Manganese(III) complexes of N2O2 donor 5-bromosalicylideneimine ligands: Combined effects of electron withdrawing substituents and chelate ring size variations on electrochemical properties

A series of mononuclear manganese(III) complexes of formulae [Mn(L)(X)(H₂O)] (1-13) and [Mn(L)(X)] (14-17) (X = ClO₄, F, Cl, Br, I, NCS, N₃), derived from the Schiff bases of 5-bromosalicylaldehyde and different types of diamine (1,2-diaminoethane, 1,2-diaminopropane, 1,3-diaminopropane and 1,4-diaminobutane), have been synthesized and characterized by the combination of IR, UV-Vis spectroscopies, cyclic voltammetry and by X-ray crystallography. The redox properties of all the manganese(III) complexes show grossly identical features consisting of a reversible or quasireversible Mn^III/Mn^II reduction. Besides Mn^III/Mn^II reduction, the complexes 4, 5, 10, 13 and 16 also show reversible or quasireversible Mn^III/Mn^IV oxidation. A linear correlation has been found for the complexes 5, 7, 11 and 13 [Mn(L²)(X)(H₂O)] (X = F, Cl, Br, I) when E_1/2 [Mn^III/Mn^II] is plotted against Mulliken electronegativities (χ_M). The effect of the flexibility of the ligand on redox potential has been studied. It has been observed that the manganese(II) state is stabilized with increasing flexibility of the ligand environment. The crystal structure of 6 shows an octahedral geometry.     

The influence of substituents (R) at N atom of thiophene-2-carbaldehyde thiosemicarbazones {(C4H3S)HCN-N(H)-C(S)NHR} on bonding, nuclearity and H-bonded networks of copper(I) complexes

The nuclearity, bonding and H-bonded networks of copper(I) halide complexes with thiophene-2-carbaldehyde thiosemicarbazones {(C₄H₃S)HC²N³-N(H)-C¹(S)N¹HR} are influenced by R substituents at N¹ atom. Thiophene-2-carbaldehyde-N¹-methyl thiosemicarbazone (HttscMe) or thiophene-2-carbaldehyde-N¹-ethyl thiosemicarbazone (HttscEt) have yielded halogen-bridged dinuclear complexes, [Cu₂(μ-X)₂(η¹-S-Htsc)₂(Ph₃P)₂] (Htsc, X: HttscMe, I, 1; Br, 2; Cl, 3; HttscEt, I, 4; Br, 5; Cl, 6), while thiophene-2-carbaldehyde-N¹-phenyl thiosemicarbazone (HttscPh) has yielded mononuclear complexes, [CuX(η¹-S-HttscPh)₂] (X, I, 7a; Br 8; Cl, 9) and a sulfur bridged dinuclear complex, [Cu₂(μ-S-HttscPh)₂(η¹-S-HttscPh)₂I₂] 7b co-existing with 7a in the same unit cell. These results are in contrast to S-bridged dimers [Cu₂(μ-S-Httsc)₂(η¹-Br)₂(Ph₃P)₂] · 2H₂O and [Cu₂(μ-S-Httsc)₂(η¹-Cl)₂(Ph₃P)₂] · 2CH₃CN obtained for R = H and X = Cl, Br (Httsc = thiophene-2-carbaldehyde thiosemicarbazone) as reported earlier. The intermolecular CH_Ph?π interaction in 1-3 (2.797 Å, 1; 3.264 Å, 2; 3.257 Å, 3) have formed linear polymers, whereas the CH_Ph?X and N³?HCH interactions in 4-6 (2.791, 2.69 Å, 5; 2.776, 2.745 Å, 6, respectively) have led to the formation of H-bonded 2D polymer. The PhN¹H?π, interactions (2.547 Å, 8, 2.599 Å, 9) have formed H-bonded dimers only. The Cu?Cu separations are 3.221-3.404 Å (1-6).     

Reactivity of phenyldi(2-thienyl)phosphine towards group 7 metal carbonyls: Carbon-phosphorus bond activation

Addition of phenyldi(2-thienyl)phosphine (PPhTh₂) to [Re₂(CO)_10−n(NCMe)_n] (n = 1, 2) affords the substitution products [Re₂(CO)_10−n(PhPTh₂)_n] (1, 2) together with small amounts of fac-[ClRe(CO)₃(PPhTh₂)₂] (3) (n = 2). Reaction of [Re₂(CO)₁₀] with PPhTh₂ in refluxing xylene affords a mixture which includes 2, [Re₂(CO)₇(PPhTh₂)(μ-PPhTh)(μ-H)] (4), [Re₂(CO)₇(PPhTh₂)(μ-PPhTh)(μ-η¹,κ¹(S)-C₄H₃S)] (5) and mer-[HRe(CO)₃(PPhTh₂)₂] (6). Phosphido-bridged 4 and 5 are formed by the carbon-phosphorus bond cleavage of the coordinated PPhTh₂ ligand, the cleaved thienyl group being retained in the latter. Reaction of [Mn₂(CO)₁₀] with PPhTh₂ in refluxing toluene affords [Mn₂(CO)₉(PPhTh₂)] (7) and the carbon-phosphorus bond cleavage products [Mn₂(CO)₆(μ-PPhTh)(μ-η¹,η⁵-C₄H₃S)] (8) and [Mn₂(CO)₅(PPhTh₂)(μ-PPhTh)(μ-η¹,η⁵-C₄H₃S)] (9). Both 8 and 9 contain a bridging thienyl ligand which is bonded to one manganese atom in a η⁵-fashion.     

Some binuclear acetonitrile ‘solvated’ complexes of copper(I) chloride and bromide with triphenylarsine

Reaction of copper(I) chloride and bromide, CuX (X = Cl or Br), with triphenylarsine in acetonitrile solution has resulted in two adducts, respectively, of 2:3:1, [(Ph₃As)₂Cu(μ-Cl)₂Cu(AsPh₃)(NCMe)] (1), and 1:1:2 stoichiometry, [(Ph₃As)(MeCN)Cu(μ-Br)₂Cu(NCMe)(AsPh₃)] · 2MeCN (2), characterized by elemental analysis, IR, ESI MS and NMR spectroscopy, and room temperature single crystal X-ray structure determinations. The environments of the two four-coordinate copper(I) atoms in 1 are different, being As₂Cu(μ-Cl)₂ and As,NCu(μ-Cl)₂. (2) is also binuclear, being a centrosymmetric dimer with the two four-coordinate, symmetry-related copper atoms having As,NCu(μ-Br)₂-environments.     

Synthesis of (NBu4)2[Pd2(μ-Br)2(C6X5)2Br2] (X=F,Cl), new and more versatile precursors of pentahalophenyl derivatives of palladium(II)

The title compounds (1, X=F; 2, X=Cl) were obtained in quantitative yield by refluxing together (NBu₄)₂[Pd₂(μ-Br)₂(C₆X₅)₄] and (NBu₄)₂[Pd₂(μ-Br)₂Br₄]. Treatment of 1 or 2 with AgClO₄ (Pd:Ag= 1:1) gave solutions which behaved as containing ‘Pd(C₆X₅)Br’. 1, 2 and the ‘Pd(C₆X₅)Br’ solutions were checked as precursors of mono-pentahalophenyl derivatives, yielding a variety of complexes [Pd(C₆X₅)Br(L-L)] (L-L=bipy, tmen, dpe, COD), [Pd(C₆X₅)BrL₂] (L=p-TolNH₂, py, PPh₃, AsPh₃, SbPh₃), [Pd₂(μ-Br)₂(C₆X₅)₂L₂] (X=F, L=AsPh₃; X=Cl, L=SbPh₃) and (NBu₄)[Pd(C₆X₅)Br₂L] (X=F, L= py, AsPh₃, SbPh₃; X=Cl, L=p-TolNH₂, py, PPh₃, AsPh₃, SbPh₃). The solutions of ‘Pd(C₆X₅)Br’ proved to be the best general precursors of complexes [Pd(C₆X₅)BrL₂] although complexes with OPPh₃ could not be obtained.     

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.     

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.     

Phosphorus-carbon(pyridyl) bond cleavage on reacting diphenyl-2-pyridylphosphine with triiron dodecacarbonyl

The reaction of [Fe₃(CO)₁₂] with diphenyl-2-pyridylphosphine (PPh₂Py) in refluxing toluene for 1 h afforded three compounds, [Fe₂(CO)₆(μ-PPh₂)(μ-κ²-C,N-C₅H₄N)] (1), [Fe(CO)₄(κ¹-P-PPh₂Py)] (2), and [Fe(CO)₃(κ¹-P-PPh₂Py)₂] (3) in 23%, 10% and 3.5% yields after work-up, respectively. The PPh₂Py ligand acts as a terminal P-donor ligand in 2 and 3, while in 1 it underwent a selective phosphorus-carbon(pyridyl) bond cleavage to afford phosphido- and pyridyl-bridged ligands. The complexes were characterized by elemental analysis, FAB-mass, FTIR, ¹H and ³¹P-{¹H}NMR spectroscopies. Compounds 1 and 2 were also characterized by X-ray single crystal.     

Reactivity of electron-deficient triosmium quinoline cluster [Os3(CO)9(μ3-η-C9H6N)(μ-H)] with alkynes

Reactions of the electron-deficient triosmium cluster [Os₃(CO)₉(μ₃-η²-C₉H₆N)(μ-H)] (1) with various alkynes are described. Cluster 1 readily reacts with the activated alkyne dimethyl acetylenedicarboxylate (dmad) upon mild heating (65-70 °C) to give the adduct [Os₃(CO)₉(μ-C₉H₆N)(μ₃-MeO₂CCCHCO₂Me)] (2). In contrast, a similar reaction of 1 with diphenylacetylene affords previously reported compounds [Os₃(CO)₁₀(μ-η²-C₉H₆N)(μ-H)] (3), [Os₃(CO)₉(μ-C₄Ph₄)] (4) and [Os₃(CO)₈{μ₃-C(C₆H₄)C₃Ph₃}(μ-H)] (5) while with 2-butyne gives only the known compound [Os₃(CO)₇(μ-C₄Me₄)(μ₃-C₂Me₂)] (6). The new cluster 2 has been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis.     

Tris(pentachlorophenyl) gold(III) complexes

By reaction of Tl(C₆Cl₅)₂Cl with Au(C₆Cl₅)(tht) (tht = tetrahydrothiophen) or [N(PPh₃)₂] [Au(C₆- Cl₅)Cl] the gold(III) complexes [Au(C₆Cl₅)₃(tht)] or [N(PPh₃)₂][Au(C₆Cl₅)₃Cl] respectively, can be prepared. They are the first tris(pentachlorophenyl)- gold(III) complexes to be reported. The ready displacement of tht by other neutral or anionic ligands leads to the synthesis of Au(C₆Cl₅)₃(Ph₂PCH₂PPh₂) or Q[Au(C₆Cl₅)₃X] (Q=N(PPh₃)₂, PPh₃Me or PPh₂Me₂; X=C₆F₅, SCN, Br or I).     

Addition compounds of bis(trifluoromethyl)mercury with tetraphenylphosphonium and tetraphenylarsonium halides and thiocyanates

Addition compounds of Hg(CF₃)₂ with [Ph₄P]X and [Ph₄As]X in the 1:1 ratio for X = Cl, Br, I as well as in the 1:2 ratio for X = SCN, were isolated from aquaeous solution and identified by elemental analysis and infrared spectroscopy. Molar conductance of the thiocyanate compounds in nitrobenzene solution points to its complex-salt nature defined as [Ph₄P]₂[Hg(CF₃)₂(SCN)₂] and [Ph₄As]₂[Hg(CF₃)₂-(SCN)₂], but not for the halide compounds. However, in the monoclinic crystals of the chloride ccompound, as shown by X-ray diffractometry, pairs of [Hg(CF₃)₂ molecules are bridged over by two chlorides in a centro-symmetrical dimer with the CHgC bond angle of 160.5(8)° and the Hg…Cl bond length of 2.823(3) and 2.837(4) Å. The structure was refined to the R factor of 0.053. When X = CN no addition compounds were obtained, the reaction products were HCF₃ and the complex salts [Ph₄P]₂- [Hg(CN)]₄ and [Ph₄As]₂[Hg(CN)]₄, not described so far.     

Synthesis and structural characterization of the mono- and diphosphine-containing diiron propanedithiolate complexes related to [FeFe]-hydrogenases. Biomimetic H2 evolution catalyzed by (mu-PDT)Fe2(CO)4[(Ph2P)2N(n-Pr)

As the new H-cluster models, six diiron propanedithiolate (PDT) complexes with mono- and diphosphine ligands have been prepared and structurally characterized. The monophosphine model complex (μ-PDT)Fe₂(CO)₅[Ph₂PNH(t-Bu)] (1) was prepared by reaction of parent complex (μ-PDT)Fe₂(CO)₆ (A) with 1 equiv of Ph₂PNH(t-Bu) in refluxing xylene, whereas A reacted with 1 equiv of Me₃NO · 2H₂O in MeCN at room temperature followed by 1 equiv of Ph₂PH to give the corresponding monophosphine model complex (μ-PDT)Fe₂(CO)₅(Ph₂PH) (2). Further treatment of 2 with 1 equiv of n-BuLi in THF at −78 °C followed by 1 equiv of CpFe(CO)₂I from −78 °C to room temperature afforded monophosphine model complex (μ-PDT)Fe₂(CO)₅[Ph₂PFe(CO)₂Cp] (3), whereas the diphosphine model complexes (μ-PDT)Fe₂(CO)₄(Ph₂PC₂H₄PPh₂) (4), (μ-PDT)Fe₂(CO)₄[(Ph₂P)₂N(n-Pr)] (5) and (μ-PDT)Fe₂(CO)₄[(Ph₂P)₂N(n-Bu)] (6) were obtained by reactions of A with ca.1 equiv of the corresponding diphosphines in refluxing xylene. All the new model complexes were characterized by elemental analysis, spectroscopy and particularly for 1 and 3-6 by X-ray crystallography. On the basis of electrochemical and spectroelectrochemical studies, model 5 was found to be a catalyst for HOAc proton reduction to H₂, and for this electrocatalytic reaction an ECCE mechanism was proposed.     

Dinuclear Rh(II) complexes with one polypyridyl ligand, structure, properties and antitumor activity

Rhodium(II) complexes [Rh₂(μ-OAc)₂(OAc)(bpy)(H₂O)₂]PF₆ (1), [Rh₂(μ-OAc)₂(OAc)(phen)(H₂O)₂](PF₆)·H₂O (2), [Rh₂(μ-OOCCH₃)₃(OOCCH₃)(phen)] (3) and [Rh₂(μ-O₂CCH₃)₃(O₂CCH₃)(Ph₂phen)] (4) (Ph₂phen = 4,7-diphenyl-1,10-phenanthroline) have been synthesized and characterized by means of NMR, IR and UV-Vis spectroscopic methods. X-ray structure of complex 4·1.5(CH₃COCH₃) has been determined and its geometry and electronic structure has been elucidated using OPBE and B3LYP DFT methods. The compounds are active cytostatic agents against tumor cells.     

Enhancement in anti-tubercular activity of indole based thiosemicarbazones on complexation with copper(I) and silver(I) halides: Structure elucidation,evaluation and molecular modelling

A series of monomeric tetrahedral complexes of stoichiometry, [MX(HL)(Ph₃P)₂] (In case of M = Cu, H¹L, X = I, 1; Br, 2; Cl, 3; H³L, X = I, 4; Br, 5; Cl, 6; H⁴L, X = I, 7; Br, 8; Cl, 9 and in case of M = Ag, H¹L, X = Cl, 13; Br, 14; H²L, X = Cl, 15, Br 16; H³L, X = Cl, 17, Br, 18) were synthesized by the reaction of copper (I) or silver (I) halides with indole-3-thiosemicarbazone (H¹L) or 5-methoxy indole-3-thiosemicarbazone (H²L) or 5-methoxy indole-N¹-methyl-3-thiosemicarbazone (H³L), whereas dimers of stoichiometry, [Cu₂(μ-X)₂(η¹-S-H²L)₂(Ph₃P)₂] (X = I, 10; Br, 11; Cl, 12) were obtained by the reaction of copper (I) halides with indole-N¹-methyl-3-thiosemicarbazone (HIntsc-N¹-Me, H²L). The synthesized complexes were characterized using NMR (¹H and ¹³C) and single crystal X-ray diffraction (H²L, 3, 7, 8, 10, 11 and 13) as well as elemental analysis. Anti- M. tuberculosis activity of ligands (H¹L-H⁴L) and their metal complexes (1–18) were evaluated against M. tuberculosis H37RV strain ATCC 27294. It has been observed that there is unusual enhancement in anti TB activity of these ligands on complexation with copper (I) and silver (I). Molecular modelling studies in the active binding site are also giving complementary theoretical support for the experimental biological data acquired.     

Syntheses, redox and UV-Vis spectroelectrochemical properties of mono- and dinuclear tris(pyrazolyl)borato-oxomolybdenum(IV) complexes with pyridine ligands

Reaction of [Mo^VI(Tp^Me,Me)(O)₂Cl] with a variety of pyridine-based ligands [pyridine (py), 4,4′-bipyridine (bpy), 4-phenylpyridine (phpy) and 1,2′-bis(4-pyridyl)ethene (bpe)] in toluene in the presence of Ph₃P affords the mononuclear oxo-Mo(IV) complexes [Mo(Tp^Me,Me)(O)Cl(L)] (L=py, phpy or monodentate bpy; abbreviated as Mo(py), Mo(phpy) and Mo(bpy), respectively) and the dinuclear complexes [{Mo(Tp^Me,Me)(O)Cl}₂(μ-L)] (L=bpy, bpe; abbreviated as Mo₂(bpy), Mo₂(bpe), respectively). The complex Mo₂(bpy), together with the by-product [{Mo(Tp^Me,Me)(O)Cl}₂(μ-O)], have been crystallographically characterised. Electrochemical studies on the oxo-Mo(IV) complexes reveal the presence of reversible Mo(IV)/Mo(V) couples at around −0.3 V versus ferrocene/ferrocenium in every case. For the dinuclear complexes Mo₂(bpy) and Mo₂(bpe) these redox processes are coincident, indicating that they are largely metal-centred and not significantly delocalised across the bridging ligand. In contrast, Mo₂(bpe) alone shows two reversible reductions, separated by 320 mV; these could be described as ligand-centred reductions of the bpe bridge, or as Mo(IV)/Mo(III) couples which—because of their separation—are substantially delocalised onto the bridging ligand. UV-Vis spectroelectrochemical studies using an OTTLE cell at 243 K revealed that oxidation of the complexes results in spectral changes (collapse of the Mo(IV) d-d transitions, loss in intensity of the Mo→pyridine MLCT transition) consistent with the formation of a Mo(V) state following metal-centred oxidation, but that one-electron reduction of Mo₂(bpe) results in appearance of numerous intense transitions more characteristic of a ligand radical following ligand-centred reduction.     

Syntheses, crystal structures, and characterization of heteronuclear complexes based on a versatile ligand with both acetylacetonate and bis(2-pyridyl) units

A new type of multidentate ligand with both acetylacetonate and bis(2-pyridyl) units on the 1,3-dithiole moiety, 3-[2-(dipyridin-2-yl-methylene)-5-methylsulfanyl-[1,3]dithiol-4-ylsulfanyl]-pentane-2, 4-dione (L), has been prepared. Through reactions of the ligand with Re(CO)₅X (X = Cl, Br), new rhenium(I) tricarbonyl complexes ClRe(CO)₃(L) (2) and BrRe(CO)₃(L) (3), have been obtained. With the use of 2 or 3 as the precursors, the further reactions with (Tp^Ph2)Co(OAc)(Hpz^Ph2) (Tp^Ph2 = hydrotris(3,5-diphenylpyrazol-1-yl)borate); Hpz^Ph2 = 3,5-diphenyl-pyrazole) or M(OAc)₂(M = Mn, Zn), afford four new heteronuclear complexes: ClRe(CO)₃(L)Co(Tp^Ph2) (4), BrRe(CO)₃(L)Co(Tp^Ph2) (5), [ClRe(CO)₃(L)]₂Mn(CH₃OH)₂ (6) and [ClRe(CO)₃(L)]₂Zn(CH₃OH)₂ (7), respectively. Crystal structures of complexes 2 and 4-7 have been determined by X-ray diffraction. Their absorption spectra, photoluminescence and magnetic properties have been studied.     

Reactions of 1,8-bis(diphenylphosphino)naphthalene with ruthenium cluster carbonyls: C-H and C-P bond cleavage reactions

Reactions between Ru₃(CO)₁₂ and 1,8-bis(diphenylphosphino)naphthalene (dppn) have given the four complexes Ru₃(μ-H){μ₃-PPh₂(nap)PPh(C₆H₄)}(CO)₈ (1), Ru₄(μ-H){μ₃-PPh₂(nap)PPh(C₆H₄)}(μ-CO)₃(CO)₇ (2) and Ru₄(μ-H)(μ₃-C₆H₄){μ-PPh(nap)PPh₂}(CO)₁₁ (3) (in refluxing thf), and Ru₄{μ₄-P(nap)PPh₂}(μ₄-C₆H₄)(μ-CO)(CO)₉ (4) (in refluxing toluene) which have been characterised by single crystal X-ray studies. They have been formed by aryl C-H and aryl C-P bond cleavage reactions, presumably from an initial (unobserved) chelate dppn complex. The unchanged chelating ligand is found in Ru₃(μ-dppm)(CO)₈(dppn) (5), obtained from Ru₃(μ-dppm)(CO)₁₀ and dppn in refluxing thf.     

Synthesis and characterisation of the halogenated azanonaboranes [(PrNH2)B8H10XNHPr] (X=Cl, Br, I) and their unexpected hydrolysis to hypho-[B5H10(μ-NHPr)]

Treatment of [(ⁱPrNH₂)B₈H₁₁NHⁱPr] with elemental halogen affords the 8-exo-halogen-substituted derivatives [(ⁱPrNH₂)B₈H₁₀XNHⁱPr] (X=Cl, Br, I). The structures of all three compounds are confirmed by NMR spectroscopy and mass spectrometry, and (for X=Br) by an X-ray diffraction study. The bromoazanonaborane undergoes hydrolytic decomposition to the new five-vertex compound [B₅H₁₀(μ-NHⁱPr)] of hypho-type structure.     

Synthesis, protonation and electrochemical properties of trinuclear NiFe2 complexes Fe2(CO)6(μ3-S)2[Ni(Ph2PCH2)2NR] (R = n-Bu, Ph) with an internal pendant nitrogen base as a proton relay

Two trinuclear NiFe₂ complexes Fe₂(CO)₆(μ₃-S)₂[Ni(Ph₂PCH₂)₂NR] (R = n-Bu, 1; Ph, 2) containing an internal base were prepared as biomimetic models for the active sites of FeFe and NiFe hydrogenases. Treatment of complex Fe₂(CO)₆(μ₃-S)₂[Ni(Ph₂PCH₂)₂N(n-Bu)] (1) with HOTf gave an N-protonated complex [Fe₂(CO)₆(μ₃-S)₂{Ni(Ph₂PCH₂)₂NH(n-Bu)}][OTf] ([1H][OTf]). The structures of complexes 1, 2 and [1H][OTf] were determined by X-ray crystallography, which shows that the proton held by the N atom of [1H][OTf] lies in an equatorial position. Cyclic voltammograms of complexes 1 and [1H][OTf] were studied and compared with that of Fe₂(CO)₆(μ₃-S)₂[Ni(dppe)].     

The synthesis and characterisation of some MnLnX2 complexes (n = 1, L = pyridine, 4-pyrrolidinopyridine,X = Cl,Br, I,NCS; n = 1, L = EtOH,X = Cl,Br; n = 2, L = EtOH,X = I,NCS)

Mono-ligand complexes MnLX₂ (L = pyridine, 4-pyrrolidinopyridine, X = Cl, Br, I, NCS) have been prepared. The pyridine complexes contain only bridging halide and pseudohalide groups, whereas the 4-py complexes contain both bridging and terminal bound anions. Ethanol is coordinated in Mn(EtOH)X₂ (X=C1, Br) and Mn(EtOH)₂X₂ (X=I, NCS). Although the MnLX₂ complexes have the same stoichiometry as the Mn(PR₃)X₂complexes none show any activity towaxds binding dioxygen either in the solid state or in solution.