Ruthenium Carbonyl Research Articles

Flexible Modulation of CO-Release Using Various Nuclearity of Metal Carbonyl Clusters on Graphene Oxide for Stroke Remediation.

Utilizing the size-dependent adsorption properties of ruthenium carbonyl clusters (Ru-carbon monoxide (CO)) onto graphene oxide (GO), a facile CO-release platform for in situ vasodilation as a treatment for stroke-related vascular diseases is developed. The rate and amount of formation of the CO-release-active RuII (CO)2 species can be modulated by a simple mixing procedure at room temperature. The subsequent thermally induced oxidation of RuII (CO)2 to RuO2 on the GO surface results in the release of CO. Further modulation of thermal and CO-release properties can be achieved via a hybridization of medium- and high-nuclearity of Ru-CO clusters that produces a RuO2 /RuII (CO)2 /6 Ru-CO-GO composite, where 6 Ru-CO-GO provides a photothermally activated reservoir of RuII (CO)2 species and the combined infrared absorption properties of GO and RuO2 provides photothermal response for in situ CO-release. The RuO2 /RuII (CO)2 /6 Ru-CO-GO composite does not produce any cytotoxicity and the efficacy of the composite is further demonstrated in a cortical photothrombotic ischemia rat model.

A rapid and highly sensitive strain-effect graphene-based bio-sensor for the detection of stroke and cancer bio-markers.

Here, we propose a highly sensitive and rapid bio-sensor for the detection of bio-markers for stroke and cancer-related diseases, based on the utilization of the adsorption properties of ruthenium carbonyl (Ru-CO) clusters on monolayer graphene (MG). A fast rate of decarbonylation of Ru-CO to form ruthenium oxide nanoparticles (RuO2 NPs) on MG was observed. The quantitative detection of matrix metalloproteinase-2 (MMP-2) (bio-marker for stroke and vascular diseases) was demonstrated by tracking the spectral shift of the characteristic G band of graphene caused by the adsorption of RuO2 NPs. A concentration as low as 17 ng mL-1 of MMP-2 was detected in a simulated clinical serum sample. This effective bio-sensor has the potential to revolutionize the biomedical field in the early detection and possible prevention of stroke and cancer diagnosis.

Ruthenium carbonyl complexes with pyridylalkanol ligands: synthesis, characterization and catalytic properties for aerobic oxidation of secondary alcohols

Several new trinuclear ruthenium carbonyl complexes were synthesized and their application in aerobic oxidation of secondary alcohols was also established.

Ruthenium carbonyl complexes with pyridine-alkoxide ligands: synthesis, characterization and catalytic application in dehydrogenative oxidation of alcohols

Dehydrogenative oxidation of secondary alcohols catalyzed by several new trinuclear ruthenium carbonyl complexes under mild conditions was proposed.

Decarboxylation of Fatty Acids with Triruthenium Dodecacarbonyl: Influence of the Compound Structure and Analysis of the Product Mixtures.

Recently, the decarboxylation of oleic acid (9(Z)-octadecenoic acid) catalyzed by triruthenium dodecacarbonyl, Ru3(CO)12, to give a mixture of heptadecenes with concomitant formation of other hydrocarbons, heptadecane and C17 alkylbenzenes, was reported. The product mixture, consisting of about 77% heptadecene isomers, 18% heptadecane, and slightly >4% C17 alkylbenzenes, possesses acceptable diesel fuel properties. This reaction is now applied to other fatty acids of varying chain length and degree of saturation as well as double-bond configuration and position. Acids beyond oleic acid included in the present study are lauric (dodecanoic), myristic (tetradecanoic), palmitic (hexadecanoic), stearic (octadecanoic), petroselinic (6(Z)-octadecenoic), elaidic (9(E)-octadecenoic), asclepic (11(Z)-octadecenoic), and linoleic (9(Z),12(Z)-octadecadienoic) acids. Regardless of the chain length and degree of unsaturation, a similar product mixture was obtained in all cases with a mixture of alkenes predominating. Monounsaturated fatty acids, however, afforded the alkane with one carbon less than the parent fatty acid as the most prominent component in the mixture. Alkylbenzenes with one carbon atom less than the parent fatty acid were also present in all product mixtures. The number of isomeric alkenes and alkylbenzenes depends on the number of carbons in the chain of the parent fatty acid. With linoleic acid as the starting material, the amount of alkane was reduced significantly with alkenes and alkylaromatics enhanced compared to the monounsaturated fatty acids. Two alkenes, 9(E)-tetradecene and 1-hexadecene, were also studied as starting materials. A similar product mixture was observed but with comparatively minor amount of alkane formed and alkene isomers dominating at almost 90%. The double-bond position and configuration in the starting material do not influence the pattern of alkene isomers in the product mixture. The results underscore the multifunctionality of the Ru3(CO)12 catalyst, which promotes a reaction sequence including decarboxylation, isomerization, desaturation, hydrogenation, and cyclization (aromatization) to give a mixture of hydrocarbons simulating petrodiesel fuels. A reaction pathway is proposed to explain the existence of these products, in which alkenes are dehydrogenated to alkadienes and then, under cyclization, to the observed alkylaromatics. The liberated hydrogen can then saturate alkenes to the corresponding alkane.

Coordinatively Labile 18-Electron Arene Ruthenium Iminophosphonamide Complexes.

The thermodynamics of chloride dissociation from the 18e arene ruthenium iminophosphonamides [(η6 -arene)RuCl{(R'N)2 PR2 }] (1 a-d) [previously known with arene=C6 Me6 , R=Ph, R'=p-Tol (a); R=Et, R'=p-Tol (b); R=Ph, R'=Me (c); and new with arene=p-cymene, R=Ph, R'=p-Tol (d)] was assessed in both polar and apolar solvents by variable-temperature UV/Vis, NMR, and 2D EXSY 1 H NMR methods, which highlighted the influence of the NPN ligand on the equilibrium parameters. The dissociation enthalpy ΔHd decreases with increasing electron-donating ability of the N- and P-substituents (1 a, 1 d>1 b>1 c) and solvent polarity, and this results in exothermic spontaneous dissociation of 1 c in polar solvents. The coordination of neutral ligands (MeCN, pyridine, CO) to the corresponding 16e complexes [(η6 -arene)Ru{(R'N)2 PR2 }]+ PF6- (2 a-d) is reversible; the stability of the 2⋅L adducts depends on the π-accepting ability of L. Carbonylation of 2 a and 2 d resulted in rare examples of cationic arene ruthenium carbonyl complexes (3 a, 3 d), while the monocarbonyl adduct derived from 2 c reacts further with a second equivalent of CO with conversion to carbonyl-carbamoyl complex 3 c, in which one CO molecule is inserted into the Ru-N bond. The new complexes 1 d, 2 d, 3 a, 3 c, and 3 d were isolated and structurally characterized.

β‐Diketiminato–Germylene Complexes of Carbonyl Ruthenium: Synthesis, Structure, and Reactivity

The reaction of the β‐diketiminatochlorogermylene L(Cl)Ge {1, L = HC[C(Me)N‐2,6‐iPr2C6H3]2} with Ru3(CO)12 in molar ratios of 3:1 or 6:1 led to the Ge2Ru complex [L(Cl)Ge]2Ru(CO)3 (3). A speculative GeRu intermediate, L(Cl)GeRu(CO)4, was detected when the reaction was monitored by 1H NMR spectroscopy at elevated temperatures. The formation of this intermediate was supported by similar monitoring of the reaction of L(PhC≡C)Ge (2) with Ru3(CO)12 by 1H NMR spectroscopy and the isolation of a mixture of L(PhC≡C)GeRu(CO)4 (4) and [L(R)Ge]2Ru(CO)3 (5) from this reaction in a molar ratio of 3:1 as well as the clean formation of 5 from such a reaction in a 6:1 molar ratio. Complex 3 reacted with LiHBEt3 through an unusual Cl/Et metathesis to give L(Et)GeRu(CO)4 (6). However, the reaction of 3 with LiN(SiMe3)2 resulted in the base‐assisted dehydrochlorination involving one methyl group of each L ligand backbone and the chlorine atom at the Ge center to yield [L′Ge]2Ru(CO)3 {7, L′ = HC[C(Me)N‐2,6‐iPr2C6H3][C(CH2)N‐2,6‐iPr2C6H3]}. The further reaction of 7 with a stoichiometric amount of H2O afforded L(HO)GeRu(CO)4 (8) through a 1,4‐dipolar addition across the L′Ge functionality. In addition, the reaction of 3 with I2 occurred through an oxidative addition at the Ru center to generate L(Cl)GeRuI2(CO)3 (10).

Efficient and versatile catalysis for β-alkylation of secondary alcohols through hydrogen auto transfer process with newly designed ruthenium(II) complexes containing ON donor aldazine ligands

A new series of ruthenium(II) carbonyl complexes, [RuCl(CO)(EPh3)2(L1-2)] (1–4) (E = P or As; H2L1 = salicylaldazine, H2L2 = 2-hydroxynaphthaldazine), have been assembled from ruthenium(II) precursors [RuHCl(CO)(EPh3)3] and bidentate ON donor Schiff base ligands (H2L1-2). Both ligands and their new ruthenium(II) complexes have been characterized by elemental analyses, spectroscopic methods (UV, IR, NMR (1H, 13C, 31P) as well as ESI mass spectrometry. The molecular structures of H2L1 and 1 have been confirmed by single crystal X-ray diffraction. Based on the above studies, an octahedral coordination geometry around the metal center has been proposed for 1–4. To investigate the catalytic effectiveness of 1–4, the complexes have been used as catalysts in β-alkylation of secondary alcohols with primary alcohols and synthesis of quinolines. The effect of solvent, time, base, catalyst loading, and substituent of the ligand moiety on the reaction was studied. Notably, 1 was a more efficient catalyst toward alkylation of a wide range of alcohols and quinolines synthesis. The reusability of the catalyst was checked and the results showed up to six catalytic runs without significant loss of activity.

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.

Urinary tract infection fighting potential of Newly synthesized ruthenium carbonyl complex of N-dehydroacetic acid-N′-o-vanillin-ethylenediamine

In recent years, there has been a growing fascination towards the development of new antimicrobial agents from various sources to combat microbial resistance. Klebsiella pneumonia and E. coli are the main urinary tract infection (UTI) causing agents. Herein, we report the synthesis and characterization of a novel carbonyl complex of Ru(II) that has been found a good antimicrobial agent against the selected microbes. Hence, may be suggested as potent agent against UTI. The compound on characterization was found octahedral in structure on the basis of comparative DFT-experimental characterization. Molecular specification under B3LYP functional, LANL2DZ basis set for Ru atom and 6-31g(d,p) for all other atoms were employed. Electron density plots and geometrical optimization were the main theoretical aspects that were invoked. Elemental analysis, mass spectrometry, NMR, FT-IR, UV–Vis and cyclic voltammetry were the physio-chemical techniques at both the experimental and theoretical fronts that helped to establish the proposed structure. From the overall study, it may be remarked that both observed and computed outcomes have been found in good agreement with each other.

Synthesis, Properties, and Reactivities of Ruthenium(II) Carbonyl 5,15-Diazaporphyrins

We have succeeded in the synthesis of ruthenium(II) carbonyl 5,15-diazaporphyrin complexes 2 having pyridines as axial ligands. The structures, properties, and reactivities under photoirradiation of 2 are compared with those of the corresponding ruthenium porphyrins.

Strong Interaction of Ruthenium Species with Graphite Structure for the Self-Dispersion of Ru under Solvent-Free Conditions

Carbon materials-supported Ru catalysts are some of the most efficient catalysts for ammonia synthesis. Usually they are prepared by impregnation for the dispersion of the Ru metal. In the present study, we report that a strong interaction of ruthenium species (with triruthenium dodecacarbonyl as the precursor) with a graphite structure enables the self-dispersion of Ru under solvent-free conditions. Via simple mixing and heat treatment, sub-nano Ru particles over high surface area graphite (HSAG) are obtained with uniform distribution. The ammonia yields or ammonia synthesis rate is almost 50% higher than the catalysts prepared via impregnation whether the support is activated carbon or HSAG. During catalyst preparation, Ru3(CO)12 is adsorbed on the surface of HSAG via CO groups in Ru3(CO)12 and surface oxygen groups on HSAG. Subsequently, Ru3(CO)12 undergoes decarbonylation reaction at very low temperatures. Then, CO has a dismutation reaction over the Ru surface leading to the formation of RuO2 at temp...

High-nuclearity ruthenium carbonyl cluster chemistry. 9. Ligand substitution at decaruthenium carbonyl clusters

The mono- to tri-substituted decaruthenium cluster anions [Ru10(μ-H)(μ6-C)(CO)24–x(L)x]- [L = P(C6H4Me-4)3, AsPh3, SbPh3, x = 1–3] were prepared as their [PPh4]+ salts in moderate to good yields from reaction of [PPh4][Ru10(μ-H)(μ6-C)(CO)24] with the corresponding group 15 ligands at room temperature in acetone. The tetrakis-substituted cluster Ru10(μ6-C)(μ3-CO)(μ-CO)(CO)19{P(C6H4Me-4)3}4 was obtained in high yield from [PPh4]2[Ru10(μ6–C)(CO)24] and an excess of the phosphine under the same conditions; a single-crystal X-ray diffraction study revealed that the phosphines ligate at the vertices of the “giant tetrahedral” core. Kinetics studies of the formation of [PPh4][Ru10(μ-H)(μ6-C)(AsPh3)2(CO)22] from [PPh4][Ru10(μ-H)(μ6-C)(AsPh3)(CO)23] shows that ligand substitution at these giant tetrahedral clusters proceeds via a strongly associative pathway with the likely intermediacy of a Ru-Ru bond-cleaved intermediate.

Studies of Carbon Monoxide Release from Ruthenium(II) Bipyridine Carbonyl Complexes upon UV-Light Exposure.

The UV-light-induced CO release characteristics of a series of ruthenium(II) carbonyl complexes of the form trans-Cl[RuLCl2(CO)2] (L = 4,4'-dimethyl-2,2'-bipyridine, 4'-methyl-2,2'-bipyridine-4-carboxylic acid, or 2,2'-bipyridine-4,4'-dicarboxylic acid) have been elucidated using a combination of UV-vis absorbance and Fourier transform infrared spectroscopies, multivariate curve resolution alternating least-squares analysis, and density functional theory calculations. In acetonitrile, photolysis appears to proceed via a serial three-step mechanism involving the sequential formation of [RuL(CO)(CH3CN)Cl2], [RuL(CH3CN)2Cl2], and [RuL(CH3CN)3Cl]+. Release of the first CO molecule occurs quickly (k1 ≫ 3 min-1), while release of the second CO molecule proceeds at a much more modest rate (k2 = 0.099-0.17 min-1) and is slowed by the presence of electron-withdrawing carboxyl substituents on the bipyridine ligand. In aqueous media (1% dimethyl sulfoxide in H2O), the two photodecarbonylation steps proceed much more slowly (k1 = 0.46-1.3 min-1 and k2 = 0.026-0.035 min-1, respectively) and the influence of the carboxyl groups is less pronounced. These results have implications for the design of new light-responsive CO-releasing molecules ("photoCORMs") intended for future medical use.

Biomolecular interaction and in vitro cytotoxicity of ruthenium complexes containing heterocyclic hydrazone. Is methanol a non-innocent solvent to influence the oxidation state of the metal and ligation of hydrazone?

Two new stable ruthenium complexes, [RuIII(HL)Cl2(PPh3)2] (1) and [RuII(L)(CO)(PPh3)2] (2), were synthesized from the reaction of [RuIIICl3(PPh3)3] with thiophene-2-carboxylic acid (2-hydroxyl-benzylidene)-hydrazide (H2L) in chloroform–methanol. Surprisingly, the same reaction performed by adding KOH to the reaction medium resulted in the exclusive formation of the bivalent ruthenium carbonyl complex 2. Both complexes 1 and 2 were characterized by elemental analysis, EPR/NMR and single crystal X-ray diffraction study. From the DNA binding and quenching experiments, an intercalative mode of binding with DNA was identified. The DNA cleavage activity of the complexes, monitored using gel electrophoresis, showed significant damage of the plasmid DNA. Bovine serum albumin (BSA) binding capabilities analysed using absorption and emission spectroscopic methods showed a strong binding interaction of complexes 1 and 2 with BSA. The in vitro cytotoxicity studied against human breast cancer cell models (MCF-7 and MDAMB-453) showed that complex 1 possessed activity comparable to that of the standard positive reference cisplatin. The IC50 concentration of complexes treated with cancer cell models exhibited a significant increase in lactate dehydrogenase release and nitrite content in the culture medium. Overall, the trivalent ruthenium hydrazone complex 1 exhibited better activity towards biomolecules and cancer cells than complex 2.

Ruthenium(II) carbonyl compounds with the 4'-chloro-2,2':6',2''-terpyridine ligand.

Two ruthenium carbonyl complexes with the 4'-chloro-2,2':6',2''-terpyridine ligand (tpy-Cl, C15H10ClN3), i.e. [RuCl(tpy-Cl)(CO)2][RuCl3(CO)3] (I) [systematic name: cis-di-carbonyl-chlorido(4'-chloro-2,2':6',2''-terpyridine-κ3N)ruthenium(II) fac-tricarbonyltri-chlorido-ruthenate(II)], and [RuCl2(tpy-Cl)(CO)2] (II) [cis-dicarbonyl-trans-di-chlorido(4'-chloro-2,2':6',2''-terpyridine-κ2N1,N1')ruthenium(II)], were synthesized and characterized by single-crystal X-ray diffraction. The RuII atoms in both centrosymmetric structures (I) and (II) display similar, slightly distorted octa-hedral coordination spheres. The coordination sphere in the complex cation in compound (I) is defined by three N atoms of the tridentate tpy-Cl ligand, two carbonyl carbon atoms and one chlorido ligand; the charge is balanced by an octa-hedral [Ru(CO)3Cl3]- counter-anion. In the neutral compound (II), the tpy-Cl ligand coordinates to the metal only through two of its N atoms. The coordination sphere of the RuII atom is completed by two carbonyl and two chlorido ligands. In the crystal structures of both (I) and (II), weak C-H⋯Cl inter-actions are observed.

Polybutylene terephthalate reactive blending with polymethylhydrosiloxane by ruthenium‐catalyzed carbonyl hydrosilylation reaction

ABSTRACTCarbonyl hydrosilylation reaction was developed to prepare reactive blending between PBT and polymethylhydrosiloxane (PMHS). It focused on the addition reaction of Si–H groups from PMHS onto carbonyl groups from PBT catalyzed by triruthenium dodecacarbonyl (Ru3(CO)12). An approach on PBT model compounds was carried out and investigated by NMR spectroscopy to evidence the potentiality and efficiency of carbonyl hydrosilylation reaction. At temperatures up to 100 °C, the hydrosilylation reaction can reach 33 mol% conversion in a few hours. Side reactions were also highlighted. Such side reactions can reach more than 23 mol% of the final products when temperature increases to 180 °C. Then hydrosilylation reaction was extended to PBT modification with a molar ratio of ester group/SiH = 3.5 and viscosity ratio polysiloxane/PBT = 4.0 × 10−5. The reaction was carried out in an internal mixer at 220 °C and followed through the evolution of the torque of the reactional medium. Samples for different processing times were investigated by SEM and rheology. From these analyses, the dispersion of PMHS was promoted with diameters of few micrometers. The elastic behavior of final material was characteristic of solid or gel‐like structures, suggesting a network structure formation consistent with the gel fraction increase from 0 to 0.55. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1855–1868

Synthesis and Structures of NCN Pincer-Type Ruthenium and Iridium Complexes Bearing Protic Pyrazole Arms

The reaction of the 1,3-bis(pyrazol-3-yl)benzenes 1 with [RuCl(OAc)(PPh3)3] resulted in selective C–H cleavage at the 2-position of 1 to give the protic NCN pincer-type ruthenium(II) complexes [RuCl(R-NCN-LH2)(PPh3)2] (2; R-NCN-LH2 = 4-R-2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)phenyl). Similar cyclometalation with iridium trichloride followed by addition of triphenylphosphine led to the formation of the iridium(III) analogue [IrCl(But-NCN-LH2)(PPh3)]Cl (5). Treatment of the ruthenium complexes 2 with carbon monoxide afforded the carbonyl complexes [Ru(CO)(R-NCN-LH2)(PPh3)2]Cl (4). On the other hand, the pyridine analogue of 1, 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine (NNN-LH2), reacted with iridium trichloride to yield the protic NNN pincer-type complex [IrCl3(NNN-LH3)] (7). The stronger σ donation of the NCN pincer-type ligand in comparison with the analogous NNN ligand was suggested by the CO stretching frequencies of the ruthenium carbonyl complexes 4 as well as the M–Cl distances. The catalytic acti...

Biobased Methacrylic Acid via Selective Catalytic Decarboxylation of Itaconic Acid

We report a biobased route to methacrylic acid via selective decarboxylation of itaconic acid utilizing catalytic ruthenium carbonyl propionate in an aqueous solvent system. High selectivity (>90%) was achieved at low catalyst loading (0.1 mol %) with high substrate concentration (5.5 M) at low temperature (200–225 °C) and pressure (≤425 psig) relative to previous contributions in this area. Direct decarboxylation of itaconic acid was achieved as opposed to the conjugate base reported previously, thereby avoiding basification and acidification steps. Also investigated was catalytic manganese(II) oxalate (5 mol %), but low yield (4.8%) and evolution of carbon monoxide via oxalate decomposition was problematic. Attempts at stabilization of the catalyst with triphenylphosphine were unsuccessful, but it exhibited greater catalytic efficacy (14.0% yield) than the manganese catalyst (4.8% yield) at 5 mol %. Neither carbon monoxide nor propylene (excessive decarboxylation) were detected during ruthenium-catalyze...

Synthesis, characterization, X-ray crystallography and stability in aqueous medium of trans-[Ru(CO)(NH3)4P(OH)3]2+

Here, we report the synthesis, characterization, crystal data and DFT calculation of a new water-soluble ruthenium(II) carbonyl complex. The trans-[Ru(CO)(NH3)4P(O)(OH)2]Cl is a robust complex in aqueous media. The pKa of 3.3 for the phosphorous acid ligand in this complex was measured by infrared spectroscopy. The trans-[Ru(CO)(NH3)4P(O)(OH)2]+ exhibits just two slow reactions at pH 7.5: CO–Ru–P(O)(OH)2 to CO–Ru–(O)P(OH)2 isomerization (k=1.1×10−5s−1 at 25°C) and subsequent P(O)(OH)2 dissociation (k=1.7×10−7s−1 at 25°C). The formation of O-bonded trans-[Ru(CO)(NH3)4(O)P(OH)2]+ was supported by IR, UV–Vis and 31P NMR spectroscopies and DFT calculations.