Axial interaction of the [Ru<SUB>2</SUB>(CO)<SUB>4</SUB>]<SUP>2+</SUP> core with the Aryl C−H Bond: route to cyclometalated compounds involving a metal−metal-bonded diruthenium unit

Room-temperature activation of the aromatic C−H bond by the [Ru2(CO)4]2+ core has been achieved. The reactions of 2-phenyl-1,8-naphthyridine (phNP) and 2-(2,5-dimethyl-3-furyl)-1,8-naphthyridine (Me2fuNP) with [Ru2(CO)4(MeCN)6][BF4]2 in dichloromethane provide the agostic-cyclometalated compounds [Ru2(phNP)(C6H4-NP)(CO)4][BF4] (1) and [Ru2(Me2fuNP)(C4OMe2-NP)(CO)4][BF4] (2), respectively. In both compounds, one of the ligands is ortho-metalated, while the second ligand is engaged in an agostic interaction. The ortho metalation is preferred over the potential S coordination for 2-(2-thienyl)-1,8-naphthyridine (thNP), yielding [Ru2(thNP)(C4H2S-NP)(CO)4][BF4] (3). In acetonitrile, the compound [Ru2(thNP)2(CO)4][BF4]2 (4) is obtained exclusively. The donation of a C−H bonding electron pair to the Ru−Ru σ* LUMO and back-donation from the filled Ru−Ru π* orbital to the C−H σ* orbital cause facile C−H bond cleavage. In contrast, the isoelectronic [Rh2]4+ provides the agostic compounds [Rh2(OAc)3(phNP)C1] (5) and [Rh2(L)(η1-L)(OAc)2(CH3CN)2][BF4]2 (L = phNP, nplNP (2-(2-naphthyl)-1,8-naphthyridine) for compounds 6 and 7, respectively). The molecular structures of compounds 1−3, 5, and 7 have been established by X-ray crystallography

C−C bond forming reaction through aldol-type addition mediated by a [Ru<SUB>2</SUB>(CO)<SUB>4</SUB>]<SUP>2+</SUP> core

An aldol-like addition of acetone to 2-methyl-1,8-naphthyridine and 2,3-dimethyl-1,8-naphthyridine mediated by a [Ru<SUB>2</SUB>(CO)<SUB>4</SUB>]<SUP>2+</SUP> core at room temperature affords the C−C-coupled compounds 2-methyl-1-(1,8-naphthyridin-2-yl)propan-2-ol (L1) and 2-methyl-1-(3-methyl-1,8-naphthyridin-2-yl)propan-2-ol (L2). A similar reaction with methyl ethyl ketone and 2-methyl-1,8-naphthyridine affords 2-methyl-1-(1,8-naphthyridin-2-yl)butan-2-ol (L3). The syntheses and structures of [Ru<SUB>2</SUB>(CO)<SUB>4</SUB>(L1)<SUB>2</SUB>][X]<SUB>2</SUB> (2, X = BF<SUB>4</SUB>; 2a, X = OTf), [Ru<SUB>2</SUB>(CO)<SUB>4</SUB>(L2)<SUB>2</SUB>][BF<SUB>4</SUB>]<SUB>2</SUB> (3), and [Ru<SUB>2</SUB>(CO)<SUB>4</SUB>(L3)<SUB>2</SUB>][BF<SUB>4</SUB>]<SUB>2</SUB> (4) are reported here

Ligand assisted homolytic cleavage of the Ru–Ru single bond in [Ru<SUB>2</SUB>(CO)<SUB>4</SUB>]<SUP>2+</SUP> core and the chemical consequence

The Ru–Ru single bond in [Ru2(CO)4(MeCN)6][BF4]2 remains intact in the reaction with 2-i-propyl-1,8-naphthyridine (iPrNP) and the isolated product is the cis-[Ru2(iPrNP)2(CO)4(OTf)2] (1) obtained via crystallization in the presence of [n-Bu4N][OTf]. The 2-t-butyl-1,8-naphthyridine (tBuNP), on the contrary, leads to the oxidative cleavage of the Ru–Ru single bond resulting in the trans-[Ru(tBuNP)2(MeCN)2][BF4]2[NC(Me)C(Me)N] (2). The anti-[NC(Me)C(Me)N]2- is the product of the two-electron reductive coupling of two acetonitrile molecules. The phenoxo appendage in 2-(2-hydroxyphenyl)-1,8-naphthyridine (hpNP) brings the identical effect of the scission of the Ru–Ru bond but the process is non-oxidative and the product obtained is the cis-[Ru(hpNP)2(CO)2][BF4] (3). The bis-(diphenylphosphino)methane (dppm) in dichloromethane oxidatively cleave the Ru–Ru bond leading to chloro bridged [Ru(μ-Cl)(dppm)(CO)(MeCN)]2[BF4]2 (4). All the complexes have been characterized by the spectroscopic and electrochemical measurements and their structures have been established by X-ray diffraction study

Effects of axial coordination on the Ru−Ru single bond in diruthenium paddlewheel complexes

The 1,8-naphthyridine-based (NP-based) ligands with furyl, thiazolyl, pyridyl, and pyrrolyl attachments at the 2-position have been synthesized. Reactions of 3-MeNP (3-methyl-1,8-naphthyridine), fuNP (2-(2-furyl)-1,8-naphthyridine), tzNP (2-(2-thiazolyl)-1,8-naphthyridine), pyNP (2-(2-pyridyl)-1,8-naphthyridine), and prNP- (2-(2-pyrrolyl)-1,8-naphthyridine) with [Ru2(CO)4(CH3CN)6]2+ lead to [Ru2(3-MeNP)2(CO)4(OTf)2] (1), [Ru2(fuNP)2(CO)4]2[BF4]2 (2), [Ru2(tzNP)2(CO)4][ClO4]2 (3), [Ru2(pyNP)2(CO)4][OTf]2 (4), and [Ru2(prNP)2(CO)4] (5). The molecular structures of complexes 1−5 have been established by X-ray crystallographic studies. The modulation of the Ru−Ru single-bond distances with axial donors triflates, furyls, thiazolyls, pyridyls, and pyrrolyls has been examined. A small and gradual increase in the Ru−Ru distance is measured with various donors of increasing strengths. The shortest Ru−Ru distance of 2.6071(9) Å is observed for the axially coordinated triflates in complex 1, and the longest Ru−Ru distance of 2.6969(10) Å is measured for axial pyrrolyls in complex 5. The Ru−Ru distances in complexes 3 (2.6734(7) Å) and 4 (2.6792(9) Å), having thiazolyls and pyridyls at axial sites respectively, are similar. The Ru−Ru distance for axial furyls in complex 2 (2.6261(9) Å) is significantly shorter than the corresponding distances in 3, 4, and 5. DFT calculations provide insight into the interaction of the Ru−Ru σ orbital with axial donors. The Ru−Ru σ orbital is elevated to a higher energy because of the interaction with axial lone pairs. The degree of destabilization depends on the nature of axial ligands:  the stronger the ligand, higher the elevation of Ru−Ru σ orbital. The lengthening of Ru−Ru distances with respect to the axial donors in compounds 1−5 follows along the direction pyrrolyl > pyridyl ≈ thiazolyl > furyl > triflate, and the trend correlates well with the computed destabilization of the Ru−Ru σ orbitals

Oxidative route to polyoxomolybdates from quadruply bonded [Mo<SUP>II</SUP>≣Mo<SUP>II</SUP>] precursor: Structural characterization of a tetranuclear cluster [Mo<SUB>4</SUB>Cl<SUB>5</SUB>O<SUB>8</SUB>(pyNP)<SUB>2</SUB>] (pyNP=(2-(2-pyridyl)1,8-naphthyridine))

Aerial oxidation of the quadruply bonded Mo2(OAc)4 in the presence of HprNP (2-(2-pyrrolyl)-1,8-naphthyridine) in CH2Cl2 provide the dinuclear oxochloromolybdate [Mo2O2Cl2(μ2-O)2(HprNP)2] (1). The molecular structure of 1 consists of the [Mo2O2Cl2(μ2-O)2] core with the cisoid Mo=O bonds and each HprNP ligand chelating the Mo center through the naphthyridine unit. An alternate route to access oxomolybdates is to employ quadruply bonded [Re2Cl8]2- to oxidize cis-[Mo2(pyNP)2(OAc)2][BF4]2 (pyNP = 2-(2-pyridyl)1,8-naphthyridine). The isolated compound is the tetranuclear molybdenum cluster [Mo4Cl5O8(pyNP)2] (2). The molecular formula of compound 2 is best described as [Mo2Cl3O2(μ2-O)(η3-pyNP)][μ3-O][Mo2Cl2O2(μ2-O)2(η2-pyNP)], the fusion of two oxochlorodimolybdates linked through a μ3-oxo linkage. The oxidation of the [MoII≣MoII] unit to highly oxidized oxomolybdates and subsequent dimerization to tetranuclear core offers prospect for accessing new types of oxo-chloro-molybdenum clusters exhibiting interesting structural motifs

Novel heterobimetallic metallamacrocycles based on the 1,1‘-bis(1,8-naphthyrid-2-yl)ferrocene (FcNP2) ligand: structural characterization of the complexes [{M(FcNP<SUB>2</SUB>)}<SUB>2</SUB>]<SUP>2+</SUP>(M = Cu<SUP>I</SUP>, Ag<SUP>I</SUP>) and {MCl<SUB>2</SUB>(FcNP<SUB>2</SUB>)}<SUB>4</SUB>(M = Zn<SUP>II</SUP>, Co<SUP>II</SUP>)

Self-assembly reactions of 1,1'-bis(1,8-naphthyrid-2-yl)ferrocene (FcNP2) with CuI/AgI afford dimeric [{CuI/AgI(FcNP2)}2]2+ and with ZnCl2/CoCl2 yield tetrameric metallamacrocycles {ZnII/CoIICl2(FcNP2)}4

Tetragonal and helical morphologies from polyferrocenylsilane block polyelectrolytes via ionic self-assembly

The use of ionic self-assembly, a facile noncovalent approach, to access non-conventional block copolymer morphologies, including tetragonal and helical structures, from a combination of polyferrocenylsilane diblock copolymer polyelectrolytes and AOT-based surfactants, is described

A rare unsupported iridium(II) dimer, [IrCl<SUB>2</SUB>(CO)<SUB>2</SUB>]<SUB>2</SUB>

Oxidative additions of dichloromethanes to a diiridium(I) core, bridged by 2-ferrocenyl-1,8-naphthyridines (NP-Fc), provide an iridium(II) dimer, [IrCl2(CO)2(η1-NP-Fc)]2, featuring an unsupported Ir–Ir single bond (2.7121(8) Å)

Syntheses and reactivity studies of solvated dirhenium acetonitrile complexes

Fully and partially solvated triply-bonded [Re2]4+ complexes have been synthesized and their X-ray structures are described. A fully solvated dirhenium salt with BArf [tetrakis(3,5-bis(trifluoromethyl)phenyl)borate] as the counter anion [Re2(CH3CN)10][BArf]4 (1) has been characterized. The solubility of the complex in CH2Cl2 and THF in addition to CH3CN offers the possibility of improved reactivity. The structure of [Re2(µ-O)(CH3CN)10][BF4]4 (2) that possesses a linear [ReIII–O–ReIII]4+ unit is reported. Protonation reactions of cis-Re2Cl2(dppm)2(O2CCH3)2 and trans-Re2Cl4(dppm)2 with HBF4·Et2O in acetonitrile afforded cis and trans [Re2(dppm)2(CH3CN)6][BF4]4 (3 and 4), respectively. Prolonging the reaction time, however, does not lead to fully solvated complex [Re2(CH3CN)10][BF4]4. The neutral nitrogen donor ligands pynp (2-(2-pyridyl)-1,8-naphthyridine) and tznp (2-(2-thiazolyl)-1,8-naphthyridine) react readily with [Re2(CH3CN)10][BF4]4 to provide trans-[Re2(pynp)2(CH3CN)4][BF4]4 and trans-[Re2(tznp)2(CH3CN)4][BF4]4. The X-ray structures trans-[Re2(pynp)2(CH3CN)4][BF4]4 (5) and trans-[Re2(tznp)2(CH3CN)4][BF4]3[PF6] (6) have been determined