Publisher Summary The chemistry of metal–alkynyl compounds is developing at a rapid pace. The bonds of alkynyl ligands, like those of organic alkynes have been shown to participate in a rich set of chemical transformations. Electronic-absorption band maxima and extinction coefficients have been reported for a large number of metal–alkynyl complexes. Casual comparisons of electronic-absorption band energies or intensities among a series of compounds in the absence of such experiments are not without the risk of misinterpretation because a variety of important effects not associated with the presence or absence of M-CCR π-bonding may be operative such as mixings between electronic states of identical symmetry but different orbital character. The best and simplest means of placing the M–C bond distances of metal–alkyl complexes in a context that allows insight into whether or not they manifest M-CCR π-interactions is to compare them to M–C bond distances of complexes where such effects are expected to be insignificant, as for metal–alkynyl compounds.

The Bonding of Metal-Alkynyl Complexes

Bacteria carrying plasmids with the mer operon, which encodes the proteins responsible for the bacterial mercury detoxification system, have the ability to transport Hg(II) across the cell membrane...

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Structures of the Reduced and Mercury-Bound Forms of MerP, the Periplasmic Protein from the Bacterial Mercury Detoxification System†,‡

The (1)H NMR solution structure of the Cu(I)-bound form of Atx1, a 73-amino acid metallochaperone protein from the yeast Saccharomyces cerevisiae, has been determined. Ninety percent of the (1)H and 95% of the (15)N resonances were assigned, and 1184 meaningful NOEs and 42 (3)J(HNH)(alpha) and 60 (1)J(HN) residual dipolar couplings provided a family of structures with rmsd values to the mean structure of 0.37 +/- 0.07 A for the backbone and 0.83 +/- 0.08 A for all heavy atoms. The structure is constituted by four antiparallel beta strands and two alpha helices in a betaalphabetabetaalphabeta fold. Following EXAFS data [Pufahl, R., Singer, C. P., Peariso, K. L., Lin, S.-J., Schmidt, P. J., Fahrni, C. J., Cizewski Culotta, V., Penner-Hahn, J. E., and O'Halloran, T. V. (1997) Science 278, 853-856], a copper ion can be placed between two sulfur atoms of Cys15 and Cys18. The structure of the reduced apo form has also been determined with similar resolution using 1252 meaningful NOEs (rmsd values for the family to the mean structure are 0.67 +/- 0.12 A for the backbone and 1.00 +/- 0.12 A for all heavy atoms). Comparison of the Cu(I) and apo conformations of the protein reveals that the Cu(I) binding cysteines move from a buried site in the bound metal form to a solvent-exposed conformation on the surface of the protein after copper release. Furthermore, copper release leads to a less helical character in the metal binding site. Comparison with the Hg(II)-Atx1 solid-state structure [Rosenzweig, A. C., Huffman, D. L., Hou, M. Y., Wernimont, A. K., Pufahl, R. A., and O'Halloran, T. V. (1999) Structure 7, 605-617] provides insights into the copper transfer mechanism, and a pivotal role for Lys65 in the metal capture and release process is proposed.

Solution structure of the Cu(I) and apo forms of the yeast metallochaperone, Atx1.

Structural insights have been provided by mercury-199 nuclear magnetic resonance (NMR) into the metal receptor site of the MerR metalloregulatory protein alone and in a complex with the regulatory target, DNA. The one- and two-dimensional NMR data are consistent with a trigonal planar Hg-thiolate coordination environment consisting only of Cys side chains and resolve structural aspects of both metal ion recognition and the allosteric mechanism. These studies establish 199Hg NMR techniques as useful probes of the metal coordination environment of regulatory proteins, copper enzymes, and zinc transcription factor complexes as large as 50 kilodaltons.

https://science.sciencemag.org/content/sci/268/5209/380.full.pdf

Mercury-199 NMR of the metal receptor site in MerR and its protein-DNA complex.

Publisher Summary This chapter focuses on supracyclopentadienyl derivatives in organometallic chemistry. Within organometallic chemistry—synthetic, analytical, physical, applied, and theoretical chemists are involved in research projects, dealing with highly substituted cyclopentadienylide (Cp)-metal complexes. Supra-Cp's are a major focus of this chapter, whereas for many others they are just a sideline where the bulkiness is a minor feature in the comparative study of certain phenomena. This chapter reveals unifying interest, sometimes with no cross-referencing to similar bulky Cp systems or even different metals carrying the same supra-Cp. The basic bulky Cp systems that are common in organometallic chemistry are discussed in the chapter, in their anionic form as ball-and-stick models with the hydrogens included. Other basic bulky Cp's described in the chapter are di(isobutyl)(tert-buty1)-Cp, penta(isopenty1)- Cp [isopentyl=( H,C2)2CH-], and tris(methoxycarbony1)-Cp. This chapter presents highly substituted Cp's, supracyclopentadienes that so far have escaped attention as ligands in organometallic complexes: tetra(terfbuty1)- Cp, 3,Mimethyl- and 3,5di-n-propyl- 1,2,4-triphenyl-Cp, and 1,2,3,5-tetraphenyl-4-p(7-cycloheptatrienyl)phenyl-Cp. Most of the bulky ring substituents are simple hydrocarbon moities, either alkyl or aryl groups, and consequently the supra-Cp's can be divided into two classes: peralkyl and peraryl systems. The use of bulky cyclopentadienes with functional group substituents causes problems in organometallic synthesis. Although there is a sizable number of Cp- metal complexes with only one functional group on the Carbon, ring examples for persubstituted systems are limited. This chapter also covers tetrasubstituted fulvalenes ethylene-bridged bis(tetrahydroindeny1) complexes and a dibornacyclopentadienyl ligand.

Bulky or Supracyclopentadienyl Derivatives in Organometallic Chemistry

Application de la RMN du 95Mo a l'etude d'organo-complexes carbonyles du molybdene

Réactions d'insertion du cyanoacétylène et du dicyanoacétylène dans les deux liaisons métalhydrogène des dihydrures [(C5H5)2MH2] (M Mo ou W)

Transition metal-cyanocarbon chemistry: IX. Reactions of monocyanoacetylene with dicarbonylcyclopentadienylmethylthiolatoiron(II). Crystal structures of [FeC(O)C(CN)CH(SCH3) (η5-C5H5)(CO)] and of μ-η2-Fe(CCCN)(η5-C5H5)(CO)2][Co(CO)3]2

Complexes biscyclopentadienyles avec des liaisons metal de transitionmercure

Transition metal-cyanocarbon chemistry X. Reactions of monocyanoacetylene and dicyanoacetylene with organometallic compounds of cobalt(I) and nickel(II). Crystal structure of [Co(CCCN)2(η5-C5H5)(P(C6H5)3)]☆

M.M. Kubicki

Papers

Application de la RMN du 95Mo a l'etude d'organo-complexes carbonyles du molybdene

Réactions d'insertion du cyanoacétylène et du dicyanoacétylène dans les deux liaisons métalhydrogène des dihydrures [(C5H5)2MH2] (M Mo ou W)

Transition metal-cyanocarbon chemistry: IX. Reactions of monocyanoacetylene with dicarbonylcyclopentadienylmethylthiolatoiron(II). Crystal structures of [FeC(O)C(CN)CH(SCH3) (η5-C5H5)(CO)] and of μ-η2-Fe(CCCN)(η5-C5H5)(CO)2][Co(CO)3]2

Complexes biscyclopentadienyles avec des liaisons metal de transitionmercure

Transition metal-cyanocarbon chemistry X. Reactions of monocyanoacetylene and dicyanoacetylene with organometallic compounds of cobalt(I) and nickel(II). Crystal structure of [Co(CCCN)2(η5-C5H5)(P(C6H5)3)]☆