Amidinate Complexes Research Articles

Reversible Grafting in Surface Organometallic Chemistry with a Late Transition‐Metal Amidinate Precursor

Supported catalysts are central to industrial catalytic processes. While traditional synthesis methods often yield poorly defined materials, thus complicating structural elucidation, Surface Organometallic Chemistry (SOMC) offers a solution, producing well‐defined structures. Recent advances in SOMC precursor development have shown that amidinate‐based precursors are a privileged class of precursors to generate supported metallic nanoparticles. In that context, this study investigates the grafting mechanism of a prototypical amidinate precursor, Ir(COD)(DIA) (1‐Ir), onto SiO2. Unique to amidinate complexes, grafting is shown to occur without ligand release, creating a reversible covalent bond. Using Ir‐TBOS as a molecular analogue, the structure of the grafted species and the reversibility of the reaction with O‐H groups are demonstrated using IR spectroscopy, single X‐Ray diffraction, variable‐temperature NMR spectroscopy, X‐Ray absorption spectroscopy (XAS), and supported by DFT calculations. Notably, we show that a partial degrafting is also possible at elevated temperatures under vacuum

Structure, Covalency, and Paramagnetism of Homoleptic Actinide and Lanthanide Amidinate Complexes.

Isostructural trivalent lanthanide and actinide amidinates bearing the N,N'-bis(isopropyl)benzamidinate (iPr2BA) ligand [LnIII/AnIII(iPr2BA)3] (Ln = La, Nd, Sm, Eu, Yb, Lu; An = U, Np) have been synthesized and characterized in both solid and solution states. All compounds were examined in the solid state utilizing single crystal X-ray diffraction (SC-XRD), revealing a notable deviation in the actinide series with shortened bond lengths compared to the trend in the lanthanide series, suggesting a nonionic contribution to the actinide-ligand bonding. Quantum-chemical bonding analysis further elucidated the nature of these interactions, highlighting increased covalency within the actinide series, as evidenced by higher delocalization indices and greater 5f orbital occupation, except for Th(III) and Pa(III), which demonstrated substantial 6d orbital occupancies. An in-depth paramagnetic NMR study in solution also sheds light on the covalent character of actinide-ligand bonding, with the separation of pseudocontact (PCS) and contact shift (FCS) contributions employing the Bleaney and Reilley method. This analysis unveiled significant contact contributions in the actinide complexes, indicating enhanced covalency in actinide-ligand bonding. To corroborate these observations, an accurate PCS calculation method based on the Kuprov equation, incorporating both the distribution of electronic spin density and magnetic susceptibility obtained from CASSCF calculations, was applied and compared with experimental values.

Kinetic and Thermodynamic Pathways in the Reactions of Five-Membered Zircona- and Hafnacyclocumulenes with Acetonitrile. Structures and Mechanisms of Formation of the Obtained Complexes

The heating of five-membered zircona- and hafnacyclocumulene complexes (7) with a 2-fold excess of acetonitrile results in the formation of dimeric metallaazacyclopentadiene complexes (6), bicyclic amidine complexes (5), and tricyclic metallacycles (2). These three classes of compounds can be considered as kinetically (6) and thermodynamically (2 and 5) favorable products, the yield of which depends on both the process conditions and the structure of the initial complexes. On the basis of experimental and theoretical data, for all three types of products the reaction proceeds through the formation of monomeric metallaazacyclopentadienes (4) that are competitive.

Ferromagnetic Ni Nanoparticle with Controlled Anisotropy: From Polyhedral to Planar Tetrapods

Liquid phase syntheses mainly yield nanoparticles with compact shapes, such as spheres or cubes. However, controlling not only the size but also the shape of magnetic nanoparticles would enable a fine-tuning of their intrinsic properties, due to the shape anisotropy induced by long-range dipolar interactions. We report here a fairly simple approach based on the reduction of an amidinate complex in the presence of a mixture of long-chains acid and amine to yield ferromagnetic Ni nanoparticles. The formation of stable Ni complexes could be promoted in situ by increasing the acid concentration, thus allowing tuning of the final particle size. While amine could be used as a soft reducing agent, dihydrogen was essential to promote anisotropic shapes. Electron holography combined with micromagnetic simulations showed that the resulting shape anisotropy could impose complex magnetic configurations within planar tetrapods. Regarding the heating efficiency, which directly scales with the magnetic hysteresis loop area, maxima of 100W·g–1 were found for nanoplates and nanorods, opening promising perspectives for magnetically induced catalysis.

Synthesis and Complexation Study of New Aminoalkynyl−amidinate Ligands

AbstractThe current library of amidinate ligands has been extended by the synthesis of two novel dimethylamino‐substituted alkynylamidinate anions of the composition [Me2N−CH2−C≡C−C(NR)2]−(R =iPr, cyclohexyl (Cy)). The unsolvated lithium derivatives Li[Me2N−CH2−C≡C−C(NR)2] (1: R =iPr,2: R = Cy) were obtained in good yields by treatment ofin situ‐prepared Me2N−CH2−C≡C−Li with the respective carbodiimides, R−N=C=N−R. Recrystallization of1and2from THF afforded the crystalline THF adducts Li[Me2N−CH2−C≡C−C(NR)2] ⋅ nTHF (1 a: R =iPr,n=1;2 a: R = Cy,n=1.5). Precursor2was subsequently used to study initial complexation reactions with selected di‐ and trivalent transition metals. The dark red homoleptic vanadium(III) tris(alkynylamidinate) complex V[Me2N−CH2−C≡C−C(NCy)2]3(3) was prepared by reaction of VCl3(THF)3with 3 equiv. of2(75 % yield). A salt‐metathesis reaction of2with anhydrous FeCl2in a molar ratio of 2 : 1 afforded the dinuclear homoleptic iron(II) alkynylamidinate complex Fe2[Me2N−CH2−C≡C−C(NCy)2]4(4) in 69 % isolated yield. Similarly, treatment of Mo2(OAc)4with 3 or 4 equiv. of2provided the dinuclear, heteroleptic molybdenum(II) amidinate complex Mo2(OAc)[Me2N−CH2−C≡C−C(NCy)2]3(5; yellow crystals, 50 % isolated yield). The cyclohexyl‐substituted title compounds2 a,4, and5were structurally characterized through single‐crystal X‐ray diffraction studies.

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

Hydrogen bonds and dispersion forces serving as molecular locks for tailored Group 11 bis(amidine) complexes

A flexible polydentate bis(amidine) ligand operates as a molecular lock for CuCl, AgCl, AuCl, and AuMes fragments by forming flexible double macrocycles with N–H⋯R–M hydrogen bonds and additional distinct weak intramolecular forces.

Luminescent early-late-hetero-tetranuclear group IV - Au(I) bisamidinate complexes.

The versatile metalloligand [{HCCC(NDipp)2}2Au2] (dipp = 2,6-diisopropylphenyl) was converted into early-late heterotetrametallic complexes [{ClCp2MCCC(NDipp)2}2Au2] (M = Ti, Zr). These compounds show photoluminescence with either remarkably different (Ti) or similar (Zr) features as compared to related solely coinage metal containing acetylide amidinate complexes.

Bis(alkyl) Sc and Y Complexes Supported by Tri‐ and Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in α‐Olefin and Isoprene Polymerization

AbstractBis(alkyl) complexes [(2,6‐Me2C6H3)NC(tBu)N(C6H4−2‐OMe)]M(CH2C6H4−2‐NMe2)2 (M=Sc (4), Y (5)), [(2‐OMe−C6H4N)2C(tBu)]Y(CH2SiMe3)2(THF)2 (6), supported by N,N,O‐tridentate (4, 5) and N,N,O,O‐tetradentate (6) amidinate ligands were synthesized by the alkane elimination approach reacting tris(alkyl) rare‐earth species M(R)3Xn (R=Me3SiCH2, X=THF, n=2; R=CH2C6H4−2‐NMe2, n=0) with one equivalent of amidine (2,6‐Me2C6H3)N=C(tBu)−NH(C6H4−2‐OMe) (1) or (2‐MeO−C6H4)N=C(tBu)−NH(C6H4−2‐OMe) (2). The reaction of amidine 2 with equimolar amount of Y(CH2C6H4−2‐NMe2)3 in toluene unexpectedly results in the addition of N,N‐dimethylaminobenzyl group to C=N bond of one amidinate fragment, ligand disproportionation and the formation of novel bis(amide)amidinate complex [(2‐OMe−C6H4N)2C(tBu)CH2C6H4−2‐NMe2]Y[(2‐OMe−C6H4N)2C(tBu)] (7). Complexes 4–6 were evaluated as catalysts for α‐olefins and isoprene polymerization.

(tBuN)SiMe2NMe2—A new N,N′-κ2-monoanionic ligand for atomic layer deposition precursors

Eight new atomic layer deposition (ALD) precursors were synthesized using a ligand that is new to the field of ALD: (tBuNH)SiMe2NMe2. Complexes containing Mg, V, Mn, Fe, Co, Ni, and Zn were found to be tetrahedral, and Li complexes form more complex structures. These compounds performed exceptionally well by thermogravimetric analysis (TGA). All compounds except for one Li species and the Fe complex left residual masses below 5%, similar or better than the analogous amidinate complexes. In particular, the Co(II) complex is very thermally robust and performs very well during a TGA stress test, surpassing temperatures above 200 °C. These compounds are the first of a family of precursors containing this type of monoanionic N–Si–N ligand and are prime candidates for ALD process development.

Novel polyamide amidine anthraquinone platinum(II) complexes: cytotoxicity, cellular accumulation, and fluorescence distributions in 2D and 3D cell culture models.

1- and 1,5-Aminoalkylamine substituted anthraquinones (AAQs, 1C3 and 1,5C3) were peptide coupled to 1-, 2-, and 3-pyrrole lexitropsins to generate compounds that incorporated both DNA minor groove and intercalating moieties. The corresponding platinum(II) amidine complexes were synthesized through a synthetically facile amine-to-platinum mediated nitrile 'Click' reaction. The precursors as well as the corresponding platinum(II) complexes were biologically evaluated in 2D monolayer cells and 3D tumour cell models. Despite having cellular accumulation levels that were up to five-fold lower than that of cisplatin, the platinum complexes had cytotoxicities that were only three-fold lower. Accumulation was lowest for the complexes with two or three pyrrole groups, but the latter was the most active of the complexes exceeding the activity of cisplatin in the MDA-MB-231 cell line. All compounds showed moderate to good penetration into spheroids of DLD-1 cells with the distributions being consistent with active uptake of the pyrrole containing complexes in regions of the spheroids starved of nutrients.

Rational Development of Guanidinate and Amidinate Based Cerium and Ytterbium Complexes as Atomic Layer Deposition Precursors: Synthesis, Modeling, and Application.

Owing to the limited availability of suitable precursors for vapor phase deposition of rare‐earth containing thin‐film materials, new or improved precursors are sought after. In this study, we explored new precursors for atomic layer deposition (ALD) of cerium (Ce) and ytterbium (Yb) containing thin films. A series of homoleptic tris‐guanidinate and tris‐amidinate complexes of cerium (Ce) and ytterbium (Yb) were synthesized and thoroughly characterized. The C‐substituents on the N‐C‐N backbone (Me, NMe2, NEt2, where Me=methyl, Et=ethyl) and the N‐substituents from symmetrical iso‐propyl (iPr) to asymmetrical tertiary‐butyl (tBu) and Et were systematically varied to study the influence of the substituents on the physicochemical properties of the resulting compounds. Single crystal structures of [Ce(dpdmg)3] 1 and [Yb(dpdmg)3] 6 (dpdmg=N,N'‐diisopropyl‐2‐dimethylamido‐guanidinate) highlight a monomeric nature in the solid‐state with a distorted trigonal prismatic geometry. The thermogravimetric analysis shows that the complexes are volatile and emphasize that increasing asymmetry in the complexes lowers their melting points while reducing their thermal stability. Density functional theory (DFT) was used to study the reactivity of amidinates and guanidinates of Ce and Yb complexes towards oxygen (O2) and water (H2O). Signified by the DFT calculations, the guanidinates show an increased reactivity toward water compared to the amidinate complexes. Furthermore, the Ce complexes are more reactive compared to the Yb complexes, indicating even a reactivity towards oxygen potentially exploitable for ALD purposes. As a representative precursor, the highly reactive [Ce(dpdmg)3] 1 was used for proof‐of‐principle ALD depositions of CeO2 thin films using water as co‐reactant. The self‐limited ALD growth process could be confirmed at 160 °C with polycrystalline cubic CeO2 films formed on Si(100) substrates. This study confirms that moving towards nitrogen‐coordinated rare‐earth complexes bearing the guanidinate and amidinate ligands can indeed be very appealing in terms of new precursors for ALD of rare earth based materials.

Amidine/Amidinate Cobalt Complexes: One-Pot Synthesis, Mechanism, and Photocatalytic Application for Hydrogen Production.

A new synthetic route was carried out via a one-pot reaction to prepare a novel series of amidine/amidinate cobalt complexes 8-10 by mixing ligand 2 (6-pyridin-2-yl-[1,3,5]-triazine-2,4-diamine) with Co(II) in acetonitrile or benzonitrile. We observed that a change of solvent from methanol (used in complex 7, previously reported) to nitrile solvents (MeCN and PhCN) led to the in situ incorporation of the amidine group, ultimately forming 8-10. So far, this is a unique method reported to introduce amidine/amidinate groups into a pyridinyl-substituted diaminotriazine complex. Remarkably, the single crystal X-ray diffraction study (SCXRD) of these new compounds reveals associations involving Janus DATamidine and Janus DATamidinate. A mechanism is proposed to explain the formation of amidine/amidinate groups by investigating the single crystal structures of the possible intermediates 11 and 12 where the cobalt ion acts as a template. These amidine/amidinate cobalt complexes were used as a model to assess the photocatalytic activity for the hydrogen evolution reaction (HER). Complexes 9 and 10 show a 74% and 86% enhancement, respectively, of the catalytic activity towards the HER compared to complex 7. This highlights the structure-property relationship. By examining the novel cobalt complexes described here, we discovered the following: (i) a method to introduce an amidine group into a pyridine DAT-based complex, (ii) the efficiency of amidine complexes to form multiple hydrogen bonds to direct the molecular organization, (iii) the plausible mechanism of formation of amidines based on the SCXRD study, (iv) the modification of the final structure and hence the final properties by varying the reaction conditions, and (v) the utility of amidine complexes towards photocatalytic HER activity.

Computational Study of spx (x=1-3)-Hybridized Be-Be Bonds Stabilized by Amidinate Ligands.

Complexes containing odd-electron Be-Be bonds are still rare until now. Hereby, a series of neutral di-beryllium amidinate complexes containing a Be-Be bond were explored theoretically. The complexes with direct chelation with the Be2 dimer by the bidentate amidinate (AMD) ligands are always corresponding to their global minimum structures. The detailed bonding analyses reveal that the localized electrons of the Be-Be fragment can be adjusted by the amount of AMD ligands because each AMD ligand only takes one electron from the Be2 fragment. Meanwhile, the hybridization of the central Be atom also changes as the number of AMD ligands increases. In particular, the sp3 -hybridized single-electron Be-Be bond is firstly identified in the tri-AMD-ligands-chelated neutral D3h -Be2 (AMD)3 complex, which also possesses the higher stability compared to its monoanionic D3h -Be2 (AMD)3 - and monocationic C3 -Be2 (AMD)3 + analogues. Importantly, our study provides a new approach to obtain a neutral odd-electron Be-Be bond, namely by the use of radical ligands through side-on chelation.

Ligand Effects in Calcium Catalyzed Ketone Hydroboration

The first “naked” (Lewis base‐free) cationic Ca amidinate complex [tBuAmDIPPCa(C6H6)]+[B(C6F5)4]– was prepared in 62 % yield {tBuAmDIPP = tBuC(N–DIPP)2; DIPP = 2,6‐diisopropylphenyl} by reaction of [tBuAmDIPPCaH]2 with [Ph3C]+[B(C6F5)4]– in chlorobenzene. The ether‐free complex tBuAmDIPPCaN(SiMe3)2 was obtained by removal of diethyl ether from its ether adduct. Crystal structures show that the amidinate ligand in both complexes is N,Aryl‐chelating. In this coordination mode the bulk of the amidinate ligand is comparable to that of a DIPP‐substituted β‐diketiminate ligand. Isomers with N,N‐coordinating amidinate ligands are circa 15 kcal/mol higher in energy and this coordination mode is only present in case additional ether ligands compensate for energy loss or in case of space limitation at the metal, e.g. in homoleptic (tBuAmDIPP)2Ca. A series of four Ca amidinate complexes, tBuAmDIPPCaX, were tested in the catalytic hydroboration of ketones and aldehydes by pinacolborane (HBpin). Catalytic activities increase for X– = I– < B(C6F5)4– < (Me3Si)2N– ≈ H–. For catalysts with unreactive anions, like I– or B(C6F5)4–, catalyst performance increases with the Lewis acidity of the metal and a mechanism is proposed in which HBpin and ketone coordinate to the Ca2+ ion which is followed by direct hydroboration. The more active catalysts with X– = (Me3Si)2N– or H– likely operate through a mechanism which involves intermediate metal hydride (or borate) complexes.

Topological Analysis of Ag-Ag and Ag-N Interactions in Silver Amidinate Precursor Complexes of Silver Nanoparticles.

A series of silver amidinate complexes has been studied both experimentally and theoretically, in order to investigate the role of the precursor complex in the control of the synthesis of silver nanoparticles via an organometallic route. The replacement of the methyl substituent of the central carbon atom of the amidinate anion by a n-butyl group allows for the crystallization of the tetranuclear silver amidinate complex 3 instead of a mixture of di- and trinuclear silver amidinate complexes 1 and 2, as obtained with a methyl substituent. The relative stabilities and dissociation schemes of various isomeric arrangements of silver atoms in 3 are investigated at the computational DFT level of calculation, depending on the substituents of the amidinate ligand. The tetranuclear silver amidinate complex 4, exhibiting a diamondlike arrangement of the four silver atoms, is also considered. Ag-N bonds and argentophilic Ag-Ag interactions are finely characterized using ELF and QTAIM topological analyses and compared over the series of the related di-, tri-, and tetranuclear silver amidinate complexes 1-4. In contrast to the Ag-N dative bonds very similar over the series, argentophilic Ag-Ag interactions of various strengths and covalence degree are characterized for complexes 1-4. This gives insight into the role of the amidinate substituents on the nuclearity and intramolecular chemical bonding of the silver amidinate precursors, required for the synthesis of dedicated AgNPs with chemically well defined surfaces.

Lanthanocene and Cerocene Alkyl Complexes: Synthesis, Structure, and Reactivity Studies.

Lanthanocene and cerocene alkyl complexes [η5-1,3-(Me3C)2C5H3]2Ln(CH2C6H4-o-NMe2) (Ln = La 3 and Ce 4) were obtained from the salt metathesis of {[η5-1,3-(Me3C)2C5H3]2Ln(μ3-κ3-O3SCF3)2K(THF)2}2·THF (Ln = La 1·THF and Ce 2·THF) with LiCH2C6H4-o-NMe2. Reactivity of 3 and 4 toward various small molecules provides access to a series of lanthanide derivatives. For example, reactions of 3 and 4 with elemental chalcogens (sulfur and selenium) in 1:1 molar ratio give the lanthanide thiolates {[η5-1,3-(Me3C)2C5H3]2Ln(μ-SCH2C6H4-o-NMe2)}2 (Ln = La 5 and Ce 6) and selenolates {[η5-1,3-(Me3C)2C5H3]2Ln(μ-SeCH2C6H4-o-NMe2)}2 (Ln = La 7 and Ce 8). The compounds 3 and 4 react with two equivalents of elemental chalcogens (sulfur and selenium) to afford the lanthanide disulfides {[η5-1,3-(Me3C)2C5H3]2Ln}2(μ-η2:η2-S2) (Ln = La 9 and Ce 10) and diselenides {[η5-1,3-(Me3C)2C5H3]2Ln}2(μ-η2:η2-Se2) (Ln = La 11 and Ce 12). The lanthanide disulfides (9 and 10) or diselenides (11 and 12) can also be readily obtained through oxidation of the corresponding lanthanide thiolates (5 and 6) or selenolates (7 and 8) by elemental chalcogens concomitant with the (Me2N-o-C6H4CH2)2E2 (E = S or Se) release. Treatment of 3 and 4 with one equivalent or two equivalents of benzonitrile produces the serendipitous lanthanum and cerium-1-azaallyl complexes [η5-1,3-(Me3C)2C5H3]2Ln[N(H)C(Ph)═CHC6H4-o-NMe2] (Ln = La 13 and Ce 14) or amidine complexes [η5-1,3-(Me3C)2C5H3]2Ln[N(H)C(Ph)NC(Ph)═CHC6H4-o-NMe2]·C7H8 (Ln = La 15·C7H8 and Ce 16·C7H8), respectively. The compound 15 or 16 can also be readily synthesized by further insertion of one benzonitrile molecule into the 1-azaallyl complex 13 or 14. Insertion of N,N'-dicyclohexylcarbodiimide or phenyl isothiocyanate into Ln-C bonds within 3 and 4 results in the formation of the amidine complexes [η5-1,3-(Me3C)2C5H3]2Ln[CyNC(CH2C6H4-o-NMe2)NCy] (Cy = cyclohexyl, Ln = La 17 and Ce 18) or thioamidato complexes [η5-1,3-(Me3C)2C5H3]2Ln[SC(CH2C6H4-o-NMe2)NPh] (Ln = La 19 and Ce 20). All of the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.

Coordinative versatility in main group complexes of C-2,6-terphenyl substituted amidinates

The synthesis and characterization of two C-2,6-terphenyl substituted amidines, N,N′-dicyclohexyl-2,6-di(4-tolyl)benzamidine and N,N′-dicyclohexyl-2,6-dimesitylbenzamidine, are described. Both crystallize as the E-syn isomer, though interconversion between the E-syn and Z-syn isomers is observed for both in solution. These amidines are readily deprotonated by either n-butyllithium in THF or AlMe3 in toluene, affording the THF solvated lithium and dimethylaluminium amidinate complexes respectively. These complexes have been characterized in the solid-state using single-crystal X-ray crystallography. The identity of the 2,6-substituents on the secondary arene rings of the terphenyl group plays a significant role in the coordination motif adopted by the amidinate, as well as the potential to access bis(amidinato)metal complexes.

The amidine formed by tacrine and saccharin revisited: An ab initio Investigation of Structural, Electronic and Spectroscopic Properties

Computational study of tacrine and saccharin and their amidine complex (TacSac) was peformed by ab initio calculations including electron correlation. Structure, UV-Vis spectra and charge distribution of the amidine (TacSac) were investigated using ground state geometries optimized at MP2/6-311++G(d,p) level. The effects of solvent was investigated using polarizable continuum model (PCM) in conjunction with the solvation model based on density (SMD) approach. TacSac geometry remained same in gas phase and in H2O both with PCM and SMD models in contrast to former DFT results. The amidine is calculated to be stable indicating that former DFT calculations underestimated the stability of the investigated amidine. UV-Vis spectra and electronic transitions were calculated at CIS/6-311++G(d,p), B3LYP/6-311++G(d,p) and CAM-B3LYP/6-311++G(d,p) levels of theory and B3LYP gave the best results. TacSac has a peak at a higher wavelength enabling S0→S1 transition with a lower energy. S0→S1 transition corresponds to full charge transfer between HOMO and LUMO orbitals of TacSac in H2O. The ab initio results indicate that the TacSac system can be synthesized with an easy condensation reaction, and that the amidine product is a potential candidate for photochemical charge-transfer systems.

Ruthenium Aqua Complexes Supported by the Kläui Tripodal Ligand: Synthesis, Structure, and Application in Catalytic C–H Oxidation in Water

Water‐soluble ruthenium(III) aqua complexes supported by the Kläui tripodal ligand [Co(η5‐C5H5){P(O)(OEt)2}3]– (LOEt–) have been synthesized and structurally characterized, and their use as catalysts for C–H oxidation in water has been studied. The treatment of [Ru(LOEt)Cl2(MeCN)] with N‐donor ligands afforded the adducts [Ru(LOEt)Cl2(L)] (L = tBuNH2 (1), pyridine (2), imidazole (3)). Refluxing [Ru(LOEt)Cl2(MeCN)] in neat tBuNH2 gave the amidine complex [Ru(LOEt)Cl2{N(H)C(Me)NHtBu}] (4). Chloride abstraction of 1–3 with AgOTs (OTs = tosylate) in 1 M p‐toluenesulfonic acid afforded the water‐soluble RuIII diaqua complexes [Ru(LOEt)(H2O)2(L)](OTs)2 (L= tBuNH2 (5), pyridine (6), imidazole (7)), whereas that for 4 yielded the triaqua complex [Ru(LOEt)(H2O)3](OTs)2 (8). The crystal structures of 4, 5, 7, and 8 have been determined. The reduction of 5 with Zn dust in D2O gave a diamagnetic RuII species, whereas that in MeCN led to isolation of the RuII acetonitrile complex [RuII(LOEt)(MeCN)2(tBuNH2)](PF6) (9), which has been characterized by X‐ray diffraction. The RuIII aqua complexes proved to be moderately efficient catalysts for C–H bond oxidation with tert‐butyl hydroperoxide in water. For example, the oxidation of ethylbenzene with tert‐butyl hydroperoxide in water at room temperature in the presence of 0.1 mol‐% of 8 afforded acetophenone in ca. 62 % yield.