Cationic carbonyl complexes of manganese (I) with nitriles and dinitriles

The reaction of Mn(CO)₅OClO₃ with nitriles,L, and dinitriles,L-L, in a wide variety of conditions affords cationic pentacarbonyls, [Mn(CO)₅(L)] ClO₄ and [Mn (CO)₅(L-L)] ClO₄ and fac-tricarbonyls, [Mn (CO)₃ (L)₃] ClO₄ and [(CO) ₃Mn (μ L-L) ₃Mn (CO)₃] (ClO₄)₂     

Magnesium(I) dimers as reagents for the reductive coupling of isonitriles and nitriles

The reactivity of two β-diketiminate coordinated magnesium(I) dimers, [LMgMgL], L=[(RNCMe)(2) CH](-) , R=C(6) H(3) iPr(2) -2,6 ((Dip) Nacnac(-) ) or mesityl ((Mes) Nacnac(-) ), towards a series of isonitriles and nitriles have been examined. Reactions with the isonitriles, RN?C: (R=tBu or C(6) H(3) Me(2) -2,6 (Xyl)), led to reductive C?C couplings and the formation of [{((Dip) Nacnac)Mg}(2) {μ-(XylN=C-)(2) }] and [{((Mes) Nacnac)Mg}(2) {μ-(tBuN=C-)(2) }], or a reductive N?C cleavage and the generation of the magnesium cyanide complex, [{((Dip) Nacnac)Mg(μ-CN)}(3) ]. Reactions of the magnesium dimers with benzonitrile, PhC?N, afforded the C?C-coupled products, [((Dip) Nacnac)Mg[μ-{N=C(Ph)-}(2) ]Mg(NCPh)((Dip) Nacnac)], and [{{((Mes) Nacnac)Mg}(2) [μ-{N=C(Ph)-}(2) ]}(2) ], whereas the reductive C?C cleavage of tBuC?N gave rise to a mixture of [((Dip) Nacnac)Mg(tBu)(NCtBu)] and [{((Dip) Nacnac)Mg(μ-CN)}(3) ]. In contrast, a combination of net nitrile isomerization and C?C coupling processes was involved in the reduction of Me(3) SiC?N, which yielded [{((Dip) Nacnac)Mg}(2) {μ-(Me(3) SiN=C-)(2) }]. All new compounds were crystallographically and spectroscopically characterized. The outcomes of the reported reactions were found to be dependent upon both the steric bulk of the magnesium(I) reagent, and the nature of the isonitrile/nitrile substituent. This combined with a high degree of selectivity for the reactions, indicates that magnesium(I) dimers may find use by organic and organometallic chemists as viable alternatives to currently available reducing agents that are utilized for the reduction of unsaturated organic substrates.     

Neutral and cationic dicarbonyl complexes of manganese (I) with diphosphines

The reaction of BrMn(CO)₅ with dppm in refluxing toluene gives the neutral compunds cis-cis-BrMn(CO)₂(dppm)₂ which has been shown by ³¹P NMR spectroscopy to have one dppm monodentate and the other bidendate. This complex reacts with TIPF₆ in dichloromethane solution to give the salt cis-[Mn(CO)₂-(dppm)₂]PF₆ or, if the reaction is carried out in the presence of CO, the salt mer-[Mn(CO)₃(dppm)₂]PF₆ which also has one monodentate dppm (by ³¹P NMR). The cationic complex cis-[Mn(CO)₂(dppm)₂]⁺ isomerizes to the transisomer when irradiated with UV light, while heating of the latter gives back the cis-isomer. The perchlorate salts of the cation cis-[Mn(CO)₂(dppm)₂⁺ can be prepared by reacting fac-O₃ClOMn(CO)₃(dppm) withdppm in refluxing toluene, and trans-[Mn(CO)₂(diphos)(diphos)′]⁺, diphos or diphos′ being dppm or dppe, by treating the fac-O₃ClMn(CO)₃(diphos) with dppm or dppe under UV irradiation.     

Synthesis of cationic carbonyl complexes of manganese(I) with bidentate ligands

Summary Bidentate ligands can readily replace acetone in thefac-[Mn(CO)₃(chel)(OCMe₂)]⁺ complexes or the perchlorate group fromfac-[Mn(CO)₃(chel)(OClO₃)] yieldingfac-[Mn(CO)₃(chel)(L-L)]⁺ or [{fac-Mn(CO)₃(chel)}₂(L-L)]²⁺ [chel = 1,10-phenanthroline (phen), 2,2-bipyridine (bipy), 1,2-bis(diphenylphosphine)ethane (dpe); L-L = bis(diphenylphosphine)methane (dpm), dpe, 1,4-bis(diphenylphosphine)butane (dpb), succinonitrile (suc), and glutaronitrile (glu)]. Some of these mononuclear complexes are precursors for binuclear complexes which are linked by bridging phosphines or nitriles.     

Synthesis,formation constants and reactions of cationic rhodium(I) complexes of nitriles

Reactions of Rh(ClO₄)(CO)(PPh₃)₂ with nitriles produce new cationic rhodium(I) complexes, [RhL(CO)(PPh₃)₂]ClO₄ [L = CH₃CN (1), CH₃CH₂CH₂CN (2) or C₆H₅CN (3)], whose spectral data suggest that the nitriles are coordinated through the nitrogen atom. Formation constants for the reaction Rh(ClO₄)(CO)(PPh₃)₂ + L ⇋ [RhL(CO)(PPh₃)₂]ClO₄, have been measured to be 1.01 × 10⁵ M⁻¹ (CH₃CN), 1.07 × 10⁵ M⁻¹ (CH₃CH₂CH₂CN) and 2.59 × 10⁴ M⁻¹ (C₆H₅CN) at 25°C in monochlorobenzene. The differences in the formation constants for the different nitriles seem to be predominantly due to differences in ΔH (not to differences in ΔS). The nitriles in 1–3 are readily replaced with nitrogen base ligands (unsaturated nitriles and pyridine) and PPh₃.     

New cationic and anionic tetracoordinate nickel(I) complexes

Summary The preparation, structural study and chemical behaviour of new cationic, monoanionic and dianionic tetracoordinate nickel(I) complexes of the types: [NiL₄][BPh₄] (L=PPh₃, AsPh₃ or SbPh₃), [PR₄][NiX₂L₂] (X=Cl, Br or I; L=PPh₃, AsPh₃ or SbPh₃ and [PR₄]⁺=PPh₄, Ph₃PCH₂Ph or Ph₃PEt) and [PR₄]₂[NiX₃L] (X=Cl, Br or I; L=PPh₃ and [PR₄]⁺=PPh₄ or PPh₃CH₂Ph) are described.     

Mesomorphic complexes of rhenium(I) and manganese(I)

Abstract

Following our discovery of liquid crystals based on octahedral manganese(I), we have now extended these studies to the synthesis of what we believe to be unique examples of mesomorphic rhenium-based complexes. These complexes offer advantages over the related manganese(I) systems in that they are more thermally stable. Further, modification of the organic backbone has led to lower melting manganese materials.     

Carbonyl cationic rhodium(I) and iridium(I) complexes with sulphur donor and triphenylphosphine ligands

Summary The reaction of previously reported Rh^I and Ir^I cationic complexes towards carbon monoxide and triphenylphosphine has been studied. Carbonyl rhodium(I) mixed complexes of the formulae [Rh(CO)L₂(PPh₃)]ClO₄, (L=tetrahydrothiophene(tht), trimethylene sulfide(tms), SMe₂, or SEt₂), [(CO)(PPh₃)Rh{-(L-L)}₂Rh(PPh₃)(CO)](ClO₄)₂ (L-L= 2,2,7,7-tetramethyl-3,6-dithiaoctane (tmdto), (MeS)₂(CH₂)₃ (dth), or 1,4-dithiacyclohexane (dt), [Rh(CO)L(PPh₃)₂]ClO₄ (L= tht, tms, SMe₂, or SEt₂), and carbonyl iridium(I) complexes of the formulae [Ir(CO)₂(COD)(PPh₃)]ClO₄, [Ir(CO)(COD)(PPh₃)₂]ClO₄, [(CO)(COD)(PPh₃) Ir{-(L-L)} Ir(PPh₃)(COD)(CO)](ClO₄)₂ (L-L = tmdto or dt), [(CO)₂ (PPh₃)Ir(-tmdto)Ir(PPh₃)(CO)₂](ClO₄)₂, [(CO)₂(PPh₃) Ir(-dt)₂Ir(PPh₃)(CO)₂](ClO₄)₂, were prepared by different synthetic methods.     

Cyclometallated compounds of manganese(I) with 1-methylphenylimidazoles

Cyclometallated complexes of magnanese(I) with 1-methylphenylimidazoles have been prepared. IR and ¹H NMR spectroscopic studies show they are octahedral complexes in which the imidazole ligand is bound to the metal through the nitrogen and phenyl C(6) atoms. When the imidazole ligand with two phenyl groups at the C(2′) and C(4′) atoms is used, both possible cyclometallated compounds are obtained.     

Cationic Carbonyl complexes of manganese(I) with diphosphines

The bromo-carbonyls fac-BrMn(CO)₃(diphos)(diphos  Ph₂P(CH₂)_nPPh₂ for n = 1(dpm), 2(dpe), 3(dpp) and 4(dbp)) react with AgClO₄ in dichloromethane solution to give the neutral fac-O₃ClOMn(CO)₃(diphos). The reaction of the latter complexes at room temperature with a variety of ligands L  phosphines (PR₃), phosphites (P(OR)₃), pyridine (Py), acetonitrile (MeCN), tetrahydrothiophene (THT) or acetone (Me₂CO) leads to the cationic species fac-[Mn(CO)₃(diphos)L]ClO₄ (or to the [Mn(CO)₄(diphos))]ClO₄, when L  CO). When L is a phosphorus ligand, the cationic fac-tricarbonyls isomerize upon heating to the mer isomers, which could only be isolated by this method for diphos  dpm, the reaction being accompanied by decomposition in the other cases. UV irradiation of the mer-[Mn(CO)₃(diphos)L]ClO₄ in the presence of a large excess of L gives the corresponding trans-[Mn(CO)₂(diphos)L₂]ClO₄.     

Monocarbonyl cationic rhodium(I) complexes

Summary The preparations and characterisation of cationic complexes of the type [Rh(CO)(MeCN)(PR₃)₂]ClO₄, [Rh(CO)L(PR₃)₂]ClO₄ (L=py or 2-MeOpy), [Rh(CO)(L-L)(PR₃)₂]ClO₄ (L-L = bipy or phen) and [Rh(CO)(PR₃)₃]ClO₄ with PR₃ = P(p-YC₆H₄)₃ (Y=Cl, F, Me or MeO) are described.     

Isolated cationic crown ether complexes of gallium(I) and indium(I)

The recently reported homologous low-valent indium and gallium salts M(+)[Al(OR(F))(4)](-) (M = Ga, In; R(F) = C(CF(3))(3)) were used to extend the coordination chemistry of Ga(I) and In(I) to the isolated [18]crown-6 complexes [M([18]crown-6)(PhF)(2)](+)[Al(OR(F))(4)](-) in fluorobenzene solution (PhF = C(6)H(5)F). In contrast to known ion-paired compounds for M = In, our complexes are undisturbed and in the solid state free of contacts to the anion. A peculiar combination of very weak η(1)- and η(6)-coordination to the PhF-solvent was observed that allows speculation about the presence of a stereochemically active lone pair at M(I). Structure and energetics of these novel salts were rationalized on the basis of DFT calculations.     

Preparation and catalytic activity of cationic rhodium(I) and iridium(I) complexes with phosphine sulphide ligands

The preparation and properties of cationic rhodium and iridium complexes of types [M(diolefin)L₂](ClO₄) and [M(diolefin)L(PPh₃)](ClO₄) [M = Rh, diolefin = 1,5-cyclooctadiene (COD) or 2,5-norbornadiene; M = Ir, diolefin = COD; L = phosphine sulphide] are described. The complexes have been characterized by IR, ¹H NMR and ³¹P NMR spectroscopy. The use of [M(diolefin)L₂](ClO₄) as catalyst precursors in homogeneous hydrogenation of olefins has been studied.     

Preparation and properties of cationic trimethylphosphiterhodium(I) complexes with arene ligands

Summary The preparation and properties of cationic arenerhodium(I) complexes of general formula [Rh {P(OMe)₃}(⁶-arene)]A [arene=C₆H_6–nMe_n (n=0, 1, 2, 3, 4 or 6); A=ClO ₆ ^– , PF ₆ ^– ] are described. The coordinated arene is dissociated in (CD₃)₂ CO or DCCl₃ solution and this dissociation decreases with increased methyl substitution of the arene ligand.The ability of these cationic complexes to function as an intermediate for the synthesis of other rhodium(I) complexes by displacement of the coordinated arene with or -donor ligands has been studied.     

DNA binding and nuclease activity of cationic iron(IV) and manganese(III) corrole complexes

Cationic meso(4‐N‐methylpyridyl)‐based metallocorroles, μ‐oxo iron corrole dimer ( 1b ) and manganese corrole monomer ( 2b ), were synthesized and characterized. The interactions of these two metal corrole complexes with CT‐DNA were studied by UV–visible, fluorescence and circular dichroism spectroscopic methods, as well as by viscosity measurements. The results revealed that 1b interacts with CT‐DNA in a difunctional binding mode, i.e. non‐classical intercalation and outside groove binding with H‐aggregation, while 2b can interact with CT‐DNA via an outside groove binding mode only. The binding constants K_b of 1b and 2b were 4.71 × 10⁵ m ^?1 and 2.17 × 10⁵ m ^?1, respectively, indicating that 1b can bind more tightly to CT‐DNA than 2b . Furthermore, both complexes may cleave the supercoiled plasmid DNA efficiently in the presence of hydrogen peroxide or tert‐butyl hydroperoxide (TBHP), albeit 1b exhibited a little higher efficiency. The inhibitor tests suggested that singlet oxygen and high‐valent (oxo)iron(VI) corrole or (oxo)manganese(V) corrole might be the active intermediates responsible for the oxidative DNA scission. Copyright © 2014 John Wiley & Sons, Ltd.     

Mono and dinuclear cationic rhodium(I) and iridium(I) complexes with sulphur donor and group Vb ligands

Summary Rhodium(I) and iridium(I) mixed complexes of the formulae [M(diolefin)LL]ClO₄, [M(diolefin)L₂L]ClO₄, [(diolefin)LIr(-L)₂IrL(diolefin)](ClO₄)₂, [(diolefin)LM(-L-L)ML'(diolefin)](ClO₄)₂, [(diolefin)Rh{-(L-L)}₂Rh(PPh₃)₂](ClO₄)₂ and [(diolefin)LIr{-(L-L)}₂IrL (diolefin)](C1O₄)₂, (L=monodentate sulphur ligand, L-L=bidentate sulphur ligand, L=group Vb ligand; M=Rh, diolefin=1,5-cyclooctadiene (COD) or 2,5-norbornadiene (NBD); M=Ir, diolefin=COD) are described.Author to whom all correspondence should be directed.     

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.     

Cationic di- and mono-carbonyl complexes of manganese(I)

The complexes fac-O₃ClOMn(CO)₃(NN) (NN = 1,10-phenantroline (phen) or 2,2'bipyridine (bipy)) react with an excess of the ligands L [L = P(OR)₃ or P(OR)₂Ph, R = Me or Et] in refluxing ethanol to give cis-trans-[Mn(CO)₂-(NN)L₂]ClO₄, or the more highly substituted [Mn(CO)(NN)L₃]ClO₄ if the reaction is carried out under UV irradiation. Carbonylation at normal pressure of the latter complexes results in the formation of cis-cis-[Mn(CO)₂(NN)L₂]ClO₄, which undergo isomerization to the cis-trans isomer when heated in acetone.Treatment of fac-O₃ClOMn(CO)₃(dpe) (dpe = 1,2-bis(diphenylphosphino)-ethane] with bipy or phen in refluxing ethanol gives the corresponding cis-[Mn(CO)₂(NN)(dpe)]ClO₄ complexes, and irradiation of these with UV in the presence of an excess of P(OR)₃ (R = Ph, Et or Me) gives the monocarbonyls [Mn(CO)(NN)(dpe)L]ClO₄.