Dalton Trans Research Articles

Accurate Redeterminations of 1,1'-Dibenzoylferrocene and (4-Nitrophenyl)ferrocene

In the solid state, molecules of 1,1′-dibenzoylferrocene, [Fe(C12H9O)2], (I), are linked to form infinite chains in the [100] direction via (cyclopentadienyl)C—H⋯O hydrogen bonds [C⋯O 3.354 (4) Å]. In the structure of (4-nitrophenyl)ferrocene, [Fe(C5H5)(C11H8NO2)], (II), there are no C—H⋯O hydrogen bonds and molecules are separated by normal van der Waals distances. For earlier determinations see Struchkov [Dokl. Akad. Nauk SSSR (1956), 110, 67–70] for (I) and Roberts et al. [J. Chem. Soc. Dalton Trans. (1988), pp. 1549–1556] for (II).

Solid-State NMR and X-ray Diffraction Studies of the Geometry and Intramolecular Dynamics of Bis(organothiophosphoryl) Dichalcogenides

Information stored in the Cambridge Crystallographic Data Centre shows that anti−anti conformation is common for bis(organothiophosphoryl) dichalcogenides. In view of the 1−4 repulsion, the syn−syn conformation of the S1P−X−X4−PS (X = S and Se) backbone is unfavorable. However, in compounds with at least one phenyl group directly bonded to the phosphorus, such as bis[tert-butyl(phenyl)thiophosphinyl] disulfide (Knopik, P. et al. J. Chem. Soc., Dalton Trans. 1993, 2749), bis(diphenylthiophosphinyl) disulfide (Gallacher, A. C. et al. Acta Crystallogr. 1993, C49, 1793) and bis[tert-butyl(phenyl)thiophosphinyl] diselenide (this work) there is the syn−syn geometry caused by the aromatic−aromatic interactions. Bis[tert-butyl(phenyl)thiophosphinyl] diselenide is monoclinic, space group C2/c with a = 20.424(2) Å, b = 9.373(1) Å, c = 12.907(1) Å, V = 2406.4(2) Å3, Dc = 1.525 (2) g/cm3, and Z = 4. Refinement using 2351 reflections for 118 variables gives R = 0.047. We have used high-resolution 77Se MAS NMR to study the structural properties of the compound. The principal elements Tii of the 77Se effective dipolar/chemical shift tensor were calculated from the intensities of the spinning sidebands. The values of the anisotropy and asymmetry parameters reflect the distortion of the environment of selenium. For a series of bis(organothiophosphoryl) diselenides the T33 tensor component gives the largest contribution to the isotropic chemical shifts and the span parameter Ω reflects the strength of the diselenide bond. Molecular packing significantly influences the intramolecular dynamics of the aliphatic and aromatic groups. The 13C dipolar dephasing experiment and line shape analysis of the 1H−2H CP/MAS spectra of selectively 2H-labeled compounds show that the phenyl groups are static as a result of the aromatic−aromatic interaction, while the tert-butyl groups are under a fast motional regime, with C3v jumps around the P−C and C−C bonds.

Electronic structure and molecular dynamics of Na2Li

Following the first report (Mile, B., Sillman, P. D., Yacob, A. R. and Howard, J. A., 1996, J. chem. Soc. Dalton Trans, 653) of the EPR spectrum of the mixed alkali-metal trimer Na2Li a detailed study has been made of the electronic structure and structural dynamics of this species. Two isomeric forms have been found: one of the type, Na–Li–Na, of C2v, symmetry and another, Li–Na–Na, of Cs symmetry. Also, there are two linear saddle points which correspond to ‘inversion’ transition structures, and a saddle point of C s symmetry which connects the two minima. A molecular dynamics investigation of these species shows that, at the temperature of the reported experiments (170 K), the C2v minimum is not 'static', but undergoes quite rapid inversion. At higher temperatures the C minimum converts to the Cs form, but by a mechanism very different from that suggested by minimum energy path considerations.

Electronic structure and molecular dynamics of Na2Li

Following the first report (Mile, B., Sillman, P. D., Yacob, A. R. and Howard, J. A., 1996, J. chem. Soc. Dalton Trans, 653) of the EPR spectrum of the mixed alkali-metal trimer Na2Li a detailed study has been made of the electronic structure and structural dynamics of this species. Two isomeric forms have been found: one of the type, Na–Li–Na, of C2v, symmetry and another, Li–Na–Na, of Cs symmetry. Also, there are two linear saddle points which correspond to ‘inversion’ transition structures, and a saddle point of C s symmetry which connects the two minima. A molecular dynamics investigation of these species shows that, at the temperature of the reported experiments (170 K), the C2v minimum is not 'static', but undergoes quite rapid inversion. At higher temperatures the C minimum converts to the Cs form, but by a mechanism very different from that suggested by minimum energy path considerations.

Extent of Intramolecular Aromatic-Ring Stacking in Ternary Cu(2+) Complexes Formed by 2,2'-Bipyridyl or 1,10-Phenanthroline and Flavin Mononucleotide (FMN(2)(-))(1)(,)(2).

The stability constants of the 1:1 complexes formed between Cu(Arm)(2+), where Arm = 2,2'-bipyridyl or 1,10-phenanthroline, and flavin mononucleotide (= FMN(2)(-) = riboflavin 5'-phosphate) were determined by potentiometric pH titrations in aqueous solution at 25 degrees C and I = 0.1 M (NaNO(3)). The experimental conditions were carefully selected such that only the monomeric complex species formed. On the basis of previously established log K versus pK(a) straight-line plots (Chen, D.; et al. J. Chem. Soc., Dalton Trans. 1993, 1537-1546) for the corresponding ternary complexes of simple phosphate monoesters and phosphonate derivatives, R-PO(3)(2)(-), where R is a noncoordinating residue, it is shown that the stability of the ternary Cu(Bpy)(FMN) and Cu(Phen)(FMN) complexes is considerably higher than is expected on the basis of the basicity of the phosphate group of FMN(2)(-). By comparison with the stability of the ternary Cu(Arm)(G1P) complexes, where G1P = glycerol 1-phosphate, which had previously been studied (Liang, G.; et al. J. Am. Chem. Soc.1992, 114, 7780-7785) and in which the coordination sphere of Cu(2+) is identical with the one in Cu(Arm)(FMN), it can unequivocally be shown that the mentioned enhanced stability of the Cu(Arm)(FMN) complexes is solely due to the formation of intramolecular stacks; their formation degree reaches for Cu(Bpy)(FMN) and Cu(Phen)(FMN) about 80 and 90%, respectively. These, as well as recent results regarding the self-stacking of FMN(2)(-) (Bastian, M.; Sigel, H. Biophys. Chem. in press) show that the flavin moiety is ideally suited for stacking and charge-transfer interactions, which are so important for the flavin coenzymes in nature.

Ternary complexes in solution 1 with hydrogen phosphate and methyl phosphate as ligands

The stability constants of the 1:1 complexes formed between Cu(Arm) 2+, where Arm = 2,2′-bipyridyl or 1,10-phenanthroline, and methyl phosphate, CH 3OPO 3 2−, or hydrogen phosphate, HOPO 3 2−, were determined by potentiometric pH titration in aqueous solution (25°C; l = 0.1 M, NaNO 3). On the basis of previously established log K versus p K a straight-line plots (D. Chen et al., J. Chem. Soc., Dalton Trans. (1993) 1537–1546) for the complexes of simple phosphate monoesters and phosphonate derivatives, R-PO 3 2−, where R is a non-coordinating residue, it is shown that the stabilities of the Cu(Arm) (CH 3OPO 3) complexes are solely determined by the basicity of the -PO 3 2− residue. In contrast, the Cu(Arm) (HOPO 3) complexes are slightly more stable (on average by 0.15 log unit) than expected on the basicity of HPO 4 2−; this is possibly due to a more effective solvation including hydrogen bonding, an interaction not possible with coordinated CH 3OPO 3 2− species. Regarding biological systems the observation that HOPO 3 2− is somewhat favored over R-PO 3 2− species in metal ion interactions is meaningful.

Platinum metal complexes of secondary phosphines: Synthesis and NMR spectroscopic studies of [M(PCy 2H) 3Cl] +, M = Pt, Pd

Reaction of MCl 2 (M = Pd, Pt) with PCy 2H in EtOH under dinitrogen yielded the unusual tris-secondary phosphine complexes [MCl(PCy 2H) 3]X (X − = Cl −, BF − 4, PF − 6) in high yield as stable products. Retention of the secondary phosphine protons in these complexes has been confirmed by 1H, 31P and 195Pt NMR spectroscopic studies. These results confirm that the PH bond in coordinated PCy 2H is stronger than in coordinated PPh 2H. Similar reaction of NiCl 2 · 6H 2O with PCy 2H yields the bis-secondary phosphine complex [NiCl 2(PCy 2H) 2] as reported previously (R. A. Palmer, H. F. Giles and D. R. Whitcomb, J. Chem. Soc., Dalton Trans. 1978, 1671 ; R. A. Palmer and D. R. Whitcombe, J. Mag. Res. 1980, 39, 371). Variable temperature 31P NMR spectroscopy confirms that the cis isomer exists exclusively in CH 2Cl 2 solution, while the trans isomer is the dominant form in benzene solution. Addition of excess PCy 2H leads to species with higher phosphine : metal ratios at low temperature as seen by 31P NMR spectroscopy and FAB mass spectrometry.

A new phase of bis[2-(diphenylphosphino-κP)phenylazanido-κN](ethanolato)(oxo)rhenium(V)

The title compound, [Re(C 18 H 15 NP) 2 (C 2 H 5 O)O], was synthesized by the oxidation-substitution reaction of [Re III (PNH) 2 (PNH 2 )]Cl, where PNH 2 is 2-(diphenylphosphino)phenylamine, with NEt 3 in EtOH. The X-ray diffraction study of this new triclinic phase, designated β, confirms the molecular structural details for the monoclinic α isomer, which crystallized in space group P2 1 /c with a=12.056 (3), b=26.303 (6), c=11.005 (3) A, β=102.32 (2) o [Refosco, Tisato, Bandoli, Bolzati, Dolmella, Moresco & Nicolini (1993). J. Chem. Soc. Dalton Trans. pp. 605-618]

The dimolybdenum pentapivalate anion: X-ray crystal structure and dynamic solution behaviour and comments on the substitutional lability of containing compounds

The reaction between Mo 2(O 2CBu t) 4 and [Bu n 4N] +[Bu tCO 2] − in toluene yields the yellow toluene-soluble salt [Bu n 4N] +[Mo 2(O 2CBu t) 5] − as large yellow plates upon crystallization. The molecular struture of the anion contains the now common paddle-wheel or lantern M 2(O 2C) 4 core, ▪ = 2.1035(7) and MoO = 2.12(2) Å (av), with a monodentate pivalate ligand coordinated to one metal atom, MoO = 2.298(5) Å in the axial position and MoMoO (η l-pivalate) = 176.6(1)°. In CD 2Cl 2 and toluene-d 8 solutions the anion shows fluxional behaviour such that exchange between all pivalates is rapid on the NMR time-scale at room temperature. At −80°C this fluxional process becomes sufficiently slow to lead to the expected 4:1 ratio for the Bu t protons. In pyridine-d 5 the exchange of pivalates is slower but still sufficiently fast to lead to coalescence at elevated temperatures. In pyridine solution the predominant species are Mo 2(O 2CBu t) 4(py) 2 and [Bu n 4N] +[Bu tCO 2] −. These findings complement earlier work wherein [Et 4N] +[Mo 2(O 2CCF 3) 5] − was prepared (Garner and Senior, J. Chem. Soc., Dalton Trans. 1975, 1171) and the exchange of CF 3CO − 2 groups in the reaction between Mo 2(O 2CCF 3) 4 and NaO 2CCF 3 in CH 3CN was studied (Sasaki et al., Bull. Chem. Soc. Japan 1979, 52, 446). The facile intramolecular exchange of pivalate ligands in the Mo 2(O 2CBu t) − 5 anion emphasizes that Mo 4+ 2 containing compounds are kinetically labile to associative nucleophilic substitution reactions. Possible reaction pathways leading to exchange of Bu tCO − 2 are discussed.

Sodium Salts of Chlorine Oxyacid Anions, Cl(+7), Perchlorate, XPS Comparison Spectra

High quality sodium perchlorate has been analyzed as one in a series of chlorine-oxy anion sodium salts, Chloride to Perchlorate. The spectra include survey and high resolution scans over the major photopeaks, the sodium Auger transitions and the valence band of the compound. Several references have been listed as additional sources of information of the nature of these materials and previous XPS analyses [see R. Manne, J. Chem. Phys. 46, 4645 (1967); R. G. Copperthwaite, J. Chem. Soc. Dalton Trans. 1977, 1117; R. Prins and T. Navakov, Chem. Phys. Lett. 9, 593 (1971); R. Prins, J. Chem. Phys. 61, 2580 (1974); and F. Solymosi, Structure and Stability of Salts of Halogen Oxyacids in the Solid Phase (Wiley–Interscience, New York, 1977)].

Oxidation of supported and unsupported polymeric μ-fluoro(phthalocyanine) aluminium(III)

The polymeric, fluoro-bridged phthalocyanine complex [Al(Pc)F] n [J.P. Linksy, T.R. Paul, R.A. Nohr and M.E. Kenney, Inorg. Chem., 19 (1980) 3131] has attracted considerable attention since it can be doped using a variety of oxidizing agents to give conducting materials [R.S. Nohr, P.M. Kuznesof, K.J. Wynne, M.E. Kenney and P.G. Sieberman, J. Am. Chem. Soc., 103 (1981) 4371; P. Brant, D.C. Weber, S.G. Haupt, R.S. Nohr and K.J. Wynne, J. Chem. Soc. Dalton Trans. (1985) 269; D. Djurado, A. Hamai and C. Fabre, Synth. Met., 29 (1989) 71F and refs therein]. However, many features of the doping process, particularly structural aspects, remain unclear. Evaporation of [Al(Pc)F] n onto single crystal KCl results in an epitaxial film which has been structurally characterized by high resolution transmission electron microscopy [J.R. Fryer and M.E. Kenney, Macromolecules, 21 (1988) 259]. In the present work oxidation of [Al(PC)F] n supported on KCl or silica wafers had been compared with oxidations performed on polycrystalline material in the presence of MeCN. Oxidizing agents used include hexafluorides (UF 6, MoF 6, WF 6), pentafluorides (AsF 5, PF 5, IF 5) halogens (Cl 2, Br 2, I 2) and the NO + cation. The colour change, blue→purple occurs in all cases. There are spectroscopic similarities between film and polycrystalline reactions and the oxidized products are freely soluble in MeCN. The spectroscopic and TEM data suggest that in many cases oxidation is accompanied by depolymerization. Depolymerization appears to be important also when [Al(Pc)F] n is protonated by CF 3CO 2H and CF 3SO 3H.

Complexation de l'aluminium(III) polymerise et hydrolyse par les ions salicylate. Etude cinetique et thermodynamique

Le polymère Al13 est le constituant majeur de certains coagulant-floculants utilisés dans le traitement des eaux. Nous avons étudié la complexation de ce polymère ainsi que des formes monomériques de l'aluminium par les ions salicylates dont les fonctions acides et le caractère aromatique peuvent constituer un modèle des acides fulviques présents dans les eaux de surface. La stoechiométrie et les constantes d'équilibre des complexes formés ont été déterminées à l'aide de mesures de spectroscopie u.v.-visible. Les monomères forment avec les ions salicylates des complexes 1-1 avec une constante K = 105.02. Avec le polycation Al13, les complexes formés ont une constante de stabilitéK13 > 1020, comprenant 6 molécules de salicylate par Al13. Un modèle cinétique prenant en compte toutes les espèces présentes: Al(OH)(H2O)52+, Al(OH)2(H2O)4+ et Al13O4(OH)247+ rend bien compte des résultats expérimentaux. La combinaison des données cinétiques obtenues avec certains résultats de la littérature concernant la complexation des espèces monomériques a permis la détermination des constantes de vitesse relatives à la complexation de l'ion salicylate avec Al(OH)2(H2O)4+ soit k3 = 2728 M−1 s−1. Avec le polycation Al13 la constante de vitesse est kp = 3679 ±113 M−1 s−1 à 25°C.

Interaction of diiodine with some tetra-substituted dithiooxamides. Crystal and molecular structure of bis(morpholinothiocarbonyl)bis(diiodine)

The reaction of some tetra-substituted dithiooxamides R2NC(S)C(S)NR2 (R = CH3:Me4dto; R = C2H5:Et4dto; R2N = OC4H8N:Mo2dto) with diiodine has been investigated by spectrophotometric methods in CHCl3. The formation in solution of 1:1 and 1:2 charge-transfer (c.t.) complexes between the reagents has been observed. A new computer program, derived from "SUPERQUAD" (P. Gans, A. Sabatini, and A. Vacca. J. Chem. Soc. Dalton Trans. 1195 (1985)), has been applied to evaluate the formation constants. The 1:2 c.t. complexes have been isolated in the solid state, and an X-ray structure analysis of the [OC4H8NC(S)C(S)NC4H8O]•2I2 compound indicated that the crystals are triclinic, space groups [Formula: see text], with a = 14.659(6), b = 15.111(6), c = 9.317(5) Å, α = 92.29(2), β = 99.71(2), γ = 99.48(2)° and Z = 4. In particular the torsion angle S—C—C—S (≈90°) shows that the conformation of the dithiooxamide is not trans.

Plastocyanin conformation: The effect of the oxidation state on the p Ka of nitrotyrosine-83

Plastocyanin treated with tetranitromethane was nitrated at a single location, Tyr-83. Tyr-83 and its neighboring negative charges have been implicated as a binding site for positively charged redox agents (Chapman, S.K., Watson, A.D. and Sykes, A.G. (1983) J. Chem. Soc. Dalton Trans. 1983, 2543–2548). No effect was observed on either the plastocyanin midpoint redox potential or its reaction kinetics with P-700 + and cytochrome f. This makes nitration an ideal spectroscopic probe for monitoring changes in the environment of Tyr-83. The p K a of the nitrotyrosine was 8.6 and 8.3 for reduced and oxidized plastocyanin, respectively, indicating that the charge on the copper atom is ‘felt’ at Tyr-83. The high p K a value for both forms indicates that Tyr-83 is in a negatively charged environment, near residues Nos. 42–45 and Nos. 59–61. The extinction of the nitrotyrosine chromophore at 360 nm was not affected by a change in redox state. However, the ellipticity of this transition was greater for the oxidized form, indicating that environment of Tyr-83 is dependent upon the charge on the copper atom. This suggests an electrostatically driven conformational change at Tyr-83. A conformational change at Tyr-83 could regulate the binding of plastocyanin with its reaction partners in order to promote smooth electron transport.

Co-crystallized bis(hexafluoroacetylacetonato)palladium(II) and 3-cyano-2,2,5,5-tetramethyl-2,5-dihydropyrrolyl-1-oxyl, C10H2F12O4Pd.2C9H13N2O

[Li(CaHloO2)3] [Zr2ClaO(C4H4N)2(C lo H 15)2].C4H 1002 The CsMe 5 ring shows r:-coordination: the Z r - C lengths range from 2.49 (1) to 2.57 (2)A. The bond lengths and angles within the ligands themselves are normal (Bynum, Hunter, Rogers & Atwood, 1980). The two independent L i - O lengths, 2.09 (1) and 2.20 (3) A, have large e.s.d.'s associated with them due to the high thermal motion of the cation. However, the distances are long when compared to the L i - O lengths of 2.064(9) and 2 . 1 1 2 ( 4 ) A found for the five- coordinate Li in [Li(dme)2lBr (Rogers & Atwood, 1983, unpublished results). An uncoordinated dme molecule was found highly disordered about a crystallographic twofold axis. Refinement of the parameters of this moiety could not be carried out, and the non-hydrogen atoms were included with fixed contributions. The rather high R value resulted from this difficulty. We are grateful to the National Science Foundation for support of this work. References BYNUM, R. V., HUNTER, W. E., ROGERS, R. D. & ATWOOD, J. L. (1980). Inorg. Chem. 19, 2368-2374. BYNUM, R. V., ZHANG, H., HUNTER, W. E. & ATWOOD, J. L. (1984). Can. J. Chem. Submitted. CROMER, D. T. & LmERMAN, D. (1970). J. Chem. Phys. 53, CROMER, D. T. & WABER, J. T. (1965). Acta Cryst. 18, 104-109. FACHINETTI, G., FLORIAN1, C., CHIES1-VILLA, A. & GUASTINI, C. (1979),J. Am. Chem. Soc. 101, 1767-1775. HOLTON, J., LAPPERT, M. F., BALLARD, D. G. H., PEARCE, R., ATWOOD, J. L. & HUNTER, W. E. (1979). J. Chem. Soc. Dalton Trans. pp. 45-53. HUNTER, W. E., HRNC1R, D. C., BYNUM, R. V., PENTTILA, R. A. & ATWOOD, J. L. (1983). Organometallics, 2, 750-755. LAPPERT, M. F., RILEY, P. I., YARROW, P. I. W., ATWOOD, J. L., HUNTER, E. W. & ZAWOROTKO, M. J. (1981). J. Chem. Soc. Dalton Trans. pp. 814-821. PETERSEN, J. L. (1979). J. Organomet. Chem. 166, 179-192. SALDARRIAGA-MOLINA, C. H., CLEARFIELD, A. & BERNAL, I. (1974). Inorg. Chem. 13, 2880-2885. WOLCZANSKI, P. T., THRELKEL, R. S. & SANTARSlERO, B. D. (1983). Acta Co'st. C39, 1330-1333. Acta Cryst. (1984). C40, 1814-1817 Co-crystallized Bis(hexafluoroacetylacetonato)palladium(II) and 3-Cyano-2,2,5,5- tetramethyl-2,5-dihydropyrrolyl- l-oxyl, C 10H2F 12 O4Pd.2C9H13 N20 BY LEIGH C. PORTER AND ROBERT J. DOEDENS* Department o f Chemistry, University o f California, Irvine, California 92717, USA (Received 16 April 1984; accepted 28 June 1984) M r=850.9, monoclinic, P2x/n, a = b=19.139(7), c = 1 0 . 9 2 8 ( 3 ) A, f l = v = 1772 (1) A 3, z = 2, Dx= 1.595 Mg m -3, 2(Mo Ka) = 0.71073 A, g = 0.62 mm -l, F ( 0 0 0 ) = 8 5 2 , T = 2 9 6 K , final R = 0 . 0 4 5 for 2498 observed reflections. The co-crystallized species are arranged in alternating layers perpendicular to the b axis, with only van der Waals type interactions between layers. Magnetic susceptibility data (6-300 K) are consistent with the presence of one free spin on each nitroxyl radical. Abstract. I n t r o d u c t i o n . Several complexes in which a transition- metal ion is directly bound to a nitroxyl group have recently been prepared and characterized by crystal structure analyses (Anderson & Kuechler, 1980; Dickman & Doedens, 1983; Porter, Dickman & Doedens, 1983; Dickman, 1983). These molecules constitute a relatively rare example of a series of metal * To whom correspondence should be addressed. complexes containing a coordinated flee-radical ligand which retains its radical character. They also show other interesting features, including unusual metal- ligand binding geometries and various types of mag- netic behavior. One factor which favors formation of a metal-nitroxyl bond is a strongly Lewis acidic metal center. Most frequently this has been achieved by the presence of electron-withdrawing groups on other ligands. The nature of the nitroxyl ligand is also a factor, though this has not been thoroughly investigated. The title compound was prepared in the course of exploratory studies designed to define the conditions under which a transition-metal-nitroxyl bond will be formed. From bis(hexafluoroacetylacetonato)- palladium(II) [Pd(F6acac) 2] and 3-cyano-2,2,5,5-tetra- methyl-2,5-dihydropyrrolyl-1-oxyl (tmpCN) in pentane a compound of stoichiometry Pd(F6acac)2(tmpCN)2 was obtained in good yield. A crystal structure analysis was performed to establish the mode of binding of the tmpCN in this material. © 1984 International Union of Crystallography

The behaviour of copper and thallium hexafluoromolybdates(V) in acetonitrile

Copper(I), copper(II), and thallium(III) hexafluoromolybdates(V), prepared by the oxidation of the metals in acetonitrile with molybdenum hexafluoride (A. Prescott, D.W.A.Sharp, and J.M. Winfield, J. Chem. Soc., Dalton Trans. , 1975, 963) have been investigated by cyclic voltametry. Half wave potentials, E 1 2 V vs. Ag p+/Ag were obtained using a evacuable cell equipped with anexternal Ag p+/Ag electrode, enabling strict anerobic conditions to be maintained. A number of reversible or quasi-reversible electron transfer processes have been observed, enabling comparison with synthetic work to be made. Results for Cu I and Cu II hexafluoromolybdates(V) are in accord with preparative experience. MoF 6. Mo VI/Mo VE 1 2 +1.600V, oxidises Cu metal to Cu II in MeCN, and Cu II is reduced by Cu O to Cu I , Cu lI/Cu IE 1 2 = +0.750 or +0.710V for Cu I and Cu II solutes respectively, Cu I/Cu OE 1 2 = −0.720V not reversible. A wave at E 1 2 = −0.350V is assigned to Mo V/Mo IV by analogy with Ag I hexafluoromolybdate (D.W.A. Sharp, unpublished work). E 1 2 data for I 2 in MeCN, I 2/I 3 - = 0.280, I 3 −/I − = -0.116V, suggest that reduction of MoF 6 − by I is not likely, in contrast to the situation in SO 2 (A.J. Edwards and R.D. Peacock, Chem. Ind. , 1960, 1441). Reduction of MoF 6 − by Cu o in MeCN should be feasible, but appears to be very slow. Pure Tλ III hexafluoromolybdate(V) is obtained from Tλ o and MoF 6 only when the mole ratio MoF 6:Tλ>5:1. Smaller ratios produce yellow solids in which Mo:Tλ is ca . 2:1. Tλ III is a stronger oxidising agent than Cu II in MeCN, as oxidation of Cu I by Tλ III is rapid and quantitative. However a reversible electron transfer wave assignable to Tλ III/Tλ I is not observed in the expected fange +1.600 to +0.710V possibly because of solute-electrode interactions.