Switchable Polymerization of Norbornene Derivatives by a Ferrocene‐Palladium(II) Heteroscorpionate Complex

The ferrocene-chelating heteroscorpionate complex [(fc(PPh2){BH{(3,5-Me)2pz}2})PdMe] {(fcP,B)PdMe, fc = 1,1′-ferrocenediyl, pz = pyrazole} catalyzes the addition polymerization of norbornene and norbornene derivatives upon oxidation with [AcFc][BArF] {acetyl ferrocenium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate}. In situ reduction of [(fcP,B)PdMe][BArF] in the presence of a substituted norbornene results in significant decrease of catalytic activity. Addition of one equivalent of oxidant restores the activity

CH Bond Activation of Hydrocarbons Mediated by Rare-Earth Metals and Actinides: Beyond σ-Bond Metathesis and 1,2-Addition

© 2015 Elsevier Inc. This review discusses C. H bond activation of hydrocarbons mediated by rare-earth metal complexes with an emphasis on type of mechanisms. The review is organized as follows: in the first part, C. H bond activations mediated by rare-earth metals and actinides following traditional reaction pathways, such as σ-bond metathesis and 1,2-addition, are summarized; in the second part, nontraditional C. H bond activation examples are discussed in detail in order to understand the underlying mechanisms. The scope of the review is limited to rare-earth metals and actinides, but, in some cases, closely related reactivity of group 4 metals will be included for comparison. The purpose of the review is not only to provide a brief overview of C. H bond activation by f-elements but also to bring to attention unusual C. H bond cleavage reactivity following mechanisms different than σ-bond metathesis and 1,2-addition

P4 activation by lanthanum and lutetium naphthalene complexes supported by a ferrocene diamide ligand

Two rare-earth (La and Lu) naphthalene complexes supported by a ferrocene diamide ligand activate P4 under ambient conditions to form M 3P7 species exclusively. The resulting complexes feature a Zintl-type polyphosphide P73- unit stabilized by three lanthanide fragments. The reported metal complexes were characterized by X-ray crystallography, multinuclear NMR spectroscopy, and elemental analysis. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Rare earth arene-bridged complexes obtained by reduction of organometallic precursors

Rare earth chemistry has witnessed remarkable advances in recent years. In particular, ancillary ligands other than cyclopentadienyl derivatives have been introduced to the organometallic chemistry, and their complexes exhibit distinct reactivity and properties compared to the metallocene or half-sandwiched analogs. This chapter reviews arene-bridged rare earth complexes with an emphasis on those compounds obtained by reduction reactions. A particular emphasis is placed on rare earth complexes supported by 1,1'-ferrocenediyl diamides since they show the most diverse chemistry with arenes: Fused arenes, such as naphthalene and anthracene, formed inverse-sandwiched complexes, in which the arene is dianionic; weakly conjugated arenes, such as biphenyl, p-terphenyl, and 1,3,5-triphenylbenzene, were unexpectedly reduced by four electrons and led to 6-carbon, 10π-electron aromatic systems; on the contrary, (E)-stilbene, which has a carbon-carbon double bond between the two phenyl rings, could only be reduced by two electrons, which were located on the carbon-carbon double bond instead of the phenyl rings. The reactivity of some rare earth arene-bridged complexes is also discussed with noticeable examples being the activation of white phosphorus (P4) by rare earth naphthalene complexes. Stoichiometric P4 activation led to polyphosphide (P84-P84- or P73-P73-), which could then be transferred to phosphorus-containing organic molecules. © 2014 Elsevier B.V

Switchable Polymerization of Norbornene Derivatives by a Ferrocene-Palladium(II) Heteroscorpionate Complex

The ferrocene-chelating heteroscorpionate complex [(fc(PPh2){BH{(3,5-Me)2pz}2})PdMe] {(fcP,B)PdMe, fc = 1,1′-ferrocenediyl, pz = pyrazole} catalyzes the addition polymerization of norbornene and norbornene derivatives upon oxidation with [AcFc][BArF] {acetyl ferrocenium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate}. In situ reduction of [(fcP,B)PdMe][BArF] in the presence of a substituted norbornene results in significant decrease of catalytic activity. Addition of one equivalent of oxidant restores the activity

In situ synthesis of lanthanide complexes supported by a ferrocene diamide ligand: Extension to redox-active lanthanide ions

Reliable transformation of low-cost rare-earth metal oxides to organometallic rare-earth metal complexes is a prerequisite for the advancement of non-aqueous rare-earth metal chemistry. We have recently developed an in situ method to prepare rare-earth alkyl and halide precursors supported by a diamidoferrocene NNTBS, 1,1′-fc(NSiMe2tBu)2, as an ancillary ligand. Herein, we extended the scope of this method to other lanthanide ions including those that are redox active, such as cerium, praseodymium, samarium, terbium, thulium, and ytterbium. Specifically, samarium trisbenzyl could be generated in situ and then converted to the corresponding samarium benzyl or iodide complexes in good yield. However, it was found that ytterbium trisbenzyl could not be formed cleanly and the consequent conversion to ytterbium iodide complex was low yielding. By adapting an alternative route, the desired ytterbium chloride precursor could be obtained in good yield and purity

Highly Active Yttrium Catalysts for the Ring-Opening Polymerization of ε-Caprolactone and δ-Valerolactone

The activity of several yttrium alkoxide and aryloxide complexes supported by a ferrocene-based ligand incorporating two thiol phenolates, thiolfan (1,1′-bis(2,4-di-tert-butyl-6-thiomethylenephenoxy)ferrocene), was studied. The tert-butoxide complex could only be isolated in the ate form, while a monophenoxide complex could be obtained for OAr = 2,6-di-tert-butylphenolate. The synthetic utility of these yttrium complexes has been demonstrated by the ring-opening polymerization of cyclic esters, with a high activity toward ε-caprolactone and -valerolactone being found for the yttrium phenoxide complex

Investigation of the electronic structure of mono(1,1′- diamidoferrocene) uranium(IV) complexes

The electronic structure of several mono(1,1′-diamidoferrocene) uranium complexes (NNR)UX2 (NNR = fc(NR) 2, fc = 1,1′-ferrocenediyl, R = SiMe3, Si tBuMe2, SiMe2Ph, X = I, CH2Ph), (NNTBS)UI(OAr) (OAr = 2,6-di-tert-butylphenoxide), and (NN TBS)U(CH2Ph)(OAr) was investigated by electrochemistry, electronic absorption and vibrational spectroscopy, and DFT calculations. Similar metrical parameters were observed for (NNTBS)U(CH 2Ph)2 and (NNDMP)U(CH2Ph) 2 (and also for the previously reported (NNTMS)UI 2(THF), (NNTBS)UI2(THF), and (NN TBS)U(CH2Ph)(OAr)) that translate in similar DFT parameters (bond orders, metal charges) despite some small differences observed by electrochemistry and IR or electronic absorption spectroscopy. © 2013 American Chemical Society

Synthesis of ferrocene-functionalized monomers for biodegradable polymer formation

Cyclic carbonate and δ-valerolactone substrates functionalized with ferrocene were synthesized via alkyne-azide "click" cycloaddition. The cyclic carbonates were polymerized using 1,8-diazabicycloundec-7-ene, 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexylthiourea, and benzyl alcohol. The resulting polymers were characterized by GPC, NMR spectroscopy, and cyclic voltammetry studies. It was found that polycarbonate molecular weights fall in the range of 4.1-5.2 × 10 g mol with polydispersities as low as 1.26. Electrochemistry studies allowed us to identify the monomer/polymer pair with the most desirable redox potential for biological studies. 3 -