sodium acetate, and sodium benzoate affords 2a, 3a(BF4), and 4a(BF4), respectively. The syn isomer of 2a, 2s, was synthesized by prolonged treatment of solid mer-Ru(CO)2(Cyttp) with gaseous O2. Complexes 2a and 2s do not interconvert even on heating in toluene or methanol at reflux temperature for 24 h. Alkylation of 2a and 2s with 1 equiv. of [Me3O]BF4 or [Et3O]PF6 affords the methylcarbonato (5a(BF4) and 5s(BF4), respectively) and ethylcarbonato (6a(PF6) and 6s(PF6), respectively) complexes. Use of >2 equiv. of [Me3O]BF4 still furnishes 5s(BF4) from 2s, but yields 1 instead of 5a(BF4) from 2a. The foregoing reactions represent, to our knowledge, the first example of different reactivity of syn and anti isomers of metal Cyttp complexes. Prolonged treatment of 2a with an excess of MeI at room temperature results in the formation of 7a. A parallel reaction of 2s with MeI to yield 7s requires heating; at ambient temperature, 5s(I) is obtained instead. Each of the complexes 2, 3(BF4)–5(BF4), and 6(PF6) is converted to 8 with retention of the syn or anti configuration by the action of hydrochloric acid. It is concluded from this and previous studies that complexes stable to ligand dissociation do not undergo syn–anti isomerization, in contrast to those that contain weakly coordinated ligands. 13C{1H} and 31P{1H} NMR spectroscopic generalizations were developed that enable syn–anti assignment to be made for this class of complexes. The structures of 2a (as 2a·CH2Cl2·2H2O), 2s (as 2s·(3/4)MeC(O)Me·2H2O), and 5s (as 5s(BF4)·C6H6) were determined by single crystal X-ray diffraction analysis.

Use of HPLC in the identification of cis and trans-diaquabis(2,2 ′-bipyridine)ruthenium(II) complexes: crystal structure of cis-[Ru(H 2O) 2(bpy) 2](PF 6) 2

[Ru(H 2O) 2(bpy) 2](PF 6) 2 complex was obtained by reacting HPF 6 in a [Ru(CO 3)(bpy) 2] aqueous solution. The complex can exist as cis and trans isomers and usually has been used in the preparation of several ruthenium–bipyridine species. Despite the possibility to have contamination of a specie in another, there is no analytical control involving the characterization of both complexes. Based on this we have proposed the use of high-performance liquid chromatography (HPLC) as an analytical technique to control the purity of cis and trans isomers. The separation was performed using a CLC-ODS column. The cis isomer eluted at 9.4 min while trans isomer eluted at 4.3 min. In aqueous solution the trans and cis isomer configurations were confirmed by NMR spectra ( 1H). The attribution of cis isomer was also made based on the X-ray crystal structure (monoclinic, P2 1/c, a=12.320(2), b=13.852(2), c=34.220(3) Å, β=91.89(1)°, Z=8) which is reported. The six-coordinated ruthenium atom is chelated by two bipyridines and two molecules of H 2O.

Novel ruthenium(ii) complexes containing imino- or aminophosphine ligands for catalytic transfer hydrogenation

Five- and six-coordinate ruthenium(II) complexes containing imino- and aminophosphines have been prepared by ligand exchange processes. Thus, reactions of [RuCl2(PPh3)3] with 2-Ph2PC6H4CHNR (R = Ph (1a); 2′,6′-C6H3Me2 (1b); 2′-C6H4OMe (1c)) lead to the chelate iminophosphine complexes [RuCl2(κ2-P,N-2-Ph2PC6H4CHNR)(PPh3)] (R = Ph (3a); 2′,6′-C6H3Me2 (3b)) and [RuCl2(κ3-P,N,O-2-Ph2PC6H4CHN-2′-C6H4OMe)(PPh3)] (3c), respectively. Similarly, reactions with aminophosphine ligands 2-Ph2PC6H4CH2NHR (R = Ph (2a); iPr (2d); (S)-CHMeCy (2e)) afford the 16-electron complexes [RuCl2(κ2-P,N-2-Ph2PC6H4CH2NHR)(PPh3)] (R = Ph (5a); iPr (5d); (S)-CHMeCy (5e)). The iminophosphines 2-Ph2PC6H4CHNR (R = iPr (1d); (S)-CHMeCy (1e)) react with [RuCl2(DMSO)4] to lead to the bis-iminophosphine complexes [RuCl2(κ2-P,N-2-Ph2PC6H4CHNR)2] (R = iPr (4d); (S)-CHMeCy (4e)). The crystal structure of 4d has been determined by X-ray diffraction. Complexes 3a–c, 4d,e and 5a,d,e are active in catalytic transfer hydrogenation of acetophenone. All of them are more efficient than the precursor [RuCl2(PPh3)3].