Superior electrocatalytic hydrogen evolution activity of a triply bridged diruthenium(II) complex on a carbon cloth support.

This article describes the structural authentication of a unique triply bridged [1](ClO4)2 and monomeric [2]ClO4/[3]ClO4. Electrochemical HER on a carbon cloth support demonstrated the superior performance of [1](ClO4)2 with high TON (>105) and its long-term stability. The primary kinetic isotope effect of [1](ClO4)2 revealed the involvement of PCET in the rate-determining step.

Sequential Oxygenation of Bis(ß-diketiminate) on a Selective Diruthenium Platform.

This article demonstrated the redox-noninnocent phenylene-linked bis(ß-diketiminate) (L2-)-bridged first example of isomeric diruthenium(III)-acac species (acac = acetylacetonate) and its ability to activate dioxygen. The coordination of deprotonated L2- to the {Ru(acac)2} in bis(bidentate) mode led to isomeric {(acac)2RuIII}2(µ-L2-) (S = 1, 1-trans/1-cis, green). 1 displayed Ru(III)-based anisotropic EPR in CH3CN but without the resolution of the forbidden (ΔMs = 2) g1/2 signal at 77 K. 1-cis, however, slowly transformed to the energetically favored 1-trans form. 1 underwent two-step oxygenation at the Cß sites of L2- to form the ß-diketiminate/α-ketodiimine (L'-)-bridged mixed valent (acac)2RuIII(µ-L'-)RuII(acac)2 (2, S = 1/2, pink) followed by bis(α-ketodiimine) (L″)-bridged isovalent (acac)2RuII(µ-L″)RuII(acac)2 (3, S = 0, red). The role of O2 toward 1 → 2/3 was corroborated by 18O2 labeling experiment. Redox steps of 1-3 varied as a function of isomeric identity, bridge, and metal oxidation state. The calculated MOs and Mulliken spin densities attributed to the noninnocence of L2-, L'-, and L″ in the respective complexes. Spectrophotometric monitoring of 1 → 2 revealed pseudo-first-order rate constants (105k s-1) of 1.8 (303 K), 3.5 (313 K), 7.7 (323 K), and 17.0 (333 K) and ΔH⧧/ΔS⧧/ΔG⧧ of 14.3 kcal mol-1/-33.1 cal mol-1 K-1/24.2 kcal mol-1 (298 K), respectively. Moreover, characterization of the short-lived blue intermediate obtained during the conversion of 1 → 2/3 upon exposure to O2 supported its valence tautomeric form (VT1, RuIII-L2--RuIII ↔ RuIII-L•--RuII, S = 1), which in effect facilitated oxygen activation at the ligand backbone.

Tetracoordinated 15-Electron Ruthenium(I) in a Discrete Triruthenium Framework.

This paper highlights the unique case of a tetracoordinated Ru(I) (15-electron) component in a structurally characterized discrete triruthenium setup, [(acac)2RuIIIL1(µ-RuI)L1RuII (acac)2](ClO4)2 ([3](ClO4)2, where acac = acetylacetonate; S = 1), which was formed along with the monomeric [(acac)2RuIII(L1)] ([1]ClO4; S = 1/2) and dimeric [{(acac)2RuIII}2(µ-L1)](ClO4)2 ([2](ClO4)2; S = 1) counterparts upon interaction of {Ru(acac)2} and L1 = 3,3'-dipyridin-2-yl-1,1'-bis(imidazo[1,5-a]pyridinyl).

Unique Metal-Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C-C Coupling, and Receptor Feature.

This article dealt with the ruthenium and osmium derivatives of isomeric 1H-indazole-3-carboxylic acid/2H-indazole-3-carboxylic acid (H2L1) and 1H-benzimidazole-2-carboxylic acid (H2L2) along with the π-acidic bpy (bpy = 2,2'-bipyridine) and pap (pap = 2-phenylazopyridine) co-ligands. It thus extended structurally authenticated monomeric ([(bpy)2RuII(HL1-)]ClO4 [1]ClO4, (pap)2RuII(L12-) 2, (bpy)2OsII(L12-) 3, (pap)2OsII(L12-) 4, (bpy)2RuII(L22-) 5, (bpy)2OsII(L22-) 8, and (pap)2OsII(L22-) 9) and dimeric ([(bpy)2RuII(µ-L22-)RuII(bpy)2](ClO4)2 [6](ClO4)2) complexes. It also described modified L2'2- (L2'2- = 2,2'-bisbenzimidazolate)-bridged [(pap)2RuII(µ-L2'2-)RuII(pap)2](ClO4)2 [7](ClO4)2, where L2'2- was developed selectively with the {Ru(pap)2} metal fragment via in situ intermolecular C-C coupling of the two units of decarboxylated benzimidazolate. Moreover, chemical oxidation (OsII to OsIII) of (bpy)2OsII(L12-) 3 (E0 = 0.11 V versus SCE) and (bpy)2OsII(L22-) 8 (E0 = 0.12 V versus SCE) by AgClO4 yielded unprecedented OsIII-AgI derived polymeric {[(bpy)2OsIII-L12--AgI(CH3CN)](ClO4)2}n {[10](ClO4)2}n and dimeric [(bpy)2OsIII-L22--AgI(CH3CN)](ClO4)2 [11](ClO4)2 complexes as a function of trans and cis orientations of the active N2 donor with special reference to the carboxylate O2 of L2-, respectively. Microscopic (FE-SEM, TEM-EDX, and AFM) and DLS experiments suggested a homogeneously dispersed hollow spherical shaped morphology of {[10](ClO4)2}n with an average particle size of 200-400 nm as well as its non-dissociative feature in the aprotic medium. Experimental (structure, spectroscopy, and electrochemistry) and theoretical (DFT/TD-DFT) explorations revealed a redox non-innocent feature of L2- in the present coordination situations and the selective anion sensing (X = F-, CN-, and OAc-) event of [1]ClO4 involving a free NH group at the backface of HL1-, which proceeded via the NH···X hydrogen bonding interaction.

Indazole-Derived Mono-/Diruthenium and Heterotrinuclear Complexes: Switchable Binding Mode, Electronic Form, and Anion Sensing Events.

The article deals with the newer classes of mononuclear: [(acac)2RuIII(H-Iz)(Iz-)] 1, [(acac)2RuIII(H-Iz)2]ClO4 [1]ClO4/[1']ClO4, and [(bpy)2RuII(H-Iz)(Iz-)]ClO4 [2]ClO4, mixed-valent unsymmetric dinuclear: [(acac)2RuIII(µ-Iz-)2RuII(bpy)2]ClO4 [3]ClO4, and heterotrinuclear: [(acac)2RuIII(µ-Iz-)2MII(µ-Iz-)2RuIII(acac)2] (M = Co:4a, Ni:4b, Cu:4c, and Zn:4d) complexes (H-Iz = indazole, Iz- = indazolate, acac = acetylacetonate, and bpy = 2,2'-bipyridine). Structural characterization of all the aforestated complexes established their molecular identities including varying binding modes (Na and Nb donors and 1H-indazole versus 2H-indazole) of the heterocyclic H-Iz/Iz- in the complexes. Unlike [1']ClO4 containing two NH protons at the backface of H-Iz units, the corresponding [1]ClO4 was found to be unstable due to the deprotonation of its positively charged quaternary nitrogen center, and this resulted in the eventual formation of the parent complex 1. A combination of experimental and density functional theory calculations indicated the redox noninnocent feature of Iz- in the complexes along the redox chain. The absence of intervalence charge transfer transition in the near-infrared region of the (Iz-)2-bridged unsymmetric mixed-valent RuIIIRuII state in [3]ClO4 suggested negligible intramolecular electronic coupling corresponding to a class I setup (Robin and Day classification). Heterotrinuclear complexes (4a-4d) exhibited varying spin configurations due to spin-spin interactions between the terminal Ru(III) ions and the central M(II) ion. Though both [3]ClO4 and 4a-4d displayed ligand (Iz-/Iz•)-based oxidation, reductions were preferentially taken place at the bpy and metal (RuIII/RuII) centers, respectively. Unlike 1 or [2]ClO4 containing one free NH proton at the backface of H-Iz, [1']ClO4 with two H-Iz units could selectively and effectively recognize F-, OAc-, and CN- among the tested anions: F-, OAc-, CN-, Cl-, Br-, I-, SCN-, HSO4-, and Η2PΟ4- in CH3CN via intermolecular NH···anion hydrogen bonding interaction. The difference in the sensing feature between [1']ClO4 and 1/[2]ClO4 could be rationalized by their pKa values of 8.4 and 11.3/10.8, respectively.

Bidirectional noninnocence of hinge-like deprotonated bis-lawsone on selective ruthenium platform: a function of varying ancillary ligands.

The present work aimed to obtain discrete heavier metal complexes of unperturbed deprotonated bis-lawsone (hinge-like H2L = 2,2'-bis(3-hydroxy-1,4-napthoquinone). This is primarily due to its limited examples with lighter metal ions (Co, Zn, and Ga) and the fact that our earlier approach with the osmium ion facilitated its functionalisation. Herein, we demonstrated the successful synthesis and structural characterisation of L2--derived diruthenium [(bpy)2RuII(µ-L2-)RuII(bpy)2](ClO4)2 [1](ClO4)2 (S = 0), (acac)2RuIII(µ-L2-)RuIII(acac)22 (S = 1) and monoruthenium (pap)2Ru(L2-) 3 (S = 0) derivatives (bpy = 2,2'-bipyridine, acac = acetylacetonate, and pap = 2-phenylazopyridine). The crystal structures established that (i) O,O-/O,O- donating five-membered bis-bidentate and O-,O- donating seven-membered bidentate chelating modes of deprotonated L2- in rac (ΔΔ/ΛΛ) diastereomeric [1](ClO4)2, 2 and 3, respectively. (ii) The L2- bridging unit in [1](ClO4)2, 2 and 3 underwent twisting its two naphthoquinone rings with respect to the ring connecting C-C bond by 73.01°, 62.15° and 59.12°, respectively. (iii) Intermolecular π-π interactions (∼3.5 Å) between the neighbouring molecules. The paramagnetic complex 2 (S = 1) with two non-interacting Ru(III) (S = 1/2) ions exhibited weak antiferromagnetic coupling only at very low temperatures. In agreement with the magnetic results, 2 displayed typical RuIII-based anisotropic EPR in CH3CN (/Δg: 2.314/0.564) but without any forbidden g1/2 signal at 120 K. The complexes exhibited multiple redox processes in CH3CN in the experimental potential window of ± 2.0 V versus SCE. The analysis of the redox steps via a combined experimental and theoretical (DFT/TD-DFT) approach revealed the involvement of L2- to varying extents in both the oxidative and reductive processes as a consequence of its bidirectional redox non-innocent feature. The mixing of the frontier orbitals of the metal ion and L2- due to their closeness in energy indeed led to the resonating electronic form in certain redox states instead of any precise electronic structural state.

Structural and electronic forms of doubly oxido/Pz and triply oxido/(Pz)2 bridged mixed valent and isovalent diruthenium complexes (Pz = pyrazolate).

The article reported on the diastereomeric dinuclear mixed-valent complexes [(acac)2Ru(III)(µ-O)(µ-PzR)Ru(IV)(acac)2] (R = H, Me, meso: ΔΛ, 1a-1c; rac: ΔΔ/ΛΛ, 2a-2c) and rac-[(acac)2Ru(III)(µ-O)(µ-Iz)Ru(IV)(acac)2], (2d) (HPz = pyrazole, HIz = indazole, acac = acetylacetonate). Moreover, the diruthenium(II,II) complexes [(HPz)3Ru(II)(µ-O)(µ-Pz)2 Ru(II)(HPz)3] (3a) and [(HIz)3Ru(II)(µ-O)(µ-Iz)2Ru(II)(HIz)3] (3d) were presented. The analogous form of 3a, i.e., [(HPz)2(Pz)Ru(III)(µ-O)(µ-Pz)2Ru(III)(Pz)(HPz)2], was previously reported. Single crystal X-ray structures of 1a-1c/2a-2d and representative 3a showed their molecular forms, including the diastereomeric nature of the former. The Ru-O-Ru angle decreased appreciably on switching from doubly bridged 1 and 2 (128-135°) to triply bridged 3a (114°). Both series of complexes displayed rhombic symmetry in their EPR spectra, with g1 and g2 being very similar for 1a-1c with an almost axial look. The mixed-valence complex with a Ru(III)Ru(IV) (S = 1/2) state of 1 and 2 would lead to iso-valence complexes of Ru(III)Ru(III) and Ru(IV)Ru(IV) with an EPR inactive state by one electron redox reaction. On the other hand, metal based {Ru(II)Ru(II)/Ru(II)Ru(III), 3a/3a+} and terminal ligand (HPz/HPz-, 3a/3a-) based redox processes displayed anisotropic and free radical EPR, respectively. An IVCT (intervalence charge transfer) band was found for the delocalised mixed valent 1 and 2 {Ru(III)Ru(IV)} or 3a+ {Ru(II)Ru(III)} in the NIR region. The intense metal-to-ligand charge transfer (MLCT) transitions of 1-3 in the visible region varied systematically as a function of the metal oxidation state.

Noninnocence of the deprotonated 1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine bridge in diruthenium frameworks - a function of co-ligands.

The article deals with the sensitive electronic forms in accessible redox states of structurally and spectroscopically authenticated deprotonated 1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (H2LR, R = H) or 1,2-bis((3,5-dimethyl-1H-pyrrol-2-yl)methylene)hydrazine (H2LR, R = Me), a BODIPY analogue bridged diruthenium complex as a function of varying ancillary ligands. It involved rac-(acac)2RuIII(µ-LR 2-)RuIII(acac)21a, R = H; 1b, R = Me (S = 1, acac = acetylacetonate), rac-[(bpy)2RuII(µ-L2-)RuII(bpy)2](ClO4)2 [2](ClO4)2 (S = 0, bpy = 2,2'-bipyridine) and diastereomeric [(pap)2RuII(µ-L2-)RuII(pap)2](ClO4)2meso-[3a](ClO4)2/rac-[3b](ClO4)2 (S = 0, pap = phenylazopyridine). The crystal structure established the linkage of the conjugated -C5[double bond, length as m-dash]N2-N3[double bond, length as m-dash]C6- central unit with the two terminal deprotonated pyrrole units of coordinated L2-. The bridging L2- in 1a, 1b, [2](ClO4)2, [3b](ClO4)2 and [3a](ClO4)2 was slightly twisted and planar with torsional angles of 41.54°, 42.91°, 37.38°, 35.33° and 0°, respectively, with regard to the central N2-N3 bond. The extent of twisting of the bridge followed an inverse relationship with the RuRu separation: 4.935/4.934 Å 1a/1b < 5.141 Å [2](ClO4)2 < 5.201 Å [3b](ClO4)2 < 5.351 Å [3a](ClO4)2. This is also attributed to the intermolecular ππ/CHπ interactions between the nearby aromatic rings of L and bpy or pap in [2](ClO4)2 or [3](ClO4)2, respectively. The multiple redox steps of the complexes varied appreciably based on the σ-donating (acac) and π-acidic (bpy, pap) characteristics of the ancillary ligands. Experimental (structure, EPR) and theoretical (DFT) evaluation pertaining to the electronic forms of 1n, 2n and 3n demonstrated the preferential involvement of L based frontier orbitals in electron transfer processes even in combination with the redox facile ruthenium ion. This in turn highlighted its redox non-innocent feature as in the case of well-documented metal coordinated quinonoid, formazanate, diimine (bpy), azo (pap) and ß-diketiminate functions.

Osmium(II)-Coordination Induced C-C Bond Functionalization of Bis-lawsone.

Metal-coordination-driven C-C bond functionalization without involvement of the traditional route of oxidative addition, insertion, and reductive elimination has gained immense importance. In this context, the present Communication highlights the facile ring contraction process of the deprotonated bis-lawsone (L2-) to functionalized L12- upon coordination to {Os(bpy)2} or isomeric {Os(pap)2} (bpy = 2,2'-bipyridine and pap = 2-phenylazopyridine) in 1-3. Further, recognition of fractional redox noninnocence of L1 in 1+-3+ via experimental and theoretical events facilitated its inclusion in the redox noninnocent family.

The Indigo Isomer Epindolidione as a Redox-Active Bridging Ligand for Diruthenium Complexes.

Epindolidione (H2 L), a heteroatom-modified analogue of tetracene and a structural isomer of indigo, forms dinuclear complexes with [RuX2 ]2+ , X=bpy (2,2'-bipyridine, [1]2+ ) or pap (2-phenylazopyridine, [2]2+ ), in its doubly deprotonated bridging form µ-L2- . The dications in compounds meso-[1](ClO4 )2 and meso-[2](ClO4 )2 , [X2 Ru(µ-L)RuX2 ](ClO4 )2 , contain five-membered chelate rings N-C-C-O-RuII with π bridged metals at an intramolecular distance of 7.19 Å. Stepwise reversible oxidation and reduction is mainly ligand centered (oxidation: L2- ; reduction: X), as deduced from EPR of one-electron oxidized and reduced intermediates and from UV/Vis/NIR spectroelectrochemistry, supported by TD-DFT calculation results. The results for [1](ClO4 )2 and [2](ClO4 )2 are qualitatively similar to the ones observed with the deprotonated indigo-bridged isomers with their six-membered chelate ring structures, confirming the suitability of both π systems for molecular electronics applications, low-energy absorptions, and multiple electron transfers.

Unprecedented metal-metal bonded {Ru4(µ3-O)2} butterfly core in oxido-carboxylato bridged mixed valence cluster-structural elucidation and electronic forms in accessible redox states.

Unprecedented metal-metal bonded oxido-carboxylato bridged mixed valence tetraruthenium cluster [(acac)6Ru(µ3-O)2(µ-CH3COO)3] 1 (S = 1/2) (acac = acetylacetonate) with {Ru4(µ3-O)2} "butterfly" core has been achieved via the reaction of Ru(acac)2(CH3CN)2 with excess CH3COONa (Ru : CH3COONa = 1 : 15) in refluxing EtOH-H2O (5 : 1). Structural analysis of 1 ascertained a unique Ru-Ru bonded (Ru2-Ru3: 2.5187(6) Å (DFT: 2.560 Å)) {Ru2(Ru-Ru)(µ3-O)2} butterfly core, unlike the reported other Fe4 or Mn4 derived "butterfly" core. The connectivity of Ru4(µ3-O)2 core in 1 with three Ru2(µ-CH3COO)3 and two each Ru-(acac)2/Ru-acac units resulted in interconnected four RuO6 octahedral entities. The doubly bridged µ3-O2- ions of the nearly planar central metal-metal bonded Ru2O2 core (Ru2-Ru3, "body" or "hinge") linked to the remaining two "wing-tip" Ru atoms (Ru1 and Ru4). Complex 1 with a S = 1/2 spin state displayed paramagnetically shifted 1H NMR over a wide chemical shift range in CDCl3 (δ, 13 to -30 ppm) and a metal based anisotropic EPR (g1 = 2.17, g2 = 2.01, g3 = 1.86; Δg = g1-g3 = 0.31 and 〈g〉 = [1/3(g12 + g22 + g32]1/2 = 2.01) at 100 K in CH3CN-toluene. The metal based one-electron reversible oxidation at 0.49 V and reduction at 0.485 V versus SCE of 1 led to the EPR inactive (even at 4 K) spin-coupled RuIIIRuIIIRuIVRuIV (S = 0) and RuIIIRuIIIRuIIIRuIII (S = 0) electronic configurations for 1+ and 1-, respectively. Mixed valence 1 and 1+ exhibited low-energy near-infrared (NIR) absorption bands at 1350 nm and 1156 nm, respectively, in CH3CN. A combined experimental (UV-vis-NIR and EPR spectroelectrochemistry) and theoretical (DFT) analysis indicated a delocalised mixed valence form of 1 ({Ru2(Ru-Ru)(µ3-O)2}).

Three Bis-BODIPY Analogous Diruthenium Redox Series: Characterization and Electronic Structure Analysis.

The dianion derived from (2Z,6Z)-3,7-diphenyl-N2,N6-di(pyridin-2-yl)pyrrolo[2,3-f]indole-2,6(1H,5H)-diimine (H2 BL), a modified BODIPY ligand precursor, is shown to be capable of bridging two metal complex fragments RuL2 , L=2,4-pentanedionato (acac- ), 2,2'-bipyridine (bpy) or 2-phenylazopyridine (pap) in [Ru(acac)2 Ru(µ-BL)Ru(acac)2 ] (1/2), [Ru(bpy)2 Ru(µ-BL)Ru(bpy)2 ](ClO4 )2 ([3](ClO4 )2 ) and [Ru(pap)2 Ru(µ-BL)Ru(pap)2 ](ClO4 )2 ([4](ClO4 )2 ). The compounds, including a diastereoisomeric pair 1 (meso) and 2 (rac) were spectroscopically and structurally characterized. Reversible electron transfers as revealed by cyclic and differential pulse voltammetry allowed for an EPR and UV-vis-NIR spectroelectrochemical investigation of several neighboring charge states. Together with susceptibility measurements and TD-DFT calculations the assignment of oxidation states reveals that 1, 2 are diruthenium(III) species which can be oxidized or reduced by one electron whereas 32+ and 42+ contain ruthenium(II) and get reduced or oxidized mainly at the dianionic bridge (32+ ) or are reduced at the ancillary ligands pap (42+ ).

Mixed-Valent RuIIIRuIV Configuration in an Oxido-Carboxylato-Bridged Diastereomeric Pair.

An unprecedented diastereomeric pair [meso, ΔΛ (1); rac, ΔΔ/ΛΛ (2)] involving a doubly oxido-carboxylato-bridged mixed-valent RuIIIRuIV (d5d4, S = 1/2) state in [(acac)2RuIII(µ-O)(µ-CH3COO)RuIV(acac)2] (acac = acetylacetonate) was structurally characterized. 1n and 2n (n = +, 0, -) display comparable spectroelectrochemical features for the accessible redox states.

Ruthenium-Chelated Non-Innocent Bis(heterocyclo)methanides: A Mimicked ß-Diketiminate.

The unexplored substrate-based reactivity profile of newly designed bis(heterocyclo)methanide (BHM, L1-L3), a structural mimic of ubiquitous ß-diketiminate, was demonstrated on an electronically rich {Ru(acac)2} platform (acac = σ-donating acetylacetonate). In this regard, this work deals with structurally characterized [Ru(L)(acac)2] complexes 1A-3A incorporating electronically varying heterocycles {1A, L1 = bis(imidazo[1,5-a]pyridin-3-yl)methanide; 2A, L2 = (Z)-4-[(6,7-dihydrothieno[3,2-c]pyridin-4-yl)methylene]-6,7-dihydro-4H-thieno[3,2-c]pyridin-5-ide; 3A, L3 = (Z)-6-chloro-1-[(6-chloro-3,4-dihydroisoquinolin-1-yl)methylene]-3,4-dihydro-1H-isoquinolin-2-ide}. The significant impact of electronic modification at the BHM backbone (L1-L3) on its redox tunability at the metal-ligand interface in 1A-3A and its subsequent oxygenation profile to yield bis(heterocyclo)methanone (BMO, analogue of α-ketodiimine) in the corresponding [Ru(BMO)(acac)2] (1B-3B) via a radical pathway were rationalized. In addition, oxidative dehydrogenation of metalated BMO in 1B-3B to BAM [bis(heteroaryl)methanone] in [Ru(BAM))(acac)2] (1C-3C) was illustrated in support of the nonspectator behavior of α-ketodiimine. A combined experimental and theoretical investigation extended mechanistic outlines of the aforementioned transformation processes, which in effect provided a new dimension relating to the analogous ß-diketiminate as well as α-ketodiimine chemistry.

Diverse modes of functionalisation of ruthenium coordinated ß-ketoiminate analogues.

This article compares the reactivity patterns of ß-ketoiminate (AcNac) and ß-thioacetyliminate (SacNac), with special reference to the unsymmetrical ß-diketiminate (NacNac), on the selective {Ru(acac)2} metal platform that encompasses the electronically rich acac (= acetylacetonate) moiety. In this regard, structural and spectroelectrochemical aspects have been reported for the newly designed complexes [RuIII(acac)2(AcNacR)] (1a-1c), [RuIII(acac)2(SacNacH)] (2) and [RuIII(acac)2(NacNacR)] (3a-3c) [R = para-substituents (H, Cl, OMe) of the N-bearing aryl group]. The subsequent exploration of the impact of metal chelation on the reactivity profile of the ß-ketoiminate analogues revealed the following: (a) the facile oxygenation of the methine centre (Cß-H) of the unsymmetrical NacNac in 3 led to ketodiimine (L1) in [RuII(acac)2(L1)] (4), while analogues AcNac and SacNac in 1 and 2, respectively, remained resistant to oxidative functionalisation due to their relatively lower charge densities at the methine (Cß) centres. (b) Hydrolysis of the relatively weak C-S bond of SacNac resulted in a µ3-S bridged [{Ru(acac)2}3(µ3-S)] complex (2'). (c) Unlike 2 and 3, AcNac in 1 underwent an interesting transformation selectively in a non-polar solvent (toluene) to the 3-acetyl AcNac (L2-) moiety in 5 ([RuIII(acac)2(L2)]) via the generation of a new C-C bond at its backbone, indicating the ambiphilic feature of AcNac. The paper also addresses the aforesaid transformation processes and fractional redox non-innocence of AcNac, SacNac and NacNac in 1n, 2n and 3n (n = +1, 0, -1), respectively.