247 research outputs found
Reactions of a phosphinito bridged diplatinum(I) complex with coinage metal electrophiles
No full textWe have recently described the synthesis of the complex
[(PHCy2)Pt1(m-PCy2){k2P,O-m-P(O)Cy2}Pt2(PHCy2)] (Pt-Pt)
(1), the first unsymmetrical phosphinito bridged Pt(I) species.[1]
The phosphinito bridge differentiates the charge distributions on
the two platinum atoms as confirmed by NMR spectroscopy
(dPt(1) = -4798 ppm, dPt(2) = -5207 ppm) and DFT studies. Complex
1 shows a rich chemistry as it reacts with nucleophiles [PHCy2,
PCy3, P(S)HCy2],[2] protic species HX [P(OH)Cy2, PhSH, HF,
HCl, HBr, HI, HBF4],[3, 4] and small molecules such as H2.[5]
Recently, we started investigations on the reactivity of complex 1
towards Au and Ag based electrophiles.
In this communication, it will be shown that, differently
from the isolobal H+ (which attacks the phosphinito oxygen and
migrates onto the Pt-Pt bond),3 the [Ag(PPh3)]+ electrophile
attacks complex 1 selectively to the Pt2-mP bond to afford the
cationic cluster [(PHCy2)Pt1(m-PCy2){k2P,O-m-P(O)Cy2}Pt2{m-
-Ag(PPh3)}(PHCy2)]+ (Pt–Pt) (2+) in which the [Ag(PPh3)]+
moiety bridges the mP-Pt2 bond. Analogous reactivity is observed
also when phosphane free electrophiles such as AgOTf, AgBF4,
AgClO4 and AgCl are used. Moreover, the reactivity of 1 towards
Au(I) electrophiles such as AuCl and [Au(PPh3)Cl] was dependent
on the reagent and on the experimental conditions.
references:
1. Gallo, V.; Latronico, M.; Mastrorilli, P.; Nobile, C. F.;
Suranna, G. P.; Ciccarella, G.; Englert, U.; Eur. J. Inorg.
Chem., 2005, 4607–4616.
2. Gallo, V.; Latronico, M.; Mastrorilli, P.; Nobile, C. F.;
Polini, F.; Re, N.; Englert, U.; Inorg. Chem., 2008, 47,
4785–4795.
3. Latronico, M.; Polini, F.; Gallo, V.; Mastrorilli, P;
Calmuschi-Cula B.; Englert, U.; Re, N.; Repo T.,
Raisanen M.; Inorg. Chem., 2008, 47, 9979-9796.
4. M. Latronico, P. Mastrorilli, V. Gallo, M.M.Dell’Anna,
F. Creati, N. Re, U. Englert, Inorg. Chem. 2011, 50,
3539–3558
5. Mastrorilli P., Latronico M., Gallo V., Polini F., Re N.,
Marrone A., Gobetto R., Ellena S.. J. Am. Chem. Soc.
2010, 132, 4752–476
Reactivity of nickel (II) diphosphine complexes towards alkoxides: a new route to the synthesis of nickel(0) compounds through nickel(II) alkoxides
No full textReaction of [Ni(L-L)Cl2] [L-L = Ph2P(CH2)nPPh2, n = 2 (dppe) or 3 (dppp)] with NaOR (R = Me, Et or Pr(i)) under a dinitrogen atmosphere afforded [Ni(L-L)2], Ni(OR)2 and aldehyde (or acetone when R = Pr(i)) in 1 : 1 : 1 ratio, showing the peculiar reducing effect of alkoxide promoted by the chelating property of the phosphorus ligand. The reaction of NaOMe with [Ni(dcpe)Cl2] [dcpe = 1,2-bis(dicyclohexylphosphino)ethane] afforded mainly [Ni2(dcpe)3] when carried out in the absence of free diphosphine, and [Ni(dcpe)2] in the presence of free diphosphine. The reaction always yields the nickel(o) species [Ni(L-L)(CO)2] when it is carried out under a carbon monoxide atmosphere. The intermediate formation of unstable alkoxo(diphosphine)nickel(II) complexes has been demonstrated by recording the P-31 NMR spectra of the reacting solutions at low temperature; in the case of the reaction of [Ni(dcpe)Cl2] with NaOMe only, it was possible to isolate as a solid the [Ni(dcpe)(OMe)2] Complex, which has been fully characterized by analytical and spectroscopic (IR and H-1, P-31 NMR) methods. A possible route by which nickel(o) complexes could be formed is discussed
Aerobic epoxidation of olefins catalysed by polymerizable -ketoesterate complexes of Iron(III), Nickel(II) and Cobalt(II)
No full textSupported catalysts from polymerizable transition metal complexes
No full textThis review covers the last 12 years of research on the synthesis and use of heterogeneous catalysts obtained by co-polymerization of suitable metal containing monomers (MCM). The catalytic applications of these supported metal complexes are subdivided into three areas. Hydrogenation of alkenes and functionalized olefins are covered first. Oxidation of several substrates such as olefins, sulfides, alcohols, and aldehydes are then considered. Of particular interest in this framework is the use of chiral salen metal containing monomers for the stereoselective epoxidation of hindered olefins. Alkene and alkyne polymerizations, Heck and Heck-type reactions, allylic alkylation, and Michael additions are discussed in the field of carbon-carbon bond forming reactions. A common factor emerging from this survey is the application of metal containing monomers for the synthesis of molecularly imprinted polymers to be used as catalysts or catalyst supports
Polymer Supported Catalysts Obtained from Metal-Containing Monomers
No full textThis review summarizes the progress made in the last eight years on the synthesis and use in catalysis of polymer supported metal complexes obtained by co-polymerization of metal-containing monomers (MCMs) with suitable co-monomers and cross-linkers. These materials are divided into four important classes: microporous organic polymers, molecularly imprinted polymers (MIPs), macropouros organic polymers, polymers obtained by ring opening metathesis polymerization (ROMP). Although the MIPs have essentially a macroporous structure, they constitute a separate group of catalysts for their peculiar way of synthesis. The discussion focuses on the efficiency and reusability of all these potentially recoverable catalysts
Aerobic oxidation of alkanes by aldehyde/dioxygen system in the presence and in the absence of metal catalyst
No full textA Pd(AcO)2/t-Bu3P/K3PO4 catalytic system for the control of Suzuki cross-coupling polymerisation
No full textThe initiation of the Suzuki cross-coupling polymerisation with a fluorene-based AB-type monomer was finely tuned within the chain-growth regime by the suitable control of the species generated by the Pd(AcO)2/t-Bu3P/K3PO4 catalytic system. The prototypical poly(9,9-di-n-octyl-fluorene) was obtained with extremely fast (1 min) polymerisation rates, excellent polydispersities (1.16) and molecular weights dependent on the monomer/catalyst molar ratio, without the need to resort to formal chain-initiators
N-substituted bis(diphenylphosphanyl)amine ligands bearing the thioether functional group: coordination modes in PtCo2 and PtMo2 base clusters
No full textChiral Switchable Catalysts for Dynamic Control of Enantioselectivity
No full textAmong the artificial switchable catalysts, those catalysts whose activity can be switched by an external stimulus, only a few cases offer the possibility to develop an effective chiral switchable system that could selectively accelerate the formation of a given enantiomer in one state, whereas in the other state it prefers accelerating the formation of the opposite enantiomer. Many pharmacological investigations need both enantiomers to study potentially different activities and side effects. Thus, chiral switchable catalysts could be a very important tool to achieve this goal because their use will eliminate the need to have the two enantiomers of a designed catalyst. This perspective summarizes, discusses, and emphasizes important developments in the chiral switchable catalyst area for the dynamic control of enantioselectivity, highlighting their advantages and showing some perspectives of this field that is still in its infancy
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