Cyanide Ligands Research Articles

Coordination chemistry of macrocyclic multidentate Lewis acids. Synthesis and structures of complexes of cyclic trimeric perfluoro-o-phenylenemercury with N,N-dimethylacetamide and n-butyronitrile

Cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 readily reacts with N,N-dimethylacetamide and n-butyronitrile to form the complexes {[(o-C6F4Hg)3](MeCONMe2)2} and {[(o-C6F4Hg)3](PrnCN)}, respectively. According to X-ray diffraction data, the amide ligands are located above and below the plane of the macrocycle, each being coordinated to all Hg atoms of the macrocycle through the O atom. The nitrile ligand is bound to the macrocycle through the N atom, all Hg atoms being also involved in this bonding.

Redox Potential - (Electronic) Structure Relationships in 18- and 17-Electron Mononitrile (or Monocarbonyl) Diphosphine Complexes of Re and Fe

The organonitrile or carbonyl complexes cis-[ReCl(RCN)(dppe)2] (1) (R = 4-Et2NC6H4 (1a), 4-MeOC6H4 (1b), 4-MeC6H4 (1c), C6H5 (1d), 4-FC6H4 (1e), 4-ClC6H4 (1f), 4-O2NC6H4 (1g), 4-ClC6H4CH2 (1h), t-Bu (1i); dppe = Ph2PCH2CH2PPh2), or cis-[ReCl(CO)(dppe)2] (2), as well as trans-[FeBr(RCN)(depe)2]BF4 (3) (R = 4-MeOC6H4 (3a), 4-MeC6H4 (3b), C6H5 (3c), 4-FC6H4 (3d), 4-O2NC6H4 (3e), Me (3f), Et (3g), 4-MeOC6H4CH2 (3h); depe = Et2PCH2CH2PEt2), novel trans-[FeBr(CO)(depe)2]BF4 (4) and trans-[FeBr2(depe)2] (5) undergo, as revealed by cyclic voltammetry at a Pt-electrode and in aprotic non-aqueous medium, two consecutive reversible or partly reversible one-electron oxidations assigned as ReI → ReII → ReIII or FeII → FeIII → FeIV. The corresponding values of the oxidation potentials IE1/2ox and IIE1/2ox (waves I and II, respectively) correlate with the Pickett's and Lever's electrochemical ligand and metal site parameters. This allows to estimate these parameters for the various nitrile ligands, depe and binding sites (for the first time for a FeIII/IV couple). The electrochemical ligand parameter show dependence on the "electron-richness" of the metal centre. The values of IE1/2ox for the ReI complexes provide some supporting for a curved overall relationship with the sum of Lever's electrochemical ligand parameter. The Pickett parametrization for closed-shell complexes is extended now also to 17-electron complexes, i.e. with the 15-electron ReII and FeIII centres in cis-{[ReCl(dppe)2]}+ and trans-{FeBr(depe)2}2+, respectively.

EXAFS Study of the Structure of Desolvated Cluster Compounds of Re and Mo with Cyanide and Thiocyanate Ligands

This paper reports on EXAFS and XANES studies of structural changes in complex compounds (H3O)2Co3[Re6Se8(CN)6]2⋅14.5H2O, Cs2Co[Re6S8(CN)6]⋅2H2O, and Co(DMF)6[Mo6Br8(NCS)6] containing the octahedral cluster anions of rhenium [Re6X8(CN)6]4– (X = S, Se) or molybdenum [Mo6Br8(NCS)6]2–, induced by vacuum annealing at temperatures of up to 250°C. According to EXAFS and XANES data, the complex cluster anions do not undergo any pronounced changes during annealing. The parameters of the local environment of the cobalt cations have been determined. Structural models of the environment of the cations in various compounds after desolvation have been constructed. For Co(DMF)6[Mo6Br8(NCS)6], vacuum annealing at 250°C leads to a complete removal of DMF and formation of a new compound, Co[Mo6Br8(NCS)6], in which the cobalt atoms are coordinated by four sulfur atoms of the SCN groups.

Synthesis and Structure of Co2[Re6Se8(CN)6]⋅12H2O

The cluster anions [Re6X8(CN)6] 4− were synthesized not long ago [1-4]. Anions of this kind have six terminal cyano groups. These are topological analogs of hexacyanometallate anions [M(CN)6] n−, reacting with transition metal cations to form polymer compounds. The larger size of cluster anions compared to mononuclear ones lead to unusual structures containing large cavities [5-7]. Another interesting feature of large cluster anions is possible stabilization of oligomer cations. For example, interaction of aqueous solutions of [Cu(H2O)6] 2+ with a solution of the tetranuclear anion cyano complex [Re4Te4(CN)12] 4− leads to formation of [Cu4(OH)4][Re4Te4(CN)12] containing a hydroxo cation tetramer [Cu4(OH)4] 4+ [8]. Here we report on the synthesis and structural study of Co2[Re6Se8(CN)6]⋅12H2O containing cobalt cation dimers bridged by water molecules. Experimental. Co2[Re6Se8(CN)6]⋅12H2O (1) was prepared by diffusion of the starting substances in silica gel. For this, Na2SiO3⋅9H2O (12.25 g) was dissolved in H2O (50 ml) and titrated to pH 7 while vigorously stirring with 1 M hydrochloric acid (∼20 ml). The resulting mixture was poured into a U-tube and allowed to stay for 1-2 days until the gel completely polymerized. An aqueous solution containing K4[Re6Se8(CN)6] [2] was applied to the gel in one knee of the U-tube, and an aqueous solution of CoCl2 was applied in the other knee. After 4 weeks, well-faceted orange prisms crystallized in the middle part of the tube. The structure of compound 1 was established by X-ray diffraction analysis. A yellowish orange prismatic single crystal sized 0.08×0.05×0.05 mm was chosen from the gel. The data were collected at 293 K on a Rigaku AFC5R diffractometer with a rotating anode (MoKα radiation, graphite monochromator). Crystal data: Co2Re6Se8C6N6O12H24, mol. wt. 2749.50, monoclinic, with cell parameters a = 9.875(4), b = 16.375(2), c = 12.1875(30) A, β = 96.00(2)°, Vcell = 1959.96(90) A3, space group P21/c, Z = 4, ρcalc = 3.753 g/cm 3. The number of reflections collected was 6280 (2θmax = 60.06°), including 5972 unique reflections (Rint = 0.09). An absorption correction (μ = 26.45 cm –1) was applied using the DIFABS program [9]. The structure was solved by direct methods with SHELX-86. The full-matrix least-squares refinement was carried out anisotropically for Re, Co, and Se atoms with teXsan program package [10]. The water hydrogen atoms were not located. The final R indices were R = 0.0708, wR = 0.0989 for 3692 reflections with I ≥ 2σ(I). Atomic coordinates are given in Table 1; bond lengths, in Table 2. Discussion of results. The structure of [Re6Se8(CN)6] 4− in compound 1 is shown in Fig. 1. The interatomic distances and the anion geometry are analogous to those found for other compounds with octahedral cluster anions [Re6X8(CN)6] 4− [1-7]. While dimerization via the bridging water molecules is not typical for transition metal cations [11], centrosymmetric dimers of Co2+ cations bridged by two water molecules are formed in 1 (Fig. 2). The distances from the bridging oxygen atom to the cobalt atoms are nonequivalent (2.14 and 2.25 A). This leads to a distortion of the Co2O2 rhomb to a parallelogram. The Co–Co distance is 3.43 A, ruling out the presence of a metal—metal bond. Cobalt has a slightly distorted octahedral environment formed by three water molecules (two bridging O2, O2a and one terminal O1) and three nitrogen atoms of the cyanide ligands belonging to three different anions. For the CoO3N3 coordination unit, edge and face geometrical isomers are possible. In this structure, the face isomer is realized (Fig. 2). The Co–N distance is 2.05-2.09 A; this value is typical for the Co2+–N coordination bond.

Complexation of cyclic trimeric perfluoro- o-phenylenemercury with nitriles. A remarkable sensitivity of the composition and structure of the resulting complexes to the nature of a nitrile

Cyclic trimeric perfluoro- o-phenylenemercury ( o-C 6F 4Hg) 3 ( I) is capable of reacting with nitriles to form complexes whose composition and structure are dramatically dependent on the nature of the nitrile used. In the case of acrylonitrile, the complex, [( o-C 6F 4Hg) 3(CH 2CHCN)], containing one nitrile molecule per one molecule of I is produced. According to an X-ray structure analysis, the acrylonitrile ligand in this complex is bonded to all Hg atoms of the cycle through the nitrogen atom. The reaction of I with acetonitrile gives complex [( o-C 6F 4Hg) 3(MeCN) 2] which contains two nitrile ligand per one molecule of the macrocycle. This complex has a shape of a spinning top the equatorial girdle of which is the mercury-containing metallacycle, whilst the axis direction is fixed by the linear MeCN ligands located above and below the metallacycle plane. Finally, the isolated complex of I with benzonitrile, [( o-C 6F 4Hg) 3(PhCN) 3], contains three molecules of the coordinated nitrile per one macrocycle molecule. A remarkable structural feature of this complex is that here all the nitrile ligands are located on one side of the metallacycle plane and, in addition, differ from each other in the geometry of coordination with the Hg atoms.

High-Nuclearity Metal-Cyanide Clusters: Assembly of a Cr8Ni6(CN)24 Cage with a Face-Centered Cubic Geometry

The synthesis of high-nuclearity metal-cyanide clusters presents a possible means of controlling magnetic properties in the design of new single-molecule magnets. Previous work employed tridentate blocking ligands in directing the assembly of a cubic [(tacn)8Co8(CN)12]12+ (tacn = 1,4,7-triazacyclononane) cluster; an improved crystal structure now confirms the lack of a guest water molecule inside the cluster cage. The ability to generate larger clusters by using a blocking ligand on only one of the mononuclear reaction components is demonstrated with the synthesis of a fourteen-metal [(Me3tacn)8Cr8Ni6(CN)24]12+ cluster. The geometry of this cluster consists of a cube of eight Me3tacn-ligated CrIII ions connected via bridging cyanide ligands to six square-planar NiII ions situated just above the center of each cube face. Surprisingly, no guest species are evident within the 284 Å3 cavity defined by the rigid metal-cyanide cage. Assembly of the cluster in boiling aqueous solution involves a linkage isomerization wherein the carbon end of each cyanide ligand reorients from binding a CrIII center in the reactant to binding the softer NiII center in the product. Consequently, the NiII ions become diamagnetic, resulting in magnetic behavior at high temperatures that is consistent with eight isolated CrIII (S = 3/2) ions per cluster. However, below 30 K, a drop in the χMT is attributed to weak antiferromagnetic coupling between CrIII ions through the LUMO orbitals of the [Ni(CN)4]2--like units centering each cluster face. Carrying out the assembly reaction in methanol at −40 °C forestalls the linkage isomerization, yielding a high-spin green form of the cluster. Reaction of [(Me3tacn)8Cr8Ni6(CN)24]12+ with [Ni(CN)4]2- affords an aggregate species with a tetracyanonickelate ion capping each face of the cluster through a mean Ni···Ni contact of 3.00(1) Å, an interaction that destroys the long-range antiferromagnetic coupling between CrIII ions. Efforts to construct a larger cluster with an edge-bridged cubic geometry produced a linear [(Me3tacn)2(cyclam)NiCr2(CN)6]2+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) fragment exhibiting an S = 4 ground state. The weak ferromagnetic coupling (J = 10.9 cm-1) within this cluster leads to a more rapid decrease in the magnetization with increasing temperature at higher magnetic fields as a result of the Zeeman splitting and population of low-lying excited states.

Polymerization of tert-butylacetylene by seven-coordinate heterobimetallic tungsten(II) and molybdenum(II) compounds

The reaction of tert-butylacetylene ( t-BA) in the presence of seven-coordinate tungsten(II) and molybdenum(II) compounds [MCl(M′Cl 3)(CO) 3(NCR) 2] (M=Mo, W; M′=Sn, Ge; R=Me, Et) leads to the catalytic coupling of t-BA molecules and the formation of high-molecular-weight ( M̄ n>10 5) soluble polymers. The geometric structure of poly( tert-butylacetylene) (P- t-BA) was determined by means of 1H- and 13C-NMR spectroscopy. The monitoring of the reaction between t-BA and the metal complex by means of 1H-NMR spectroscopy provided further insight into the initiation step of this polymerization process. The reaction of a heterobimetallic compound with a stoichiometric amount of t-BA yields compounds in which CO and/or nitrile ligands have been replaced by a t-BA ligand. The alkyne molybdenum(II) and tungsten(II) complexes formed were characterized structurally by means of IR and NMR spectroscopy. The possible mechanisms for the formation of very reactive intermediate compounds and their role in the catalytic process are discussed.

M(mu-CN)Fe(mu-CN)M' chains with phthalocyanine iron centers: redox, spin-state, and mixed-valence properties.

Dinuclear complexes with M-CN-ZnPc and M-CN-FePc-CN arrays and trinuclear complexes with M(mu-CN)Fe(mu-CN)M' arrays containing central metal phthalocyaninato (Pc) and external Cp(dppe)Fe or Cp(PPh3)2Ru building blocks (M) and having all possible orientations of the bridging cyanide ligands were subjected to electrochemical and preparative redox reactions. The species with unpaired electrons show characteristic MMCT bands in the near-IR spectra, the energies of which depend in a typical fashion on the nature of the building blocks and the orientation of the cyanide bridges and can be correlated with the redox potentials. Cyclic voltammetry has revealed electronic communication between the external organometallic units. An analysis of the MMCT spectra allows the assignment of the odd-electron complexes as class II mixed-valence species. The magnetic moments of the complexes with central Fe(III)Pc units are characteristically higher than the spin-only value for one unpaired electron. A Mössbauer investigation has shown that the M-CN-Fe(III)Pc-NC-M complexes undergo a low-spin-to-high-spin crossover of the Fe(III) component above room temperature.

Coordination Compounds of tripodCoII and tripodCoI − Selective Substitution and Redox Behaviour

The five-coordinate tripodCobalt(II) compound [tripodCoIICl2] (2) [tripod = CH3C(CH2PPh2)3] undergoes selective substitution of its chlorine groups on activation with KPF6 in the first substitution step and by TlPF6 in the second. Compounds of the type [tripodCoIILL′]2+ with two nitrile (32+) or isonitrile (52+) ligands are obtained by this route. Compounds [tripodCoIIL2] containing two equal ligands L are also accessible from CoIIaq as the starting material. The syntheses of [tripodCoII(CNR)2]2+ (52+) and [tripodCoIIX2] (X = CN, NCO, NCS) (6) are reported. Different routes to tripodCoI derivatives are described. Depending on the nature of the co-ligands, four-coordinate − [tripodCoINCO] (7) − or five-coordinate − [tripodCoI(CNR)2]+ (5+) − compounds are obtained. Several high-yield syntheses of [tripodCoI-alkyne]+ (8+) compounds are reported. The compounds are characterised by the usual analytical and spectroscopic techniques including X-ray analysis of selected examples.

Vanadium Complexes of the N(CH2CH2S)33-and O(CH2CH2S)22-Ligands with Coligands Relevant to Nitrogen Fixation Processes

Vanadium(III) and vanadium(V) complexes derived from the tris(2-thiolatoethyl)amine ligand [(NS3)3-] and the bis(2-thiolatoethyl)ether ligand [(OS2)2-] have been synthesized with the aim of investigating the potential of these vanadium sites to bind dinitrogen and activate its reduction. Evidence is presented for the transient existence of (V(NS3)(N2)V(NS3), and a series of mononuclear complexes containing hydrazine, hydrazide, imide, ammine, organic cyanide, and isocyanide ligands has been prepared and the chemistry of these complexes investigated. [V(NS3)O] (1) reacts with an excess of N2H4 to give, probably via the intermediates (V(NS3)(NNH2) (2a) and (V(NS3)(N2)V(NS3) (3), the V(III) adduct [V(NS3)(N2H4)] (4). If 1 is treated with 0.5 mol of N2H4, 0.5 mol of N2 is evolved and green, insoluble [(V(NS3))n] (5) results. Compound 4 is converted by disproportionation to [V(NS3)(NH3)] (6), but 4 does not act as a catalyst for disproportionation of N2H4 nor does it act as a catalyst for its reduction by Zn/HOC6H3Pri2-2,6. Compound 1 reacts with NR1(2)NR2(2) (R1 = H or SiMe3; R2(2) = Me2, MePh, or HPh) to give the hydrazide complexes [V(NS3)(NNR2(2)] (R2(2) = Me2, 2b; R2(2) = MePh, 2c; R2(2) = HPh, 2d), which are not protonated by anhydrous HBr nor are they reduced by Zn/HOC6H3Pri2-2,6. Compound 2b can also be prepared by reaction of [V(NNMe2)(dipp)3] (dipp = OC6H3Pri2-2,6) with NS3H3. N2H4 is displaced quantitatively from 4 by anions to give the salts [NR3(4)][V(NS3)X] (X = Cl, R3 = Et, 7a; X = Cl, R3 = Ph, 7b; X = Br, R3 = Et, 7c; X = N3, R3 = Bu(n), 7d; X = N3, R3 = Et, 7e; X = CN, R3 = Et, 7f). Compound 6 loses NH3 thermally to give 5, which can also be prepared from [VCl3(THF)3] and NS3H3/LiBun. Displacement of NH3 from 6 by ligands L gives the adducts [V(NS3)(L)] (L = MeCN, nu CN 2264 cm-1, 8a; L = ButNC, nu NC 2173 cm-1, 8b; L = C6H11NC, nu NC 2173 cm-1, 8c). Reaction of 4 with N3SiMe3 gives [V(NS3)(NSiMe3)] (9), which is converted to [V(NS3)(NH)] (10) by hydrolysis and to [V(NS3)(NCPh3)] (11) by reaction with ClCPh3. Compound 10 is converted into 1 by [NMe4]OH and to [V(NS3)NLi(THF)2] (12) by LiNPri in THF. A further range of imido complexes [V(NS3)(NR4)] (R4 = C6H4Y-4 where Y = H (13a), OMe (13b), Me (13c), Cl (13d), Br (13e), NO2 (13f); R4 = C6H4Y-3, where Y = OMe (13g); Cl (13h); R4 = C6H3Y2-3,4, where Y = Me (13i); Cl (13j); R4 = C6H11 (13k)) has been prepared by reaction of 1 with R4NCO. The precursor complex [V(OS2)O(dipp)] (14) [OS2(2-) = O(CH2CH2S)2(2-)] has been prepared from [VO(OPri)3], Hdipp, and OS2H2. It reacts with NH2NMe2 to give [V(OS2)(NNMe2)(dipp)] (15) and with N3SiMe3 to give [V(OS2)(NSiMe3)(dipp)] (16). A second oxide precursor, formulated as [V(OS2)1.5O] (17), has also been obtained, and it reacts with SiMe3NHNMe2 to give [V(OS2)(NNMe2)(OSiMe3)] (18). The X-ray crystal structures of the complexes 2b, 2c, 4, 6, 7a, 8a, 9, 10, 13d, 14, 15, 16, and 18 have been determined, and the 51V NMR and other spectroscopic parameters of the complexes are discussed in terms of electronic effects.

Coordination Compounds oftripodCoII andtripodCoI − Selective Substitution and Redox Behaviour

The five-coordinate tripodCobalt(II) compound [tripodCoIICl2] (2) [tripod = CH3C(CH2PPh2)3] undergoes selective substitution of its chlorine groups on activation with KPF6 in the first substitution step and by TlPF6 in the second. Compounds of the type [tripodCoIILL′]2+ with two nitrile (32+) or isonitrile (52+) ligands are obtained by this route. Compounds [tripodCoIIL2] containing two equal ligands L are also accessible from CoIIaq as the starting material. The syntheses of [tripodCoII(CNR)2]2+ (52+) and [tripodCoIIX2] (X = CN, NCO, NCS) (6) are reported. Different routes to tripodCoI derivatives are described. Depending on the nature of the co-ligands, four-coordinate − [tripodCoINCO] (7) − or five-coordinate − [tripodCoI(CNR)2]+ (5+) − compounds are obtained. Several high-yield syntheses of [tripodCoI-alkyne]+ (8+) compounds are reported. The compounds are characterised by the usual analytical and spectroscopic techniques including X-ray analysis of selected examples.

Dirhenium(II) complexes containing monodentate and polydentate nitrile ligands

The complex Re 2Cl 4(μ-dppa) 2 (dppa=Ph 2PNHPPh 2) has been reacted with EtCN and PhCN to afford the complexes [Re 2Cl 3(μ-dppa) 2(NCR) 2]PF 6 (R=Et or Ph), [Re 2Cl 3(μ-HN 2C 2Et 2)(μ-dppa) 2(NCEt)]Cl and [Re 2Cl 3(μ-HN 2C 2Et 2)(μ-dppa) 2(NCEt)](PF 6) 2 which are derivatives of the [Re 2] 4+, [Re 2] 5+ and [Re 2] 6+ cores, respectively. This behaviour is similar to the reactions of Re 2Cl 4(μ-dppm) 2 (dppm=Ph 2PCH 2PPh 2) with monodentate nitriles. The reactions of Re 2Cl 4(μ-dppm) 2 with the polydentate nitrile ligands 1,4-dicyanobenzene (1,4-DCB), 1,4-dicyanobut-2-ene (1,4-DCBE) and tris(2-cyanoethyl)phosphine (CEP) also give complexes of this same type in which the nitrile ligand utilizes only one of its CN groups. This is confirmed by an X-ray crystal structure determination of [Re 2Cl 3(μ-dppm) 2(1,4-DCB) 2]PF 6, in which the ReRe bond is retained (Re–Re distance 2.2637(12) Å) and the 1,4-DCB ligands are monodentate.

Obtaining ligand geometries from paramagnetic shifts in low-spin haem proteins.

Previously, the theoretical relationship between paramagnetic chemical shifts and the axial ligands in low-spin haem proteins has been tested extensively in haems b and c with His, Met, and cyanide ligands. Variations in the electronic structure of the haem and the magnetic susceptibility tensors have been shown to depend primarily on the axial ligand geometry, and the shifts of haem substituents have been used to obtain the first structural information for several cytochromes. Recently, the database of assigned spectra for bis-His haems has been extended sufficiently for an empirical equation to be produced for treating 1H NMR data from haem methyl groups at 298 K. However, the database used contains large systematic deviations and the form of the equation leads to systematic errors in the ligand geometries. This article describes the link with the semi-empirical methods used previously and provides a set of corrected empirical parameters as well as an improved equation. The possibilities for generalising the empirical method to account for ligands other than His and temperatures other than 298 K are discussed.

Simple Quaternary Ammonium Ions R4N+ (R=nPr, nBu, nPen) as Versatile Structure Directors for the Synthesis of Zeolite-Like, Heterobimetallic Cyanide Frameworks

The preparation of three new examples of water insoluble host/guest assemblies of the general composition: [(R4N)(Me3Sn)2M(CN)6·zH2O] (R=n-propyl or n-pentyl, M=Fe or Co, 0≤z≤2) from likewise polymeric super-Prussian-blue derivatives [(Me3Sn)3M(CN)6] and aqueous (R4N)X solutions are reported. According to combined single-crystal X-ray (3a and 3a*: R=nPr, M=Co, z=2; 5b: R=nPen, M=Fe, z=0.5), powder X-ray diffraction (XRD), and multinuclear (13C, 15N, 59Co, 119Sn) CPMAS solid-state magnetic resonance studies, 3a and 3a* contain cis- and trans-isomeric [Co(CN)4(CNSnMe3OH2)2]− building blocks, respectively, which are held together exclusively by Sn←OH2···NC–Co hydrogen bonds. In striking contrast, the building blocks of 5b and 5a are infinite [M–CN–Sn–NC] chains. In all these assemblies, also significant C–H···NC hydrogen bonds between the encapsulated R4N+ guest ion and exclusively terminal cyanide ligands of the host seem to play a notable auxiliary role.

Synthesis of nitrile ligands bearing tricarbonyl (η 6-arene)chromium complexes and conjugated spacers

The synthesis of nitrile ligands linked to tricarbonyl (η 6-arene)chromium complexes by conjugated spacers is performed by reacting aromatic bromo nitrile derivatives with tricarbonylchromium-complexed phenylacetylene using Sonogashira coupling reaction.

Controlling substitution chemistry in ruthenium(II) systems. Synthesis of heteroleptic complexes incorporating the [Ru([9]aneS3)]2+ metal center.

The complex [Ru(py)3([9]aneS3)][PF6]2, 1 (py = pyridine), has proved to be a suitable starting material for the synthesis of heteroleptic Ru(II) complexes. By exploiting unfavorable steric interactions between 2-H and 6-H hydrogens of coordinated pyridyl ligands, we have synthesized half-sandwich complexes incorporating the thiocrown [9]aneS3 and a variety of facially coordinated N-donor ligands. Such complexes are easily prepared: Stirring 1 at room temperature in the presence of a suitable nitrile ligand leads to the exclusive substitution of one py ligand to produce complexes such as [([9]aneS3)Ru(py)2(NCMe)][PF6]2, 2. However, if the same reaction is carried out at higher temperatures, two py ligands are substituted, leading to complexes such as [([9]aneS3)Ru(py)(NCMe)2][PF6]2, 3. An alternative approach to such heteroleptic species has also been developed which exploits the restricted ability of thioethers to neutralize positive charges through sigma-donation. This phenomenon allows the synthesis of heteroleptic complexes in a two-step procedure via monocationic species. By variation of the donor/acceptor properties of ligands incorporated into the [Ru([9]aneS3)]2+ metal center, it is possible to tune the Ru(III)/Ru(II) redox couple over a range of > 700 mV. The solid-state structures of 1-3 were confirmed by X-ray crystallography studies. Crystal data: C22H30F12N4O2P2RuS3 (1.CH3NO2), monoclinic, Cc, a = 23.267(5) A, b = 11.5457(18) A, c = 26.192(5) A, alpha = 90 degrees, beta = 114.836(10) degrees, gamma = 90 degrees, Z = 8; C18H25F12N3P2RuS3 (2), triclinic, P1, a = 11.3958(19) A, b = 11.4280(19) A, c = 11.930(2) A, alpha = 100.518(3) degrees, beta = 100.542(3) degrees, gamma = 112,493(3) degrees, Z = 2; C15H23F12N3P2RuS3 (3), orthorhombic, Pna2(1)), a = 14.748(5) A, b = 18.037(18) A, c = 10.341(5) A, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, Z = 4.

Spectroelectrochemical studies on some new ruthenium(II) complexes containing both cyanide and isocyanide ligands

New ruthenium(II) complexes trans, trans, trans-[RuCl2(NCR)2(CNR′)2] (R=Me or Ph, R′=But, xylyl or cyclohexyl (cy)) have been prepared by treating mer-[RuCl3(NCR)3] with the appropriate isocyanide ligand CNR′ in EtOH/CH2Cl2. These complexes have been shown to be oxidisable electrochemically in situ to the analogous ruthenium(III) species trans, trans, trans-[RuCl2(NCR)2(CNR′)2]+ in 0.5 mol dm−3 [NBun4][PF6]/CH2Cl2 solution, the stereochemistry of the oxidised species being established by use of an infrared spectroelectrochemical (IRRAS) technique. The electronic absorption spectra of the ruthenium(III) species obtained by use of an OTTLE cell are also reported and discussed.

Transition metal promoted cyclization reactions of nitrile ligands: Stereochemically controlled synthesis and structural investigation of some chiral oxazoline platinum(II) complexes

The reactions of the nitrile complexes cis- and trans-[PtCl2(NCR)2] with S(+)-2-chloro-1-propanol in the presence of 2 equiv. of n-BuLi afford the chiral oxazoline complexes cis- and trans-[PtCl2{(R)-N=C(R)OCH2CH(Me)}2] [cis, R=Me (1), cis, R=Ph (2); trans, R=Ph (3)]. The structures of 1 and 2 were determined by X-ray analysis which allowed to establish the R configuration of the oxazoline rings. The reactions of cis- and trans-[PtCl2(NCR)2] with S(+)-2-chloro-1-phenylethanol and R(−)-2-chloro-1-phenylethanol in the presence of 2 equiv. of n-BuLi afford the oxazoline complexes cis- and trans-[PtCl2{(S)-N=C(R)OCH(Ph)CH2}2] [cis, R=Me (4), cis, R=Ph (5); trans, R=Ph (6)] and cis- and trans-[PtCl2{(R)-N=C(R)OCH(Ph)CH2}2] [cis, R=Me (7), trans, R=Me (8); trans, R=Ph (9)]. The structure of 6 was determined by an X-ray investigation which allowed to establish the S configuration of the oxazoline rings. The proposed mechanism for the nitrile to chiral oxazoline conversion entails nucleophilic attack of the alkoxide, generated by deprotonation reaction of the corresponding alcohol with n-BuLi, followed by intramolecular cyclization. This latter step proceeds with complete inversion of configuration at the chiral carbon atom for 1–3, while with retention of configuration for 4–9.

Structural characterisation of [Pt(NH 3) 4] 2[W(CN) 8][NO 3]·2H 2O donor–acceptor complex

The bimetallic [Pt(NH 3) 4] 2[W(CN) 8][NO 3]·2H 2O is characterised by single-crystal X-ray diffraction [S.G. P2 1/ m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) A ̊ , Z=2]. All platinum centres have the square-plane D 4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D 4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1) ∗ separations of 4.77(2), 4.55(2) ∗ and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO 3 − between parallel [Pt(1)(NH 3) 4] 2+ planes and the second consists of [W(CN) 8] 3− interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH 3) 4] 2+. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH 3 ligands, water molecules and oxygen atoms of NO 3 − counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer.

Mono and Dinuclear Tungsten Alkenyl-Carbyne Complexes Bridged by Cyanide and Diisocyanide Ligands: Synthesis, Electrochemical- and 183W-NMR Studies

Mono and Dinuclear Tungsten Alkenyl-Carbyne Complexes Bridged by Cyanide and Diisocyanide Ligands: Synthesis, Electrochemical- and 183W-NMR Studies