Michael Malaun

IMIDAZOLINE-2-YLIDENE METAL COMPLEXES WITH PENDANT FERROCENYL SUBSTITUENTS

Abstract Imidazolium and benzimidazolium salts with ferrocenylated alkyl side chains are prepared as progenitors of N-[(ferrocenyl)alkyl](benz)imidazoline-2-ylidene carbenes, which form metal complexes of W(0), Pd(II), and Hg(II). X-ray structures and other spectroscopic properties show that these carbene precursors and complexes are analogous to published non-ferrocenylated complexes with regard to the coordination sphere at the metal, but different in terms of steric protection of the central metal by the bulky ferrocenyl substituents and in terms of distinguishable redox potentials of the ferrocene/ferrocenium couple.

N-HETEROCYCLIC CARBENES WITH N-FERROCENYL-N'-METHYL-SUBSTITUTION : SYNTHESIS, REACTIVITY, STRUCTURE AND ELECTROCHEMISTRY

Abstract Benzimidazolium salts with one N -ferrocenyl substituent and with one N -methyl substituent are prepared by a synthetic sequence involving coupling of the metallocenyl group to a non-cyclic orthophenylene-diamine precursor, ring closure, and oxidation. From these carbene progenitors a range of carbene derivatives are synthesized, including thiourea, azine, and metal complexes with W(0), Pd(II) and Hg(II). Spectroscopic, structural and electrochemical properties in this series of compounds are compared with those of recently published analogous but methylene-spacered benzimidazoline-2-ylidene derivatives, indicating significant electronic communication between the carbene moiety and the N -ferrocenyl substituent.

Efficient telomerization of 1,3-butadiene with alcohols in the presence of in situ generated palladium(0)carbene complexes

The palladium-catalyzed telomerization of 1,3-butadiene with alcohols has been studied in presence of palladium and imidazolium salts, which form in situ carbene ligands. Among the different imidazolium salts tested 1,3-dimesitylimidazolium chloride (7), 1,3-bis(ferrocenylmethyl)benzimidazolium tetraphenylborate (12) and 1,3-bis(2-ferrocenylethyl)benzimidazolium bromide (13) gave the best yields of the desired octadienyl ethers. Significantly improved regioselectivities for the linear octadienylethers are obtained in the reaction of 1,3-butadiene and methanol compared to the previously optimized palladium/triphenylphosphine catalyst. Using n-butanol and iso-propanol the palladium carbene catalysts lead to a considerable increase in the corresponding telomerization products compared to standard palladium/triphenylphosphine catalysts.

Synthesis and electrochemistry of ferrocenyldiazabutadiene metal carbonyl complexes (Fc-DAB)M(CO)4 [M=Cr,Mo,W]

Abstract The synthesis, characterization (UV–Vis, IR, MS, NMR), and electrochemistry (CV, DPV) of ferrocenyl diazabutadienes and their chromium, molybdenum, and tungsten tetracarbonyl complexes are reported in this study. The properties of these compounds are compared to those of p -methoxyphenyl diazabutadiene analogues, (a) allowing the clear distinction between ferrocene-based and diazabutadiene metal carbonyl localized redox processes in these multimetallic complexes, and (b) showing that the electronic interaction between the peripheral ferrocenyl substituents increases upon complexation to the Group 6 transition metal tetracarbonyl moieties.

First Examples of a New Family of Redox‐Functionalised Chelate Complexes Based on a 1,1′‐Ferrocenediyl‐Bridged Di(amido) Ligand

Treatment of Fe[(C5H4)NHPh]2 (1H2) with M(NMe2)4 (3a: M = Ti, 3b: M = Zr) in benzene afforded the chelates (1)Ti(NMe2)2 (4) and (1)Zr(NMe2)2(HNMe2) (5), respectively. Chelate 5 was cleanly oxidised by ferrocenium hexafluorophosphate in acetonitrile. Treatment of 5 with two equivalents of [Me2NH2]Cl (6) in benzene afforded (1)ZrCl2(HNMe2) (7). The chelates 5 and 7 were characterised by X-ray structure analyses. The new redox-active chelate complexes are precatalysts for the polymerisation of ethylene.

Reversible switching of the first hyperpolarisability of an NLO-active donor–acceptor molecule based on redox interconversion of the octamethylferrocene donor unit

Compound 1, containing an octamethylferrocene donor linked to a nitrothiophene acceptor via an ethenyl linker, shows a static first hyperpolarisability β0 of 95(±10) × 10−30 esu, which is reduced to 10(±2) × 10−30 esu on oxidation of the octamethylferrocene unit; this provides for a simple redox-based switching of the NLO characteristics of the compound.

Donor–acceptor complexes incorporating ferrocenes: spectroelectrochemical characterisation, quadratic hyperpolarisabilities and the effects of oxidising and reducing agents

The donor–acceptor complexes [Fe(C5H5){C5H4QNHM(NO)(TpMe,Me)X}] {TpMe,Me = tris(3,5-dimethylpyrazolyl)borate; Q = nothing, M = Mo, X = Cl, Br, I; M = W, X = Cl; Q = C6H4, M = Mo, X = Cl, Br, I; M = W, X = Cl; Q = CHCHC6H4 or NNC6H4, M = Mo, X = Cl), which contain 16-valence electron metal nitrosyl centres, [Fe(C5H5){C5H4QpyMo(NO)(TpMe,Me)Cl}] (py = 4-pyridyl; Q = CHCH, CHCHCO, NCH and C6H4CHCH), [Fe(C5Me4H){C5H4CHCHpyMo(NO)(TpMe,Me)Cl}] and [Fe(C5Me4H)(C5Me4QpyZ)] {Q = CHCH or CHN, Z = Mo(NO)(TpMe,Me)Cl or W(CO)5; Q2,4-CHCH(C4H2S)CHCH, Z = W(CO)5 or Me+I−}, some of which contain 17-valence electron molybdenum nitrosyl centres, and [Fe(C5Me4H){C5Me4CHCH(C4H2S)CHCHpy}], have been characterised electrochemically, by their electronic spectra, and spectroelectrochemically. Hyper-Rayleigh scattering was used to determine the first hyperpolarisability, β, the data showing that (a) β is dependent on the metal in the acceptor fragment, (b) β increased when Cl or Br was replaced by I and (c) β increased when the number of methyl groups on the cyclopentadienyl rings increased. The β-values for comparable complexes containing {Mo(NO)(TpMe,Me)Cl} and {W(CO)5} moieties were similar. Chemical oxidation of the ferrocenyl or chemical reduction of the molybdenum nitrosyl acceptor fragments in selected complexes caused a reduction of between 25% and 100% in the NLO response. X-Ray structural studies of [Fe(C5H5){C5H4NHMo(NO)(TpMe,Me)Cl}] (P) and [Fe(C5Me4H){C5Me4CHCHpyMo(NO)(TpMe,Me)Cl}] (P) are reported.

Reactivity and Structure of Diferrocenylamine and N,N - Diferrocenylcarbamoylchloride

The reactivity of diferrocenylamine has been investigated aiming at the preparation of novel diferrocenylamino compounds, including nitrenium salts, amino radicals, transition metal amides, carbamato ligands, and others. However, diferrocenylamine is unexpectedly difficult to derivatize; only simple metalation by butyl lithium, alkylation by iodomethane, and chloroformylation by phosgene were possible. X-ray crystal structures are reported for the starting diferrocenylamine, and for the derivatives diferrocenylmethylamine and N,N diferrocenylcarbamoylchloride.