Nucleophilic substitution reactions at the Si-Cl bonds of the dichloro(methyl)silyl ligand in five- and six-coordinate complexes of ruthenium(II) and osmium(II)

Treatment of either RuHCl(CO)(PPh₃)₃ or MPhCl(CO)(PPh₃)₂ with HSiMeCl₂ produces the five-coordinate dichloro(methyl)silyl complexes, M(SiMeCl₂)Cl(CO)(PPh₃)₂ (1a, M = Ru; 1b, M = Os). 1a and 1b react readily with hydroxide ions and with ethanol to give M(SiMe[OH]₂)Cl(CO)(PPh₃)₂ (2a, M = Ru; 2b, M = Os) and M(SiMe[OEt]₂)Cl(CO)(PPh₃)₂ (3a, M = Ru; 3b, M = Os), respectively. 3b adds CO to form the six-coordinate complex, Os(SiMe[OEt]₂)Cl(CO)₂(PPh₃)₂ (4b) and crystal structure determinations of 3b and 4b reveal very different Os-Si distances in the five-coordinate complex (2.3196(11) Å) and in the six-coordinate complex (2.4901(8) Å). Reaction between 1a and 1b and 8-aminoquinoline results in displacement of a triphenylphosphine ligand and formation of the six-coordinate chelate complexes M(SiMeCl₂)Cl(CO)(PPh₃)(κ²(N,N)-NC₉H₆NH₂-8) (5a, M = Ru; 5b, M = Os), respectively. Crystal structure determination of 5a reveals that the amino function of the chelating 8-aminoquinoline ligand is located adjacent to the reactive Si-Cl bonds of the dichloro(methyl)silyl ligand but no reaction between these functions is observed. However, 5a and 5b react readily with ethanol to give ultimately M(SiMe[OEt]₂)Cl(CO)(PPh₃)(κ²(N,N-NC₉H₆NH₂-8) (6a, M = Ru; 6b, M = Os). In the case of ruthenium only, the intermediate ethanolysis product Ru(SiMeCl[OEt])Cl(CO)(PPh₃)(κ²(N,N-NC₉H₆NH₂-8) (6c) was also isolated. The crystal structure of 6c was determined. Reaction between 1b and excess 2-aminopyridine results in condensation between the Si-Cl bonds and the N-H bonds with formation of a novel tridentate “NSiN” ligand in the complex Os(κ³(Si,N,N)-SiMe[NH(2-C₅H₄N)]₂)Cl(CO)(PPh₃) (7b). Crystal structure determination of 7b shows that the “NSiN” ligand coordinates to osmium with a “facial” arrangement and with chloride trans to the silyl ligand.     

Heterolytic CH-bond activation in the synthesis of Ni{(2-aryl-κC)pyridine-κN}2 and derivatives

Thermolysis of Ni(OTf)₂ in 2-phenyl-pyridine or 2-tolyl-pyridine afforded the cationic chelate derivatives, [bis(2-aryl-pyridine)Ni{(2-aryl-κC²)pyridine-κN}]OTf (aryl = phenyl, 1a; tolyl, 1b). Addition of KBr to 1a and LiBr to 1b provided the bromides, (2-aryl-pyridine)BrNi{(2-aryl-κC²)pyridine-κN} (aryl = phenyl, 2a; tolyl, 2b). When subjected to KO^tBu in Et₂O, the bromides generated the entitled bis-cyclometalated compounds, Ni{(2-aryl-κC²)pyridine-κN}₂ (aryl = phenyl, 3a; tolyl, 3b). These compounds insert diphenylacetylene into one cyclometalate arm to produce [(2-aryl-κC²)pyridine-κN]Ni[2-(2-(1,2-diphenylethenyl-κC²)aryl)pyridine-κN] (aryl = phenyl, 4a; p-tolyl, 4b). X-ray crystallographic studies were conducted on 1a, 2a, 3a and 4a, and a brief DFT study of 3a confirmed its low spin configuration and rippled geometry.     

Ruthenium vinylidene and carbyne complexes containing a multifunctional tridentate ligand with a PNN donor set

The neutral, octahedral ruthenium vinylidene complexes mer,trans-[(PNN)Cl₂Ru(CCHR)] (PNN = N-(2-diphenylphosphinobenzylidene)-2-(2-pyridyl)ethylamine; R = Ph, 1a; R = ^tBu, 1b) are reported. An X-ray crystallographic study of 1a confirms the tridentate, meridional coordination mode of the PNN ligand. Compounds 1a and 1b undergo regioselective electrophilic addition with HBF₄ · Et₂O at C_β of the vinylidene ligand at low temperatures, and are cleanly and quantitatively converted to the ruthenium carbynes mer,trans-[(PNN)Cl₂Ru(CCH₂R)][BF₄] (R = Ph, 2a; R = ^tBu, 2b). Carbynes 2a and 2b are stable only at low temperatures (<−50 °C). Complex 1a undergoes ligand substitution with L to yield mer,trans-[(PNN)Cl₂Ru(L)] (L = MeCN, 3a; L = CO, 3b).     

Synthesis and structures of CpFe(CO)2(κE-ECS2Ph) and [CpFe(CO)(κS,E-ECS2Ph)] (E = S,Se)

The iron trithiocarbonato complex CpFe(CO)₂(κS-SCS₂Ph) (1a) and its selenodithiocarbonato analogue CpFe(CO)₂(κSe-SeCS₂Ph) (1b) were generated by room temperature reactions of (μ-E_x)[CpFe(CO)₂]₂ (E = S; x = 2, 3. E = Se; x = 1) with PhSC(S)Cl. These compounds can be converted into the complexes CpFe(CO)(κ²S,E-ECS₂Ph) [E = S (2a), Se (2b)], in which the trithiocarbonato or the selenodithiocarbonato ligand is bonded to the iron in a chelate form, under photolytic conditions. The composition and structure of all products have been verified by elemental analyses, IR and ¹H NMR spectroscopies. The crystal structures for compounds 1a, 1b, and 2b show a three-legged piano-stool configuration at Fe in each complex. The spectroscopic and structural data in this work are commensurate with the electronic factor of the S- and Se-donor ligands.     

Synthesis, characterization, reactivity and computational studies of new rhenium(I) complexes with thiosemicarbazone ligands derived from 4-(methylthio)benzaldehyde

N-thioamide thiosemicarbazone derived from 4-(methylthio)benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in methanol gave the adducts [ReX(CO)₃(HLⁿ)] (1a X = Cl, n = 1; 1a′ X = Br, n = 1; 1b X = Cl, n = 2; 1b′ X = Br, n = 2; 1c X = Cl, n = 3; 1c′ X = Br, n = 3) in good yield.All the compounds have been characterized by elemental analysis, mass spectrometry (ESI), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³, HL³·(CH₃)₂SO and 1b′·H₂O were also elucidated by X-ray diffraction. In 1b′, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms (κS,N³) forming a five-membered chelate ring, as well as three carbonyl and bromide ligands. The resulting coordination polyhedron can be described as a distorted octahedron.The structure of the dimers is based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆] (2a), [Re₂(L²)₂(CO)₆] (2b) and [Re₂(L³)₂(CO)₆] (2c) as determined by X-ray studies. Methods of synthesis were optimized to obtain amounts of these thiosemicarbazonate complexes. In these compounds the dimer structures are achieved by Re-S-Re bridges, where S is the thiolate sulphur from a κS,N³-bidentate thiosemicarbazonate ligand.Some single crystals isolated in the synthesis of 2b contain [Re(L⁴)(L²)(CO)₃] (3b) where L⁴ (=2-methylamine-5-(para-methylsulfanephenyl)-1,3,4-thiadiazole) is originated in a cyclization process of the thiosemicarbazone. Furthermore, the rhenium atom is coordinate by the sulphur and the thioamidic nitrogen of the thiosemicarbazonate (κS,N²) affording a four-membered chelate ring.     

Carbonyl complexes of manganese, rhenium and molybdenum with 2-pyridylimino acid ligands

[MBr(CO)₃{κ²(N,O)-pyca}] [M = Mn(1a), Re(1b), pyca = pyridine-2-carboxaldehyde] and [MoCl(η³-C₃H₄Me-2)(CO)₂{κ²(N,O)-pyca}] (1c) react with aminoacid β-alanine to give the corresponding iminopyridine complexes 2a-2c. The same method affords the iminopyridine derivatives from γ-aminobutyric acid (GABA) (3a-3c) and 3-aminobenzoic acid (4a-4c). For complexes 2a-2c, 3a, 3c and 4a, the solid state structures have been determined by X-ray crystallography, revealing interesting differences in their hydrogen-bonding patterns in solid state.     

Preparation of phosphinoferrocene carboxamides from isocyanates. Synthesis and structural characterisation of palladium(II) and platinum(II) complexes with 1′-(diphenylphosphino)-1-(N-phenylcarbamoyl)ferrocene

The reaction of in situ generated 1′-(diphenylphosphino)-1-lithioferrocene with isocyanates RNCO affords the respective phosphino-carboxamides Ph₂PfcCONHR (fc = ferrocene-1,1′-diyl, R = cyclohexyl (2), and Ph (3)) in moderate yields. The coordination behaviour of 3 chosen as a representative was studied in palladium(II) and platinum(II) complexes. Depending on the metal precursor and the reaction conditions, the following compounds featuring this ligand as a P-monodentate or an O,P-chelating donor were isolated and characterised by spectroscopic methods (IR, multinuclear NMR and electrospray ionisation MS): trans-[PdCl₂(3-κP)₂] (5), trans-[PtCl₂(3-κP)₂] (6), cis-[PtCl₂(3-κP)₂] (7), [SP-4-4]-[(L^NC)PdCl(3-κP)] (8; L^NC = 2-[(dimethylamino-κN)methyl]phenyl-κC¹), and [SP-4-3]-[(L^NC)PdCl(3-κ²O,P)]SbF₆ (9). Besides, the crystal structures of a phosphine oxide resulting by oxidation of 2, viz Ph₂P(O)fcCONHCy (4), and of complexes 5·2Et₂O and 9 have been determined by single-crystal X-ray diffraction analysis.     

Synthesis, structure and dynamic stereochemistry of (O → Si)-chelate N-(trifluorosilylmethyl)-[N-(S)-(1-phenylethyl)]acetamide and 1-(trifluorosilylmethyl)-2-oxoperhydroazepine: Retention of the O → Si coordination in the adduct with KF and 18-crown-6

The novel compounds, N-(trifluorosilylmethyl)-[N-(S)-(1-phenylethyl)]-acetamide (1a) and 1-(trifluorosilylmethyl)-2-oxoperhydroazepine (1b) have been prepared from the corresponding NH-compounds using ClCH₂SiCl₃/Et₃N or ClCH₂SiCl₃/(Me₃Si)₂NH followed by methanolysis or hydrolysis of the reaction mixture in the presence of Lewis bases, and then BF₃ etherate. Potassium-(18-crown-6)-(2-oxoperhydroazepinomethyl)tetrafluorosilicate (2) was synthesized by reaction of the trifluoride (1b) with KF in the presence of 18-crown-6. Using ¹⁹F, ²⁹Si NMR and X-ray diffraction techniques it was established that the silicon atom is pentacoordinate in the trifluorides (1a, b) and hexacoordinate in the adduct 2. Thus the internal coordination of the O → Si bond present in the trifluoride (1b) is retained in the adduct 2.The stereochemical non-rigidity of the trifluorides (1a, b) and the N-(trifluorosilylmethyl)-N-methylacetamide (1c) was investigated using dynamic ¹⁹F NMR spectroscopy. The activation barriers for permutational isomerization are in the range 9.5-10 kcal mol⁻¹. Lower values of ΔG^# for permutation of trifluorides (1a-c) compared to the monofluorides with the coordination core OSiC₃F together with small negative values for the activation entropy implies a non-dissociative mechanism. Quantum-chemical analysis suggests a mechanism involving a turnstile rotation.     

Structural studies of phosphor-1,1-diselenoato Mn(I) and Re(I) complexes

Mononuclear complexes of the type, M(CO)₄[Se₂P(OR)₂] (M = Mn, R = ⁱPr, 1a; Et, 1b; M = Re, R = ⁱPr, 3a; Et, 3b) can be prepared from either [-Se(Se)P(OⁱPr)₂]₂ (A) or [Se{-Se(Se)P(OEt)₂}₂] (B) with M(CO)₅Br. O,O′-dialkyl diselenophosphate ([(RO)₂PSe₂]^-, abbreviated as dsep) ligands generated from A and B act as a chelating ligand in these complexes. Upon refluxing in acetonitrile, these mononuclear complexes yield dinuclear complexes with a general formula of [M₂(CO)₆{Se₂P(OR)₂}₂] (M = Mn, R = ⁱPr, 2a; Et, 2b; M = Re, R = ⁱPr, 4a; Et, 4b). Dsep ligands display a triconnective, bimetallic bonding mode in the dinuclear compounds and this kind of connective pattern has never been identified in any phosphor-1,1-diselenoato metal complexes. Compounds 2b, 3b, and 4 are structurally characterized. Compounds 2b and 3b display weak, secondary Se?Se interactions in their lattices.     

Reactivity of a triruthenium alkenyl cluster complex with conjugated diynes: Coupling of two diyne molecules via a face-capping diyne intermediate

The cluster [Ru₃(μ₃-κ²-HNNMe₂)(μ-κ²-PhCHCPh)(μ-CO)₂(CO)₆], which has a face-capping 1,1-dimethylhydrazido and an edge-bridging 1,2-diphenylethenyl ligand, reacts with diphenylbutadiyne or 2,4-hexadiyne to give the isomeric triruthenium carbonyl cluster complexes [Ru₃(μ₃-κ²-HNNMe₂)(μ-κ²-PhCHCPh){μ₃-κ⁴-RCCCC(R)C(R)CCCR}(CO)₆] (3a, R = Ph; 3b, R = Me) and [Ru₃(μ₃-κ²-HNNMe₂)(μ-κ²-PhCHCPh){μ₃-κ⁴-RCCCC(R)C(CCR)CR}(CO)₆] (4a, R = Ph; 4b, R = Me). These compounds contain a large unsaturated hydrocarbyl ligand that arises from a metal-cluster-mediated head-to-head (3) or head-to-tail (4) coupling of two diyne molecules and maintain the original hydrazido and ethenyl ligands. Metal clusters that contain a face-capping diyne coordinated through only one alkyne fragment, such as [Ru₃(μ₃-κ²-HNNMe₂)(μ-κ²-PhCHCPh)(μ₃-κ²-RCCCCR)(CO)₇], have also been isolated (2a, R = Ph; 2b, R = Me). They are the intermediates that incorporate a second diyne reagent to give 3 and 4. The structural parameters of intermediate 2b have been obtained from DFT calculations.     

Reactions of Mo(II)-tetraphosphine complex [MoCl2{meso-o-C6H4(PPhCH2CH2PPh2)2}] with a series of small molecules

Reactions of Mo(II)-tetraphosphine complex [MoCl₂(κ⁴-P4)] (2; P4 = meso-o-C₆H₄(PPhCH₂CH₂PPh₂)₂) with a series of small molecules have been investigated. Thus, treatment of 2 with alkynes RCCR′ (R = Ph, R′ = H; R = p-tolyl, R′ = H; R = Me, R′ = Ph) in benzene or toluene gave neutral mono(alkyne) complexes [MoCl₂(RCCR′)(κ³-P4)] containing tridentate P4 ligand, which were converted to cationic complexes [MoCl(RCCR′)(κ⁴-P4)]Cl having tetradentate P4 ligand upon dissolution into CDCl₃ or CD₂Cl₂. The latter complexes were available directly from the reactions of 2 with the alkynes in CH₂Cl₂. On the other hand, treatment of 2 with 1 equiv. of XyNC (Xy = 2,6-Me₂C₆H₃) afforded a seven-coordinate mono(isocyanide) complex [MoCl₂(XyNC)(κ⁴-P4)] (7), which reacted further with XyNC to give a cationic bis(isocyanide) complex [MoCl(XyNC)₂(κ⁴-P4)]Cl (8). From the reaction of 2 with CO, a mono(carbonyl) complex [MoCl₂(CO)(κ⁴-P4)] (9) was obtained as a sole isolable product. Reaction of 9 with XyNC afforded [MoCl(CO)(XyNC)(κ⁴-P4)]Cl (10a) having a pentagonal-bipyramidal geometry with axial CO and XyNC ligands, whereas that of 7 with CO resulted in the formation of a mixture of 10a and its isomer 10b containing axial CO and Cl ligands. Structures of 7 and 9 as well as [MoCl(XyNC)₂(κ⁴-P4)][PF₆](8′) and [MoCl(CO)(XyNC)(κ⁴-P4)][PF₆] (10a′) derived by the anion metathesis from 8 and 10a, respectively, were determined in detail by the X-ray crystallography.     

The cyclopalladation reaction of 2-phenylaniline revisited

2-Phenylaniline reacted with Pd(OAc)₂ in toluene at room temperature for 24 h in a one-to-one molar ratio and with the system PdCl₂, NaCl and NaOAc in a 1 (2-phenylaniline):1 (PdCl₂):2 (NaCl):1 (NaOAc) molar ratio in methanol at room temperature for one week to give the dinuclear cyclopalladated compounds (μ-X)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}]₂ [1a (X = OAc) and 1b (X = Cl)] in high yield. Moreover, the reaction between 2-phenylaniline and Pd(OAc)₂ in one-to-one molar ratio in acid acetic at 60 °C for 4 h, followed by a metathesis reaction with LiBr, allowed isolation of the dinuclear cyclopalladated compound (μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}]₂ (1c) in moderate yield. A parallel treatment, but using monodeuterated acetic acid (DOAc) as solvent in the cyclopalladation reaction, allowed isolation of a mixture of compounds 1c, 1c_d1 [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄](μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)-3-d-C₆H₃] and 1c_d2 (μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)-3-d-C₆H₃}]₂ in moderate yield and with a deuterium content of ca. 60%. 1a and 1b reacted with pyridine and PPh₃ affording the mononuclear cyclopalladated compounds [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(X)(L)] [2a (X = OAc, L = py), 2b (X = Cl, L = py), 3a (X = OAc, L = PPh₃) and 3b (X = Cl, L = PPh₃)] in a yield from moderate to high. Furthermore, 1a reacted with Na(acac) · H₂O to give the mononuclear cyclopalladated compound 4 [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(acac)] in moderate yield. ¹H NMR studies in CDCl₃ solution of 2a, 2b, 3a, 3b and 4 showed that 2a and 3a presented an intramolecular hydrogen bond between the acetato ligand and the amino group, and were involved in a dynamic equilibrium with water present in the CDCl₃ solvent; and that the enantiomeric molecules of 2b and 4 were in a fast exchange at room temperature, while they were in a slow exchange for 2a, 3a and 3b. The X-ray crystal structures of 3b and 4 were determined. 3b crystallized in the triclinic space group with a = 9.9170(10), b = 10.4750(10), c = 12.0890(10) Å, α = 98.610(10)°, β = 94.034(10)° and γ = 99.000(10)° and 4 in the monoclinic space group P2₁/a with a = 11.5900(10), b = 11.2730(10), c = 12.2150(10) Å, α = 90°, β = 107.6560(10)° and γ = 90°.     

Aqueous syntheses of [(Cp-R)M(CO)3] type complexes (Cp = cyclopentadienyl, M = Mn, Tc, Re) with bioactive functionalities

We describe reactions of [^99mTc(H₂O)₃(CO)₃)]⁺ (1) with Diels-Alder products of cyclopentadiene such as “Thiele’s acid” (HCp-COOH)₂ (2) and derivatives thereof in which the corresponding [(Cp-COOH)^99mTc(CO)₃)] (3) complex did form in water. We propose a metal mediated Diels-Alder reaction mechanism. To show that this reaction was not limited to carboxylate groups, we synthesized conjugates of 2 (HCp-CONHR)₂ (4a-c) (4a, R = benzyl amine; 4b, R = N_α-Boc-l-2,3-diaminopropionic acid and 4c, R = glycine). The corresponding ^99mTc complexes [(4a)^99mTc(CO)₃)] 6a, [(4b)^99mTc(CO)₃)] 6b and [(4c)^99mTc(CO)₃)] 6c have been prepared along the same route as for Thiele’s acid in aqueous media demonstrating the general applicability of this synthetic strategy. The authenticity of the ^99mTc complexes on the no carrier added level have been confirmed by chromatographic comparison with the structurally characterized manganese or rhenium complexes.Studies of the reaction of 1 with Thiele’s acid bound to a solid phase resin demonstrated the formation of [(Cp-COOH)^99mTc(CO)₃)] 3 in a heterogeneous reaction. This is the first evidence for the formation of no carrier added ^99mTc radiopharmaceuticals containing cyclopentadienyl ligands via solid phase syntheses. Macroscopically, the manganese analogue 5a and the rhenium complexes 5b-c have been prepared and characterized by IR, NMR, ESI-MS and X-ray crystallography for 5a (monoclinic, P2₁/c, a = 9.8696(2) Å, b = 25.8533(4) Å, c = 11.8414(2) Å, β = 98.7322(17)°) in order to unambiguously assign the authenticity of the corresponding ^99mTc complexes.     

1-Methyl-4-ferrocenylmethyl-3,5-diphenylpyrazole: A versatile ligand for palladium(II) and platinum(II)

The syntheses and characterization of two novel ferrocene derivatives containing 3,5-diphenylpyrazole units of general formula [1-R-3,5-Ph₂-(C₃N₂)-CH₂-Fc] {Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄) and R = H (2) or Me (3)} together with a study of their reactivity with palladium(II) and platinum(II) salts or complexes under different experimental conditions is described. These studies have allowed us to isolate and characterize trans-[Pd{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}₂Cl₂] (4a) and three different types of heterodimetallic complexes: cis-[M{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}Cl₂(dmso)] {M = Pd (5a) or Pt (5b)}, the cyclometallated products [M{κ²-C,N-[3-(C₆H₄)-1-Me-5-Ph-(C₃N₂)]-CH₂-Fc}Cl(L)] with L = PPh₃ and M = Pd (6a) or Pt (6b) or L = dmso and M = Pt (8b) and the trans-isomer of [Pt{1-Me-3,5-Ph₂-(C₃N₂)-CH₂-Fc]}Cl₂(dmso)] (7b). In compounds 4a, 5a, 5b and 7b, the ligand behaves as a neutral N-donor group; while in 6a, 6b and 8b it acts as a bidentate [C(sp²,phenyl),N(pyrazole)]⁻ group. A comparative study of the spectroscopic properties of the compounds, based on NMR, IR and UV-Visible experiments, is also reported.     

Synthesis,structure, and electrochemistry of pyridinecarboxamide cobalt(III) complexes; the effect of bridge substituents on the redox properties

Two series of complexes of the types trans-[Co^III(Mebpb)(amine)₂]ClO₄ {Mebpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-methylbenzene dianion, and amine = pyrrolidine (prldn) (1a), piperidine (pprdn) (2a), morpholine (mrpln) (3a), benzylamine (bzlan) (4a)}, and trans-[Co^III(cbpb)(amine)₂]X {cbpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-chlorobenzene dianion, and amine = pyrrolidine (prldn), X = PF₆ (1b), piperidine (pprdn), X = PF₆ (2b), morpholine (mrpln), X = ClO₄ (3b), benzylamine (bzlan), X = PF₆ (4b)} have been synthesized and characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structure of 1a has been determined by X-ray diffraction. The electrochemical behavior of these complexes, with the goal of evaluating the effect of axial ligation and equatorial substitution on the redox properties, is also reported. The reduction potential of Co^III, ranging from −0.53 V for (1a) to −0.31 V for (3a) and from −0.48 V for (1b) to −0.22 V for (3b) show a relatively good correlation with the σ-donor ability of the axial ligands. The methyl and chloro substituents of the equatorial ligand have a considerable effect on the redox potentials of the central cobalt ion and the ligand-centered redox processes.     

Pyridine- and pyrimidine-2-thiolate complexes of ruthenium

A series of mononuclear ruthenium complexes containing pyridine- and pyrimidine-2-thiolato ligands was prepared and characterized. The new compounds of general formula CpRu(PPh₃)(κ²S,N-SR) (1) (SR = pyridine-2-thiolate (a), pyrimidine-2-thiolate (b)) were prepared directly by reacting the thiolato anions (RS⁻) with CpRu(PPh₃)₂Cl. Complexes 1 readily react with NOBF₄ or CO in THF at room temperature to give [CpRu(PPh₃)(NO)(κ¹S-HSR)][BF₄]₂ (2) and CpRu(PPh₃)(CO)(κ¹S-SR) (3), respectively. The one-pot reaction of CpRu(PPh₃)₂Cl, thiolato anions and bis(diphenylphosphino)ethane (dppe) gave CpRu(dppe)(κ¹S-SR) [dppe: Ph₂PCH₂CH₂PPh₂ (4)]. The complex salts, [CpRu(PPh₃)₂(κ¹S-HSR)]BPh₄ (5) are prepared by mixing CpRu(PPh₃)₂Cl, HSR and NaBPh₄ at room temperature. The structures of CpRu(PPh₃)(κ²S,N-Spy) (1a), [CpRu(PPh₃)(NO)(κ¹S-HSpy)][BF₄]₂ (2a) and CpRu(PPh₃)(CO)(κ¹S-Spy) (3a), (py = C₅H₄N) have been determined.     

Tricarbonylrhenium(I) and manganese(I) complexes of 2-(pyrazolyl)-4-toluidine

A series of tricarbonyl rhenium(I) and manganese(I) complexes of the electroactive 2-(pyrazolyl)-4-toluidine ligand, H(pzAn^Me), has been prepared and characterized including by single crystal X-ray diffraction studies. The reactions between H(pzAn^Me) and M(CO)₅Br afford fac-MBr(CO)₃[H(pzAn^Me)] (M = Mn, 1a; Re, 1b) complexes. The ionic species {fac-M(CH₃CN)(CO)₃[H(pzAn^Me)]}(PF₆) (M = Mn, 2a; Re, 2b) were prepared by metathesis of 1a or 1b with TlPF₆ in acetonitrile. Complexes 1a and 1b partly ionize to {M(CH₃CN)(CO)₃[H(pzAn^Me)]⁺}(Br⁻) in CH₃CN but retain their integrity in less donating solvents such as acetone or CH₂Cl₂. Each of the four metal complexes reacts with (NEt₄)(OH) in CH₃CN to give poorly-soluble crystalline [fac-M(CO)₃(μ-pzAn^Me)]₂ (M = Mn, 3a; Re, 3b). The solid state structures of 3a and 3b are of centrosymmetric dimeric species with bridging amido nitrogens and with pyrazolyls disposed trans- to the central planar M₂N₂ metallacycle. In stark contrast to the diphenylboryl derivatives, Ph₂B(pzAn^Me), none of the tricarbonyl group 7 metal complexes are luminescent.     

Alkynylphosphanes as supports for mixed-metal Co4M (M = Ru, Os) fluoride complexes: Syntheses, structures and thermolysis studies

Treatment of the tetrameric group eight fluoride complexes [MF(μ-F)(CO)₃]₄ [M = Ru (1a), Os (1b)] with the alkynylphosphane, Ph₂PCCPh, results in fluoride-bridge cleavage and the formation of the air-sensitive monomeric octahedral complexes [MF₂(CO)₂(PPh₂CCPh)₂] [M = Ru (2a), Os (2b)] in high yield. The molecular structure of 2b reveals a cis, cis, trans configuration for each pair of ligands, respectively. The free alkyne moieties in 2 can be readily complexed to hexacarbonyldicobalt fragments by treatment with dicobalt octacarbonyl to afford [MF₂(CO)₂(μ-η¹:η²-PPh₂CCPh)₂{Co₂(CO)₆}₂] [M = Ru (3a), Os (3b)]. Evidence for an intramolecular non-bonded contact between a bound fluoride and a cobalt carbonyl carbon atom is seen in the molecular structure of 3a. Thermolysis of 3a at 50 °C results in fluoride dissociation to give [RuF(CO)₂(μ-η¹:η²-PPh₂CCPh)₂{Co₂(CO)₆}₂]⁺ (4), while no reaction occurred with the osmium analogue. Prolonged thermolysis at 120 °C in a sealed vessel of both 3a and 3b gave only insoluble decomposition products.     

Conversion of novel palladacycles into oxopyrrolo[3,4-b]quinolines

The quinolinylcyclopalladated complexes 3a–b were synthesised in good yields (81% and 77%) by the insertion reaction of the prepared dinuclear palladium complexes [Pd(C,N-2-C₉H₄N-CHO-3-R-6)Cl(PPh₃)]₂ [(R = H (2a), R = OMe (2b)] with isonitrile XyNC (Xy = 2,6-Me₂C₆H₃). The cyclopalladated complexes 3a–b were also obtained in low yields (39% and 33.5%) via a one pot oxidative addition reaction of quinoline chloride 1a–b with isonitrile XyNC:Pd(dba)₂ (4:1). The reactions of 3a–b with Tl(TfO) (TfO = triflate, CF₃SO₃) in the presence of H₂O or EtOH causes depalladation reactions of the complexes to provide the corresponding organic compounds 4a–b, 5a–b and 6a–b in yields (41%, 27% and 18–19%). The products were characterized by satisfactory elemental analyses and spectral studies (IR, ¹H, ¹³C and ³¹P NMR). The crystal structures of 2a, 3a and 3b were determined by X-ray diffraction studies.     

The (phosphino)tetraphenylborate ligand in ruthenium-arene chemistry

The synthesis of a series of anionic half-sandwich ruthenium-arene complexes [E][RuCl₂(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (E = Bu₄N⁺: R = Ph, 1a, ⁱPr, 1b or Cy, 1c; E = bis(triphenylphosphine)iminium or PNP⁺: R = Ph, 1a′, ⁱPr, 1b′ or Cy, 1c′) are reported. X-ray crystallographic studies of 1a′ and 1b′ confirmed the three-legged piano-stool coordination geometry. In solution, complexes 1a-c and 1a′-c′ are proposed to form monomer-dimer equilibria as a result of chloride ligand dissociation. Complexes 1a-c and 1a′-c′ also form the formally neutral zwitterionic complexes [RuCl(L)(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (L = pyridine: R = Ph, 2a, ⁱPr, 2b or Cy, 2c; L = MeCN: R = Ph, 3a, ⁱPr, 3b or Cy, 3c) via chloride ligand abstraction using AgNO₃ or MeOTf.