Search

Redox-Active Bimetallic Complexes and Redox-Responsive Macrocycles

The Transfermium Working Group (TWG) was set up in 1986 under the joint auspices of the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP). Its conclusions, duly endorsed by IUPAC and IUPAP, were published in the following three reports: 1. Criteria that must be satisfied for the discovery of a new chemical element to be recognized, Pure & Appl. Chem., 63, 879-886 (1991). 2. Discovery of the transfermium elements: Introduction to the discovery profiles, Pure & Appl. Chem., 65, 1757-1763 (1993). 3, Discovery of the transfermium elements: Discovery profiles of the transfermium elements, Pure & Appl. Chem., 65, 1764-1814 (1993). IUPAC went a stage further by inviting responses on reports 2 and 3 from the three major groups concerned, i.e., Lawrence Berkeley Laboratory, California; Joint Institute for Nuclear Research, Dubna; and Gesellschaft fur Schwerionenforschung , Darmstadt. These responses together with the TWG's reply to the responses were published unedited in Pure & Appl. Chem., Vol. 65, (1993), pp. 1815-1824.

1: General Aims, Functions and Methods of Chemical Nomenclature 1.1: Introduction 1.2: History of chemical nomenclature 1.3: Aims of chemical nomenclature 1.4: Functions of chemical nomenclature 1.5: Methods of inorganic nomenclature 1.6: Changes to previous IUPAC recommendations 1.7: Nomenclature recommendations in other areas of chemistry 1.8: References 2: Grammar 2.1: Introduction 2.2: Enclosing marks 2.3:Hyphens, plus and minus signs, 'em' dashes and bond indicators 2.4: Solidus 2.5: Dots, colons, commas and semicolons 2.6: Spaces 2.7: Elisions 2.8: Numerals 2.9: Italic letters 2.10: Greek alphabet 2.11: Asterisks 2.12: Primes 2.13: Multiplicative prefixes 2.14: Locants 2.15: Ordering principles 2.16: Final remarks 2.17: References 3: Elements 3.1: Names and symbols of atoms 3.2: Indication of mass, charge and atomic number using indexes (subscripts and superscripts) 3.3: Isotopes 3.4: Elements (or elementary substances) 3.5: Elements in the periodic table 3.6: References 4: Formulae 4.1: Introduction 4.2: Definitions of types of formula 4.3: Indication of ionic charge 4.4: Sequence of citation of symbols in formulae 4.5: Isotopically modified compounds 4.6: Optional modifiers of formulae 4.7: References 5: Compositional Nomenclature, and Overview of Names of Ions and Radicals 5.1: Introduction 5.2: Stoichiometric names of elements and binary compounds 5.3: Names of ions and radicals 5.4: Generalized stoichiometric names 5.5: Names of (formal) addition compounds 5.6: Summary 5.7: References 6: Parenthydride Names and Substitutive Nomenclature 6.1: Introduction 6.2: Parent hydride names 6.3: Substitutive names of derivatives of parent hydrides 6.4: Names of ions and radicals derived from parent hydrides 6.5: References 7: Additive Nomenclature 7.1: Introduction 7.2: Mononuclear entities 7.3: Polynuclear entities 7.4: Inorganic chains and rings 7.5: References 8: Inorganic Acids and Derivatives 8.1: Introduction and overview 8.2: General principles for systematic naming of acids 8.3: Additive names 8.4: Hydrogen names 8.5: Abbreviated hydrogen names for certain anions 8.6: Functional replacement names for derivatives of oxoacids 8.7: References 9: Coordination Compounds 9.1: Introduction 9.2: Describing the constitution of coordination compounds 9.3: Describing the configuration of coordination entities 9.4: Final remarks 9.5: References 10: Organometallic Compounds 10.1: Introduction 10.2: Nomenclature of organometallic compounds of the transition elements 10.3: Nomenclature of organometallic compounds of the main group elements 10.4: Ordering of central atoms in polynuclear organometallic Compounds 10.5: References 11: Solids 11.1: Introduction 11.2: Names of solid phases 11.3: Chemical composition 11.4: Point defect (Kroeger-Vink) notation 11.5: Phase nomenclature 11.6: Non-stoichiometric phases 11.7: Polymorphism 11.8: Final remarks 11.9: References Tables Table I: Names, symbols and atomic numbers of the elements Table II: Temporary names and symbols for elements of atomic number greater Than 111 Table III: Suffixes and endings Table IV: Multiplicative prefixes Table V: Geometrical and structural affixes Table VI: Element sequence Table VII: Ligand abbreviations Table VIII: Structural formulae of selected ligands Table IX: Names of homoatomic, binary and certain other simple molecules, ions, compounds, radicals and substituent groups Table X: Anion names, 'a' terms used in substitutive nomenclature and 'y' terms used in chains and rings nomenclature

An approach is described to the design of potential molecular wires and switches by exploitation of results obtained in the study of non-linear optical properties of hetero- and homo-bimetallic based on combinations of ferrocenyl and metal nitrosyl fragments linked by polarisable bridges.

The 16-electron six-coordinate nitrosyls[M(NO)L*XY], where M = Mo or W, L* = tris(3,5-dimethylpyrazolyl)borate; X, Y = halide, alkoxide, aryloxide, alkyl or arylamide, thiolate) undergo one-electron reduction whose potential is influenced by M, X and Y, and by the substituents attached to X and Y. These species have been incorporated into cyclic polyethers, their reduction potential being sensitive to added alkali metals. The electronegative {M(NO)L*Cl} may be incorporated into dipolar polarisable molecules capable of exhibiting, as solids, strong non-linear optical effects, and they may also be attached to the periphery of porphyrins, causing efficient charge-separation.

A review of the reactions of nitric oxide coordinated to transition metals, and of interest in air pollution control, organo-nitorgen compound synthesis (from nitric oxide, by using transition metal catalysts), and theoretical studies of differences between CO and NO binding to metals, examines the three principal bonding modes in nitrosyl complexes (all metal-to-nitrogen interactions) which involve terminal linear M-N-O groups, terminal bent M-N-O groups (the applicability of the 18-electron rule), and bridging NO groups and covers nucleophilic attack (the nitroprusside ion, reactions of other nitrosyl complexes with nucleophiles); electrophilic attack (the protonation of NO, oxygenation, other O-atom transfer reactions, and formation of N-C bonds); reduction (one-electron and multi-electron processes, and heterogeneous reduction of NO); homogeneous disproportionation of NO (reaction of coordinated NO with nitric oxide, reactions of NO with CO catalyzed by metal complexes); and other reactions, including NO insertion reactions.

Reaction of [(π-C5H5)Mo(NO)X2]2(X = Br or I) with RSH (R = Me, Et, Pr, Bui, Bu, or CH2Ph) gave [(π-C5H5)Mo(NO)(X)(SR)]2 and reduction of this (X = Br) with zinc dust (X = Br) afforded [(π-C5H5)Mo(NO)SR]2. The oxidation of the last with Cl2 or Br2 is briefly discussed. Treatment of [(π-C5H5)Mo(NO)X2]2 with NaSBun(X = Br) gave [(π-C5)Mo(NO)(SPrn)2]2 and with NaSPri(X = I) both [(π-C5H5)Mo(NO)(SPri)]2 and [(π-C5H5)Mo(NO)(SPri)2]2. The mass, n.m.r., i.r., and electronic spectra of the compounds are described.

The reactions between [{(π-C5H5)Mo(NO)I2}2] and disodium cis-dicyanoethylene-dithiolate, disodium tetrachlorobenzene-1,2-dithiolate, toluene-3,4-dithiol, and bis(trifluoromethyl) dithieten proceed in stages. A variety of complexes, of the type [(π-C5H5)Mo(NO)–(S–S)]2, [(π-C5H5)Mo(NO)(I)–(S–S)],–[(π-C5H5)Mo–(S–S)]2-, and [Mo–(S–S)3]2–, where S–S represents the bidentate dithiolato-ligand, have been isolated. With disodium dicyanoethylene-2,2-dithiolate and NaS2CNR2(R = Me or Et), only [(π-C5H5)Mo(NO)(I)S2C:C(CN)2]– and [(π-C5H5)Mo(NO)(I)S2CNR2], respectively, were isolated; the proton magnetic resonance spectra of the latter indicated that the molybdenum atom was an asymmetric centre and that there was considerable multiple-bond character in the S2C–NR2 link. Treatment of [{(π-C5H5)Mo(NO)S2C2(CN)2}2] in solution with triphenyl phosphite afforded [(π-C5H5)Mo(NO){P(OPh)3}S2C2(CN)2]. A voltammetric examination of the complexes revealed that all species, except the dimers, could be oxidised in a one-electron step, but only [Mo(S2C6Cl4)3]– was synthesised.

The stoicheiometric reaction of [(π-C5H5)Mo(NO)(CO)2] with chlorine or bromine affords [(π-C5H5)Mo(NO)X2]2(X = Cl or Br). Those species react with Lewis bases L (L = PPh3, AsPh3, PMe2Ph, pyridine, or bipyridyl) or halide ion (X = Cl or Br) giving [(π-C5H5)Mo(NO)X2L], [(π-C5H5)Mo(NO)Br(PMe2Ph)2]Br, [(π-C5H5)Mo(NO)Cl(bipy)]Cl and [(π- C5H5)Mo(NO)X3]–. The spectral properties of these compounds are compared with those of the corresponding iodides. The synthesis of [(π-C5H5)Mo(NO)(CN)Br]n is briefly reported.

The syntheses of monocationic complexes, [(π-C-H4R)Mn(NO)L2]+, [(π-C5H4R)Mn(NO)LL′]+, and [(π-C5H4R)-Mn(NO)(N–N)]+[R = H or Me, L =γ-picoline, PMe2Ph, PPh3, or P(OPh)3, L = CO and L′= P(OPh)3 or PPh3, or L =γ-picoline and L′= P(OPh)3 or PPh3, and where N–N =α,α′-bipyridyl, o-phenanthroline, or N-(2-pyridylmethylene)-p-toluidine] by reaction of [(π-C5H4R)Mn(NO)(CO)2][PF6] with these ligands is described. The reactions with α-picoline, and the use of triethylamine as a catalyst in the formation of the phosphine complexes, are reported. Treatment of [(π-C5H4R)Mn(NO)(CO)2]+ with triethylamine in acetone in the absence of other ligands gives [(π-C5H4R)Mn(NO)(CO)]2.

The syntheses and chemistry of the related binuclear complexes, [(π-C5H5)Mo(NO)X2]2, [(π-C5H5)Mo(NO)X]2, and [(π-C5H5)Mo(NO)(I)(SCH2Ph)]2(X = I, SCH2Ph or SPh) are reported. Examination of the complexes by mass spectral and i.r. techniques has shown that although the structures of [(π-C5H5)Mo(NO)X2]2 and [(π-C5H5)Mo(NO)(I)(SCH2Ph)]2 appear to be similar and to contain, probably, two bridging groups X, and two terminal X and NO groups, [(π-C5H5)Mo(NO)X]2 may contain only bridging groups, X and NO, and a Mo–Mo bond. The mixed ligand species, [(π-C5H5)Mo(NO)(I)(SCH2Ph)]2, is shown spectrally to exist as isomers, one of which contains bridging SCH2Ph groups and terminal I atoms.

The syntheses of the neutral complexes, [(π-C5H5)Mo(NO)I2L](L = PMe2Ph, AsMe2Ph, AsPh3 or p-MeOC6H4NC), and of monocationic species [(π-C5H5)Mo(NO)I2L]+I–(L = PMe2Ph), by the reaction of the appropriate Lewis base with [{(π-C5H5)Mo(NO)I2}2], is described. From conductance measurements in acetone and dimethyl sulphoxide (Me2SO) it is considered that (π-C5H5)Mo(NO)IL(S)]+(S = Me2CO or Me2SO) and [(π-C5H5)Mo(NO)L(Me2SO)2]2+ are formed in these solvents. The 1H n.m.r. spectra of all the complexes, in a variety of solvents have been interpreted in terms of the solvated species mentioned above, and the form of the methyl proton resonances obtained from the spectra of the species containing PMe2Ph and AsMe2Ph show that these solvated species exist as isomers.

The syntheses and characterisation of the thioxanthate complexes, [(π-C5H5)Mn(NO){S2CSR}](R = But, Bus, Bun, Pri, or Prn), and of the binuclear mercaptide complexes. [(π-C5H5)Mn(NO)SR]2z(z= 0 or + 1; R = But, Bus, or Pri), are described. The former group are shown, by voltammetry, to undergo a reversible one-electron oxidation, and the latter group can be oxidised in two one-electron steps. The Lewis base complexes, [(π-C5H5)Mn(NO)LL′]+[L = L′= CO, P(OPh)3, PPh3, PMe2Ph, 4-methylpyridine, bipyridyl, etc.], also undergo a one-electron voltammetric oxidation process. These new voltammetric data are compared with those previously obtained from related 1,2-dithiolene, 1,1-dithiolene, and dithiocarbamate complexes, and it is shown that the E1/2 values can be correlated with the charge on the complex, and with the N–O stretching frequency. The data indicate that the {(π-C5H5)Mn(NO)} group is significantly responsible for the redox behaviour of the complexes.

The displacement of π-C5H5 rings from [(π-C5H5)2TiCl2], [(π-C5H5)Mo(NO)I2]2, [(π-C5H5)Mn(NO)(CO)2]-[PF6], [(π-C5H5)Fe(NO)]2, and [π-C5H5Ni(CO)]2, by the dithiolato-ligands {S2C2(CN)2}2–, {S2C6Cl4}2– or {S2C6H3Me}2–, and by {S2C·NMe2}–, is discussed. Reaction of [(π-C5H5)2TiCl2] with one, two, or three moles of {S2C6Cl4}2– gave [(π-C5H5)2TiS2C6Cl4], [(π-C5H5)Ti(S2C6Cl4)2]– and [Ti(S2C6Cl4)3]2–, respectively. Treatment of [(π-C5H5)Mn(NO)(CO)2][PF6] with K2S2C6Cl4, in the presence of potassium chloride in ethanol, afforded [Mn(NO)(S2C6Cl4)2]2–, and evidence for [Mn(NO)(S2C6H3Me)2]2– and [Mn(NO){S2C2(CN)2}{S2C6Cl4}]2– is presented; [Mn(NO){S2C2(CN)2}2]2– was obtained by treating manganese(II) chloride with nitric oxide and {S2C2(CN)2}2– or by reaction of [Mn{S2C2(CN)2}2]2– with nitric oxide. The NO stretching frequencies of these new manganese nitrosyl dithiolenes are briefly discussed.The known compounds [Fe(NO){S2C2(C·N)2}2]2– and [Fe(NO)(S2C·NMe2)2] were prepared by reaction of [(π-C5H5)Fe(NO)]2 with Na2S2C2(CN)2 and NaS2C·NMe2, respectively, and [Ni{S2C2(CN)2}2]2– was obtained directly from [(π-C5H5)Ni(CO)]2 and {S2C2(CN)2}2–.

The syntheses of the 1,1-dithiolene complexes, [(π-C5H5)Mn(NO)S2C:X]–, [X = C(CN)·CO2Et, C(CN)·CO·NH2 and N·CN], and of [(π-C5H5)Mn(NO)S2C·NR2](R = Me or Et) are described. Both series of complexes undergo one-electron oxidation reactions which were detected voltammetrically, and the half-wave potentials were dependent on the nature of the sulphur ligand substituents. The NO stretching frequencies of the compounds were also dependent on the sulphur ligand substituents and on the overall charge on the complex. The existence of [(π-C5H5)Mn(NO)S2C·X]0 and of [(π-C5H5)Mn(NO)S2C·NR2]+ was confirmed by e.s.r. spectral studies and the g-tensors and ΔaMn‡ were significantly different from those obtained from the 1,2-dithiolene analogues, [(π-C5H5)Mn(NO)S2C2R2]0 and [Mn(π-C5H5)(NO)S2C6Cl4]0.