The reaction of bis(isopropylphosphino)methane with ruthenium carbonyl

Reaction of ⁱPrHPCH₂PHⁱPr with [Ru₃(CO)₁₂] in the presence of [(Ph₃P)₂N]CN catalyst gave sequentially [Ru₃(CO)₁₀(μ-ⁱPrHPCH₂PHⁱPr)] and [Ru₃- (CO)₉(μ-H)(μ₃-ⁱPrHPCH₂PⁱPr)]. The former complex exists in two isomeric forms. The structures were determined by ¹H and ³¹P NMR spectroscopy.     

Hyponitrite complexes: Crystal and molecular structure of [Ru2(CO)4(μ-PBu2)(μ-Ph2PCH2PPh2)(μ-η-ONNOMe)]

The new trans-hyponitrite derivative complex [Ru₂(CO)₄(μ-P^tBu₂)(μ-dppm)(μ-η²-ONNOMe)] (2, dppm = Ph₂PCH₂PPh₂) was prepared by deprotonation of [Ru₂(CO)₄(μ-H)(μ-P^tBu₂)(μ-dppm)(μ-η²-ONNOMe)][BF₄] (1) with the base DBU (1.8-diazabicyclo[5.4.0]undec-7-ene). The latter complex salt has been obtained in an improved synthesis starting from the trans-hyponitrite complex [Ru₂(CO)₄(μ-H)(μ-P^tBu₂)(μ-dppm)(μ-η²-ONNO)]. Compound 2 has been characterized by spectroscopic methods as well as by X-ray diffraction and represents the first neutral complex bearing a deprotonated monoester of the hyponitrous acid as the bridging ligand.     

Alkynyl cobalt complexes. An electrochemical study

The preparation and characterisation of the complexes Co₂(CO)₅(PMe₃)(μ-η²-Me₃SiC₂CCSiMe₃) (2) and Co₂(CO)₄(PMe₃)₂(μ-η²-Me₃SiC₂CCSiMe₃) (3) are described. A comparative electrochemical study of the complexes Co₂(CO)_6−nL_n(μ-η²-Me₃SiC₂CCSiMe₃) (n=0 (1); n=1, L=PMe₃ (2); n=2, L=PMe₃ (3), PPh₂Me (4), dppa (5), dppm (6)) is presented by means of the cyclic and square-wave voltammetry techniques. Substitution of CO by phosphine ligands transforms the Co₂C₂ redox centre from a readily reducible to an easily oxidisable centre and contributes to the stabilisation of the Co–Co bond increasing the lifetime of the radical cations and anions.     

A bicarbonate bridged diruthenium(I) complex: Key evidence for the decarboxylation step in the base-assisted reduction of Ru2Cl4(CO)6

Base-assisted reduction of [Ru(CO)₃Cl₂]₂ in the presence of NP-Me₂ (2,7-dimethyl-1,8-naphthyridine) in thf provides an unsupported diruthenium(I) complex [Ru₂(CO)₄Cl₂(NP-Me₂)₂] (1). Two NP-Me₂ and four carbonyls bind at equatorial positions and two chlorides occupy sites trans to the Ru-Ru single bond. Reaction of [Ru(CO)₃Cl₂]₂, TlOTf, KOH and NP-Me₂ in acetonitrile, in a sealed container, affords a bicarbonate bridged diruthenium(I) complex [Ru₂(CO)₂(μ-CO)₂(μ-O₂COH)(NP-Me₂)₂](OTf) (2). The in situ generated CO₂ is the source for bicarbonate under basic reaction medium. Isolation of 2 validates the decarboxylation step in the base-assisted reduction of [Ru^II(CO)₃Cl₂]₂ → [Ru^I₂(CO)₄]²⁺.     

Syntheses and molecular structures of 6-halogeno-pyridin-2-olate complexes with the diruthenium(2+) core

The complexes [Ru₂(CO)₅(μ-FpyO)₂]₂ (1), [Ru₂(CO)₄(μ-ClpyO)₂]₂ (2), and [Ru₂(CO)₄(μ-BrpyO)₂]₂ (3) were prepared from Ru₃(CO)₁₂ and 6-fluoro-2-hydroxypyridine (FpyOH), 6-chloro-2-hydroxypyridine (ClpyOH) and 6-bromo-2-hydroxypyridine (BrpyOH), respectively, in hot toluene. Compounds 1-3 are coordination dimers with a cyclo-RuORuO motif. By carrying out the reaction in hot methanol, the dinuclear complexes [Ru₂(CO)₄(μ-ClpyO)₂(CH₃OH)] (4) and [Ru₂(CO)₄(μ-BrpyO)₂(CH₃OH)] (5), respectively, were obtained. Treatment of 2 and 3 with triphenylphosphane provided the complexes [Ru₂(CO)₄(μ-ClpyO)₂(PPh₃)] (6) and [Ru₂(CO)₄(μ-BrpyO)₂(PPh₃)] (7), respectively. The solid-state structures of complexes 1, 2, 4, 6, and 7 were determined by single crystal X-ray diffraction. In all cases, a head-head coordination of the two 6-halopyridinolate ligands at the core was found. In all chlorine- or bromine-containing complexes, the axial coordination site at the ruthenium atom neighbored by two Cl or Br atoms remains unoccupied due to steric shielding by the halogen atom. In the fluoropyridinolate complex 1, the same coordination site is occupied by a carbonyl ligand.     

Reactions of 2-thiopyridone rhodium(III) complexes with tertiary phosphines

The rhodium(III) complexes containing 2-thiopyridone (pySH) and its conjugate anion 2-thiopyridonato (pyS) as the only ligands, [Rh(pyS)₂(pySH)₂]Cl, [Rh(pyS)₃(pySH)], and [Rh(pyS)₃], react with the tertiary phosphines PMe₂Ph, PPh₃, Ph₂PCH₂PPh₂ (dppm), and Ph₂PCH₂CH₂PPh₂ (dppe) to give mixed pyS/tertiary phosphine complexes of the type [Rh(pyS)₃L], [Rh(pyS)₃L₂], and [Rh(pyS)₂L₂]ClO₄ where L represents a single phosphorus donor atom. These compounds were characterized mainly by ¹H and ³¹P NMR spectroscopy.     

6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

The dinuclear bis(6-X-pyridin-2-olato) ruthenium complexes [Ru₂(μ-XpyO)₂(CO)₄(PPh₃)₂] (X = Cl (4B) and Br (5B)), [Ru₂(μ-XpyO)₂(CO)₄(CH₃CN)₂] (X = Cl (6B), Br (7B) and F (8B)) and [Ru₂(μ-ClpyO)₂(CO)₄(PhCN)₂] (9B) were prepared from the corresponding tetranuclear coordination dimers [Ru₂(μ-XpyO)₂(CO)₄]₂ (1: X = Cl; 2: X = Br) and [Ru₂(μ-FpyO)₂(CO)₆]₂ (3) by treatment with an excess of triphenylphosphane, acetonitrile and benzonitrile, respectively. In the solid state, complexes 4B-9B all have a head-to-tail arrangement of the two pyridonate ligands, as evidenced by X-ray crystal structure analyses of 4B, 6B and 9B, in contrast to the head-to-head arrangement in the precursors 1-3. A temperature- and solvent-dependent equilibrium between the yellow head-to-tail complexes and the red head-to-head complexes 4A-7A and 9A, bearing an axial ligand only at the O,O-substituted ruthenium atom, exists in solution and was studied by NMR spectroscopy. Full ¹H and ¹³C NMR assignments were made in each case. Treatment of 1 and 2 with the N-heterocyclic carbene (NHC) 1-butyl-3-methylimidazolin-2-ylidene provided the complexes [Ru₂(μ-XpyO)₂(CO)₄(NHC)], X = Cl (11A) or Br (12A). An XRD analysis revealed the head-to-head arrangement of the pyridonate ligands and axial coordination of the carbene ligand at the O,O-substituted ruthenium atom. The conversion of 11A and 12A into the corresponding head-to-tail complexes was not possible.     

Chalcogenide-capped triruthenium clusters: X-ray structures of [Ru3(CO)6(μ3-CO){P(C4H3S)3}(μ-dppm)(μ3-O)] and [(μ-H)2Ru3(CO)6{P(C4H3S)3}(μ-dppm)(μ3-S)]

Treatment of [Ru₃(CO)₉{P(C₄H₃S)₃}(μ-dppm)] (1) [dppm = bis(diphenylphosphino)methane] with molecular oxygen in benzene at 60 °C affords oxo-capped [Ru₃(CO)₆(μ₃-CO){P(C₄H₃S)₃}(μ-dppm)(μ₃-O)] (2), while with elemental sulfur and selenium related chalcogenide-capped clusters [Ru₃(CO)₆(μ₃-CO){P(C₄H₃S)₃}(μ-dppm)(μ₃-E)] (3, E = S; 5, E = Se) and bis(chalcogenide) clusters [Ru₃(CO)₆{P(C₄H₃S)₃}(μ-dppm)(μ₃-E)₂] (4, E = S; 6, E = Se) result. Reaction of 1 with H₂S in refluxing THF affords the previously reported [(μ-H)₂Ru₃(CO)₇(μ-dppm)(μ₃-S)] (7) together with the new sulfido-capped dihydride [(μ-H)₂Ru₃(CO)₆{P(C₄H₃S)₃}(μ-dppm)(μ₃-S)] (8). All new compounds have been characterized by spectroscopic data, and 2 and 8 by single-crystal X-ray diffraction analyses. Oxo-capped 2 consists of a triangular ruthenium framework capped on opposite sides by oxo and carbonyl groups, while 8 consists of a ruthenium triangle by a capping sulfido ligand and two inequivalent bridging hydride ligands.     

Synthesis and structural investigations of bulky imino- and amido-phosphine palladium dimers

The reactions of palladium(II) dimers [Pd₂Br₂(L1)₂] and [Pd₂Br₂(L2)₂] (where L1⁻ is [Ph₂PCHC(Ph)N(2,6-ⁱPr₂C₆H₃)]⁻ and L2⁻ is [Ph₂PCHC(Ph)N(2,6-Me₂C₆H₃)]⁻) with AgBF₄ in a mixture of CH₂Cl₂ and MeOH give palladium(I) dimers [Pd₂(HL1)₂][BF₄]₂ and [Pd₂(HL2)₂][BF₄]₂, respectively. These exhibit unusual coordination geometries of the metal centre. Density functional theory (DFT) calculations showed that a phenyl ring of the bridging phosphine is involved in bonding via a delocalised metal-phosphine–phenyl interaction. The remarkable kinetic stability of these palladium(I) species may explain the early termination steps in the CO/ethylene copolymerisation reaction catalysed by Pd(II)–amidophosphines or enolisable Pd(II)–iminophosphines.     

Linear and bent oxo-bridged dinuclear rhenium(V) complexes with terminal and bridging pyrazole ligands

The [ReOX₃(AsPh₃)(OAsPh₃)] (X = Cl or Br) complexes react with two equivalents of 3,5-dimetylopyrazole (3,5-Me₂pzH) in acetone at room temperature to give [{Re(O)X₂(3,5- Me₂pzH)₂}₂(μ-O)] (1 and 2). In the case of [ReOBr₃(AsPh₃)(OAsPh₃)], a small quantity of the dinuclear rhenium complex [{Re(O)Br(3,5-Me₂pzH)}₂(μ-O)(μ-3,5-Me₂pz)₂] (3) has been isolated next to the main product 2. Treatment of [ReOX₃(PPh₃)₂] compounds with two equivalents of 3,5-Me₂pzH in acetone at room temperature leads to the isolation of symmetrically substituted dinuclear rhenium complexes [{Re(O)X(PPh₃)}₂(μ-O)(μ-3,5-Me₂pz)₂] (4 and 5). Refluxing of [ReO(OEt)X₂(PPh₃)₂] complexes with 3,5-Me₂pzH in ethanol affords unsymmetrically substituted dinuclear rhenium [{Re(O)X(PPh₃)}(μ-O)(μ-3,5-Me₂pz)₂{Re(O)X(3,5- Me₂pzH)}] complexes (6 and 7). The complexes obtained in these reactions have been characterised by IR, UV-Vis, ¹H and ³¹P NMR. The crystal and molecular structures have been determined for 1, 2, 3, 4, 6 and 7 complexes.     

Generation of trans-dioxoruthenium(VI) porphyrins: A photochemical approach

trans-Dioxoruthenium(VI) porphyrin complexes have been developed as one of the best-characterized model systems for heme-containing enzymes. Traditionally, this type of compounds can be prepared by oxidation of ruthenium(II) precursors with peroxyacids and other terminal oxidants under different conditions, depending on the porphyrin ligands. In this work, a new photochemical generation of trans-dioxoruthenium(VI) porphyrins has been developed by extension of the known photo-induced ligand cleavage reactions. Refluxing ruthenium(II) carbonyl porphyrins [Ru^II(Por)(CO)] in carbon tetrachloride afforded dichlororuthenium(IV) complexes [Ru^IV(Por)Cl₂]. Facile exchange of the counterions in [Ru^IV(Por)Cl₂] with Ag(ClO₃) or Ag(BrO₃) gave the corresponding dichlorate [Ru^IV(Por)(ClO₃)₂] or dibromate [Ru^IV(Por)(BrO₃)₂] salts. Visible-light photolysis of the photo-labile porphyrin-ruthenium(IV) dichlorates or dibromates resulted in homolytic cleavage of the two O-Cl or O-Br bonds in the axial ligands to produce trans-dioxoruthenium(IV) species [Ru^VI(Por)O₂] bearing different porphyrin ligands.     

Interactions of bis-[μ-chloro-chlorotricarbonylruthenium(II)] and poly-[μ-dichloro-dicarbonylruthenium(II)] with nucleosides

The interactions of dimeric complex bis-[μ-chloro-chlorotricarbonylruthenium(II)], [Ru(CO)₃Cl₂]₂, and the polymeric complex poly-[μ-dichlorodicarbonylruthenium(II)], [Ru(CO)₂Cl₂]_x, with nucleosides (Nucl) in a 1:1 Ru:Nucl molar ratio for the dimer and 1:2 Ru:Nucl for the polymer, resulted in formation of the monomeric mononucleoside [Ru(CO)₃(Nucl)Cl₂] and bis-nucleoside [Ru(CO)₂(Nucl)₂Cl₂] complexes, respectively. The dimer [Ru(CO)₃Cl₂]₂ also gave the ionic bis-nucleoside complexes [Ru(CO)₃(Nucl)₂Cl]Cl in the molar ratio 1:2 Ru:Nucl. The mononucleoside complexes are stable in solution while the bis-nucleoside complexes tend to lose one nucleoside in strong complexing solvents, probably by solvent substitution. The complexes [Ru(CO)₃(Nucl)Cl₂] and [Ru(CO)₂(Nucl)₂Cl₂] with one N(1)H ionizable imino proton undergo ionization in alkaline solution and the complexes [Ru(CO)₃(NuclH⁺)Cl] and [Ru(CO)₂(NuclH⁺)₂], respectively, were isolated. In these deprotonated complexes the nucleosides behave as bidentate ligands, while in the protonated ones they act as monodentate. All Complexes were characterized by elemental analyses and various spectroscopic methods.     

Sn-S and Ru-Ru bonds cleavage reactions between [Ph3SnS(CH2)3SSnPh3] and Ru3(CO)12: X-ray crystal structures of [Ph3SnS(CH2)3SSnPh3] and trans-[Ru(CO)4(SnPh3)2]

The organotin complex [Ph₃SnS(CH₂)₃SSnPh₃] (1) was synthesized by PdCl₂ catalyzed reaction between Ph₃SnCl and disodium-1,3-propanedithiolate which in turn was prepared from 1,2-propanedithiol and sodium in refluxing THF. Reaction of 1 with Ru₃(CO)₁₂ in refluxing THF affords the mononuclear complex trans-[Ru(CO)₄(SnPh₃)₂] (2) and the dinuclear complex [Ru₂(CO)₆(μ-κ²-SCH₂CH₂CH₂S)] (3) in 20 and 11% yields, respectively, formed by cleavage of Sn-S bond of the ligand and Ru-Ru bonds of the cluster. Treatment of pymSSnPPh₃ (pymS = pyrimidine-2-thiolate) with Ru₃(CO)₁₂ at 55-60 °C also gives 2 in 38% yield. Both 1 and 2 have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis.     

New ruthenium complexes from Ru3(CO)12 and 6-Alkyl- or 6-Phenyl-2-hydroxypyridines

Trirutheniumdodecacarbonyl (Ru₃(CO)₁₂) reacts with 2-hydroxy-6-methylpyridine and with 2-hydroxy-5,6,7,8-tetrahydroquinoline in toluene to form centrosymmetric tetranuclear complexes of the type [Ru(η², μ-L)(CO)₂(μ₃-L)Ru(CO)₂]₂, where L is the respective (N,O)-pyridonate ligand (2 and 3). The structures of these complexes, which are almost insoluble in all common solvents, could be determined by single-crystal X-ray diffraction. Reaction of Ru₃(CO)₁₂ with 2-hydroxy-4,6-diphenylpyridine in methanol includes ortho-metallation at the phenyl ring, furnishing the dinuclear complex [Ru(κ²N,C-L)(CO)₂(μ-OCH₃)₂Ru(CO)₂ (κ²N,C-L)] (4), where L = (2-(6-hydroxy-4-phenylpyridin-2-yl)phenyl), according to an X-ray crystal structure determination.     

Dinuclear ruthenium sawhorse-type complexes containing carboxylato bridges and ferrocenyl substituents: Synthesis and electrochemistry

The ferrocenyl-containing diruthenium complexes [Ru₂(CO)₄(μ₂-η²-OOCFc)₂L₂] (Fc = ferrocenyl, fc = ferrocen-1,1′-diyl; 1: L = NC₅H₄-COOC₆H₄-OC₁₀H₂₁, 2: L = NC₅H₄-COOC₆H₄-OC₁₆H₃₃, 3: L = NC₅H₄-OOC-fc-C₁₂H₂₅) and [Ru₂(CO)₄(μ₂-η²-OOC₆H₅)₂(NC₅H₄-OOC-fc-C₁₂H₂₅)₂] (4) have been synthesized from Ru₃(CO)₁₂, ferrocene carboxylic or benzoic acid and the corresponding pyridine derivative. The synthesis of the new pyridine derivative NC₅H₄-OOC-fc-C₁₂H₂₅ used for the preparation of 3 and 4 is also reported. Complexes 1-4 posses a so-called sawhorse structure consisting of the Ru₂(CO)₄ backbone and two bridging carboxylato ligands, while the coordination sphere around the ruthenium atoms is completed by the pyridine-derived ligands bonded in the axial positions. The electrochemical behavior of 1-4 and their known analogues [Ru₂(CO)₄(μ₂-η²-OOCFc)₂L₂] (5: L = NC₅H₅, 6: L = P(C₆H₅)₃, 7: L = NC₅H₄-OOCFc) has been studied by voltammetry on rotating disc electrode and by cyclic voltammetry.     

A 31P1H NMR study of the reactions of [Rh2(μ-Cl)2(cod)2] with unsymmetrical,bidentate ligands and hydrogen

[Rh₂(μ-Cl)₂(cod)₂] reacts with Ph₂PCH₂CH₂OMe (PC₂O), Ph₂P(CH₂)₃NMe₂ (PC₃N), PBuⁿPh₂ or PPh₃ to give [Rh(cod)L₂]Cl (L = PC₂O, PC₃N, PBuⁿPh₂, PPh₃). In the presence of hydrogen, [Rh(cod)L₂]Cl is converted to [RhClH₂L₃]. In contrast, [Rh(cod)(PC₂O)₂]BPh₄ reacts with H₂ to give [RhH₂(PC₂O)₂S₂]BPh₄ (S = solvent). With Ph₂PCH₂CH₂NMe₂ (PC₂N) or Ph₂PCH₂CH₂SMe (PC₂S), [Rh₂(μ-Cl)₂(cod)₂] reacts to form the chelate complexes cis- [Rh(PC₂N)₂]⁺ or cis-[Rh(PC₂S)₂]⁺, neither of which reacts with hydrogen under ambient conditions. The products of the reactions are characterized in situ by ³¹P¹H NMR spectroscopy.     

Low temperature matrix photochemistry of M2(CO)4(μ-S-t-Bu)2 and [M(CO)2Cl2] anions, where M = Rh and Ir

Photolysis of M₂(CO)₄(μ-S-t-Bu)₂, where M = Rh or Ir, in Nujol matrices at ca. 90 K results in simple CO loss to form a tricarbonyl intermediate analogous to that observed for Rh₂(CO)₄(μ-Cl)₂. Photolysis of the anions, [M(CO)₂Cl₂]¹⁻, where M = Rh or Ir, in inert ionic matrices at ca. 90 K, results in CO-loss to form an intermediate analogous to that formed by Rh(CO)₂(i-Pr₂HN)Cl. Finally, photolysis of trans-Ir(CO)(PMe₃)₂Cl in a Nujol matrix at ca. 90 K gives rise to a new species whose carbonyl band is shifted slightly down in energy as has been observed for trans-Rh(CO)(PMe₃)₂Cl. In all cases the iridium compounds behave similarly to the rhodium species although the photon energy for iridium photochemistry is typically above that of the rhodium compounds.     

[Co{Ph2P(O)CH2P(O)Ph2}3][CoCl4] · 8CHCl3: Crystal structure and formation from [Co2(Ph2PCH2PPh2)(CO)6] in chloroform

When a solution of [Co₂(Ph₂PCH₂PPh₂)(CO)₆] in chloroform or deuterochloroform is allowed to stand in air at room temperature, it deposits dark green crystals of [Co{Ph₂P(O)CH₂P(O)Ph₂}₃][CoCl₄] · 8CHCl₃. The same product is formed more quickly and in much higher yield (80% based on Co) if the reaction is carried out in the presence of 2 equiv. of [Ph₂PCH₂PPh₂]; the Co^II appears to catalyse the air-oxidation of [Ph₂PCH₂PPh₂]. The salt was characterised by X-ray crystallography and shown to contain octahedral Co^II cations and Co^II tetrahedral anions having normal bond lengths and angles.     

(C5Me5)2NbBH4, a new reagent for the synthesis of Ru and Co carbonyl clusters with interstitial boron or carbon

The reaction of Cp*₂NbBH₄ (Cp* = η⁵-C₅Me₅) with Ru₃(CO)₁₂ gave a mixture of compounds, from which only [Cp*₂Nb(CO)₂]₂[Ru₆(CO)₁₆C] (1) could be characterized by spectroscopic and crystallographic methods. ¹¹B NMR spectroscopy proved that interstitial boron may be present in other Ru₆ clusters, but these compounds did not crystallize. The reaction of Cp*₂NbBH₄ with Co₂(CO)₈ gave among others the salts [Cp*₂Nb(CO)₂]₂[Co₆(CO)₁₅C] (4) and [Cp*₂Nb(CO)₂]₃[Co₁₃(CO)₂₄C₂] (5), which were examined by X-ray diffraction studies. The true nature of the interstitial atoms in 5 was deduced from electrochemical investigations, which reveal similar redox properties as for the already known [Co₁₃(CO)₂₄C₂]³⁻ anion.