Metal−Metal Interactions in Linked Metallocenes

Synthese und Eigenschaften des Bis(pentamethylcyclopentadienyl)germaniums (2) und -zinns (1) sowie der ionischen (Pentamethylcyclopentadienyl)germanium- und -zinn-tetrafluoroborate 4 und 3 werden beschrieben. Die Strukturen von 1 – 4 resultieren aus spektroskopischen und analytischen Daten sowie im Falle von 1 und 3 auch aus Rontgenstrukturanalysen. Elektronenstruktur und Bindungsverhaltnisse in 1 – 4 werden auf der Basis von MO-Modellrechnungen diskutiert.



Bis(pentamethylcyclopentadienyl)germanium and -tin and (Pentamethylcyclopentadienyl)germanium- and -tin Cations: Synthesis, Structure, and Bonding Properties



Synthesis and properties of bis(pentamethylcyclopentadienyl)germanium (2) and -tin (1) and of the ionic (pentamethylcyclopentadienyl)germanium- and -tin tetrafluoroborates 4 and 3 are described. The structures of 1 – 4 result from spectroscopic and analytical data and in the case of 1 and 3 also from X-ray structure analyses. The bonding in 1 – 4 is discussed on the basis of model MO calculations.

Bis(pentamethylcyclopentadienyl)germanium und ‐zinn sowie (Pentamethylcyclopentadienyl)germanium‐ und ‐zinn‐Kationen: Synthese, Struktur und Bindungsverhältnisse

Flexible coordination of indenyl ligands in sandwich complexes of transition metals. Molecular structures of [(η-C9R7)2M] (M = Fe, R = H, Me; M = Co, Ni, R = H): Direct measurement of the degree of slip-fold distortion as a function of d-electron count

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

Metallocenes, substituted metallocenes, and organometallic salts containing metal-carbon bonds have been investigated by electrospray mass spectrometry (ESMS). Organometallic salts yielded stable cations in high abundances; metallocenes appeared in the oxidized form [i.e., as bis(cyclopentadienyl) metal cations, Cp2M+]. Identifications were confirmed by inspection of the natural isotope distribution patterns. ESMS response vs concentration (log-log) plots showed a linear range between 10(-9) and 10(-5) M for both CP2Fe and [Cp2Fe]+[PF6]-. For solutions of equivalent concentration, however, the salt form always yielded a higher abundance of Cp2Fe+. Neutral metallocenes are ionized by an electrochemical oxidation (electron-removal) mechanism at or near the electrospray (ES) capillary (needle). Increasing electrospray appearance potentials for Cp2M+ (M = metal) formation correlated with increasing haff-wave potentials for oxidation [E1/2(OX)] and increasing ionization energies (IE) in the series: decamethylferrocene, 1,1'-dimethylferrocene, ferrocene, formylferrocene, carboxylferrocene, acetylferrocene, 1,1'-discetylferrocene, osmocene, and ruthenocene. For osmocene [relatively high E1/2-(ox) and IE], ESMS conditions were established whereby protonation was competitive with oxidation, thus creating two pathways of ion formation. In methylene chloride solvent, chloride ion was incorporated into the inner sphere of certain metallocenes subjected to ESMS, forming Cp2RuCl+ and Cp2OsCl+ complexes via nucleophilic addition. These latter Ru(IV) and Os(IV) species also formed analogous gas-phase complexes with trifluoroacetate ion and hydroxide ion. Results have been rationalized on the basis of ion stability considerations.

I.R. Lyatifov

Papers

Crystal and molecular structures of two polymethylferrocenes: sym-octamethylferrocene and decamethylferrocene

The 1H and 13C nuclear magnetic resonance and IR adsorption spectra of substituted polymethylferrocenes

sym-polymethylferricinium hexafluorophosphates

The 1H and 13C NMR spectra of sym-methylcobalticinium hexafluorophosphates

Fragmentation of symmetrically substituted methylferrocenes under electron impact