Organometallic Cations Research Articles

On the relationship of the equilibrium constants of exchange reactions involving HX-acids and their organometallic derivatives L nMX with the absolute and chemical hardness of corresponding anions and cations

The exchange equilibria: Ph 3Sn−X+Ph 3Pb−SC 6H 4F−4 ⇌ Ph 3Pb−X+Ph 3Sn−SC 6H 4F−4 (X = OH, Cl, Br, I) have been studied in CHCl 3 by 19F NMR. Good correlations of equilibrium constant logarithm with the Pearson parameters of absolute and chemical hardness have been found. On the basis of these relationships and general consideration of exchange equilibria it has been shown that the study of exchange reactions involving hard and soft HX-acids and their L n M-derivatives permits study of quantitative regularities in ligand influence on the hardness of organometallic cations.

The Magic Salt Effects of Sodium Hexafluorophosphate

Abstract The Na+PF6− salt changes the course of reactions between neutral or ionic substrates. Examples of reactions include superoxide radical chemistry, disproportionation, and C[sbnd]H and C[sbnd]O bond activation. This special salt effect is usually quantitative and sometimes catalytic. When compared to other salts, Na+PF6− by far gives the most spectacular results, due to the small size of Na+ as compared to large organometallic cations.

An isolable organometallic cation radical in which a C4 chain conducts charge between two chiral and configurationally stable rhenium termini

An isolable organometallic cation radical in which a C4 chain conducts charge between two chiral and configurationally stable rhenium termini

New synthetic routes to cationic arene ?-complexes of transition metals

A review is given of the authors' studies on the development of new methods for the synthesis of cationic arene complexes of transition metals. The synthesis in strong protic acids facilitated obtaining π-arene cations of Mn, Re, Ru, Os, Co, Rh and Ir. New nonacidic methods allowed the set of available cationic arene π-complexes of Mn, Ru, Rh and Ir to be increased considerably. Based on the developed methods a number of previously unknown binuclear organometallic cations are obtained.

The ions MCp2+ (M = scandium, lanthanum): significantly bent sandwich species

Ab initio calculations show that the hypothetical organometallic cations MCp 2 + (M=Sc, La) have bent-metallocene structures. This is due to covalent σ-bonding contributions involving the totally symmetric metal d σ orbitals, whic favor bent geometries

A unique example of an octahedral iron(II) complex containing four triflate anions and two nitrile-like organometallic cations

The action of MeSO3CF3 on [Fe2(cp)2(CO)2(µ-CO){µ-C(CN)SMe}]1(cp =η5-C5H5) yields [Fe2(cp)2(CO)2(µ-CO){µ-C(CN)SMe2}][SO3CF3]2. The sulphonium cation is also obtained, trapped in the unusual triflate complex Fe(OSO2CF3)4{Fe2(cp)2(CO)2(µ-CO)[µ-C(CN)SMe2}2]3, by treating the thiolcarbamate [Fe2(cp)2(CO)2(µ-CO){µ-C(CN)N(Me)C(O)SMe}]4 with MeSO3CF3. The X-ray crystal structure of 3 shows the iron(II) centre co-ordinated by four O-bonded triflate anions and by two, mutually trans-disposed, N-co-ordinated organometallic cations in an octahedral geometry.

Synthesis and characterisation of new conductors based on M(dmit) 2 anion. (H 2dmit=4,5-dimercapto-1,3-dithiole-2-thione, M=Ni,Cu,Pd,Pt)

The chemistry of the complexes of the ligand 4,5-dimercapto-1,3-dithiole-2-thione has generated great interest amongst chemists for the past few years. In particular, it is noteworthy that TTF[Ni(dmit) 2] 2 (TTF= tetrathiafulvalene) becomes superconductor at low temperature and under pressure. Introduction of large organic and organometallic cations as counterparts into the partially oxidised metallate anion salts seems to be of interest because of possibilities of a new arrangement of the anions in the crystals. We report here the synthesis of a series of new complexes based on [M(dmit) 2] anions using large cations PPN + and cobalticinium + [PPN=bis(triphenylphosphine)iminium chloride]. Conductivity, magnetic and electrochemical data will be presented.

The reaction of [(η 5-cyclohexadienyl)Fe(CO) 3] +BF 4− with 2-methyl-2-nitrosopropane: an unexpected oscillating reaction

The reaction of 2-methyl-2-nitrosopropane with the organometallic cation [(η 5-cyclohexadienyl)tricarbonyliron] + yields the bis(t-butyl)nitroxide radical which is detected by ESR spectroscopy. The intensity of the ESR signal varies in an oscillatory manner with time and the ESR silent period between oscillations ranges from 15 minutes to one hour, depending on the relative concentrations of the reagents. Some years ago, Turcsanyi proposed ( Acta Chim., Acad. Scient. Hungar., 110 (1982) 305, Chem. Abs. 97 188877w) that a RNO/RNHOH system might exhibit oscillatory behaviour and the data presented are an experimental realization of that prediction. A mechanistic rationale is proposed to account for the observations.

ChemInform Abstract: Hydrated σ‐Bonded Organometallic Cations in Organic Synthesis. Part 2. Allylstannation of Aldehydes by Crotyltin Chlorides in Acid Media.

AbstractThe title reaction is carried out in the presence of aqueous 0.1‐4.0 M HClO4.

ChemInform Abstract: Efficient Ion Exchangers and Receptors for Organic and Organometallic Cations.

Abstract"Free" (Me3Sn)+ ions can be exchanged with surprising ease in polymeric metal cyanides such as (I) by reaction with cations such as (NEt4)+ or (Co(π‐C5H5)2)+.

Hydrated σ-bonded organometallic cations in organic synthesis: II. Allylstannation of aldehydes by crotyltin chlorides in acid media

Allylstannation of three aldehydes RCHO (RC2H5, (CH3)2CH, and (CH3)3C) with crotyltin chlorides Bu3-nClnSnCH2CHCHCH3, n = 1, 2, and 3, has been carried out in the presence of aqueous 0.1–4.0 M HClO4. The stereochemical course of these reactions, to give the threo / erythro alcohols RCH(OH)CH(CH3)CHCH2 and/or the E/Z alcohols RCH(OH)CH2CHCHCH3, depends on the number, n, of the chlorine atoms bonded to tin and on the concentration of perchloric acid. In 0.1 M HClO4, the threo / erythro isomer pair is obtained. With increasing acid concentration, the threo / erythro pair is gradually replaced by the E/Z isomer pair, which is the sole product in 4 M HClO4. However, in most of the examined cases the ratio anti / syn = (threo + E)/(erythro + Z) remains constant for any given aldehyde and crotyl compound. Stereoselectivity, which is fairly good in some cases, is determined by the nature of the aldehyde: syn-convergence occurs with pivalaldehyde, and anti-convergence with isobutyraldehyde. No stereoselection is found in the case of propanaldehyde.

Efficient Ion Exchangers and Receptors for Organic and Organometallic Cations

“Free” (CH3)3Sn⊕ ions can be exchanged with surprising ease in polymeric metal cyanides, as demonstrated by reactions (a) and (b). Host–guest complexes, in which an inorganic solid acts as host and an organometallic or organic cation is the guest, are of considerable interest with respect to the development of materials with nonlinear optical properties.

Charge distribution in bimetallic organometallic cations

Charge distribution in two monocationic bimetallic organoiron complexes, prepared by transfer of Fp+ to Fp acyl and vinyl species [Fp = Fe(CO)2(C5H5)], have been studied by 57Fe Mössbauer spectroscopy, demonstrating that a considerable degree of polarisation is present in linear organic π-systems interposed between organometallic donor and acceptor groups.

ChemInform Abstract: Hydrated σ‐Bonded Organometallic Cations in Organic Synthesis. Part 1. Allyl‐, Crotyl‐, 1‐Methylallyl‐, Cyclohex‐2‐enyl‐, and Cinnamyl‐Stannation of Carbonyl Compounds (I) in Water.

ChemInform Abstract: Hydrated σ‐Bonded Organometallic Cations in Organic Synthesis. Part 1. Allyl‐, Crotyl‐, 1‐Methylallyl‐, Cyclohex‐2‐enyl‐, and Cinnamyl‐Stannation of Carbonyl Compounds (I) in Water.

Hydrogen and coordination bonds in isostructural systems. Are hydrogen bonds unique?

Reliable spectral criteria which allow comparison of the hydrogen and coordination bonds in isostructural systems are suggested. The model systems consist of ArXH and ArXMR n (X = O, S, N; M = Hg, Sn, Pb, Sb; Ar = C 6H 4Y where Y = COR, NO 2, C 5H 4N, etc.) which interact with various N-, P- and O-bases. The conditions on which the ν XM vibrations are local, have been established. Examination of thiol derivatives reveals the similarity of spectral (IR, Raman) effects for coordination and hydrogen bonds in the ν XM and ν XH regions, respectively. The character of dependence of a proton and a bulky organometallic cation transfer on medium, a heteroatom X or a base is shown to be similar. Some quantitativeand qualitative relationships between XH and XM bond polarities and the capacity to form complexes, ionic pairs or ions are found. Comparison of spectral properties of isostructural systems with hydrogen and coordination bonds does not reveal the uniqueness of the H bond.

Hydrated σ-bonded organometallic cations in organic synthesis: I. Allyl-, crotyl-, 1-methylallyl-, cyclohex-2-enyl-, and cinnamyl-stannation of carbonyl compounds in water

Homoallylic alcohols can be prepared in water by allyl-, crotyl-, 1-methylallyl-, cyclohex-2-enyl-, or cinnamyl-stannation of such carbonyl compounds as aldehydes, dialdehydes, and ketones, as well as acetals. The procedure is based on: Bu 2RSnCl + R′COR″ + 1 2 H 2O → R(HO)CR′R″ + 1 2 (Bu 2SnCl) 2O ↓ where R = allyl, crotyl, 1-methylallyl, cyclohex-2-enyl, or cinnamyl group, R′ = H or alkyl group, R″ ≠ R′ = alkyl group. In most cases, the reaction products are obtained rapidly in high yields (80–100%). Hydrated organometallic cations Bu 2RSn + (aq) are partly involved. These results, together with those already published on 2-propynyl- and allenyl-stannation, indicate the value of this procedure.

Rhodium and iridium oxometallates- A new class of solid microporous materials

Organometallic Keggin ion complexes, exemplified by [(Ph 3P) 2Rh(CO)] 4SiW 12O 40 and [(Ph 3P) 2IrH 2] 3PW 12O 40 have been characterized by solid state NMR and X-ray absorption spectroscopy. They constitute a new class of chemically microporous solids and illustrate the use of large molecular metal oxide clusters to form extensible lattices in which coordinatively unsaturated organometallic cations may be stabilized and studied. In some cases, these cations are mobile and form bimetallic species. The reactions of those materials in olefin isomerization, hydroformylation, hydrogenation, dehydrogenation and C-H activation processes are described.

The relative electrophilic reactivities of tropylium cation and its (OC)3M π-complexes: kinetic studies of alkoxide transfer and reversible nucleophilic addition

π-Complexation of the tropylium cation (Tr)+ with an (OC)3Cr group increases thermodynamic stability (ΔpKR +ca. 4.3 in methanol) and reduces reactivity towards abstraction of methoxide ion from Malachite Green methyl ether (MG)OMe (krel.ca. 110) in MeNO2–MeCOEt (40 : 60 v/v) and nucleophilic exo-addition of methanol (krel.ca. 2 100) in methanol. The organometallic cation (1a) is stable in aqueous solutions of pH < ca. 6, but at higher pH is converted irreversibly into (OC)3Cr complexes (5) and (6) of ditropyl. The same complexes are formed on reaction of (1a) with 1,8-bis(dimethylamino)naphthalene. The relative rates of transfer of methoxide ion from (MG)OMe to {(η-Tr)Cr(CO)3}+, {(η-Tr)Mo(CO)3}+, and {(η-Tr)W(CO)3}+ in MeNO2–MeCOEt (40 : 60 v/v) are 1 : 10 : 6, respectively. The rates of transfer to (Tr)+ of alkoxide ion from (η-7-exo-alkoxycycloheptatriene)Cr(CO)3 complexes (2a–d) in MeCN decrease through the series: alkoxy = methoxy > ethoxy > isopropoxy > t-butoxy, but the overall rate change is only about five-fold. In methanol, the 7-exo-methoxycycloheptatriene complex (2a) is about ten times more reactive towards acid heterolysis than is methyl tropyl ether. This conversion is general acid-catalysed. in aqueous solutions of pH > ca. 6, the rate of spontaneous heterolysis of the ether (2a) is substantially faster than that of consumption of the resulting cation (1a) which increases with increasing pH. The 7-endo-methoxy stereoisomer (3) is inert to acid heterolysis in aqueous solutions to give the cation (1a), but undergoes decomplexation to give (Tr)+.

Mass spectrometric investigation of adduct formation by methylated cyclodextrins

FABMS has been employed to detect the formation of supramolecular adducts between methylated cyclodextrins and (i) organic ammonium salts, (ii) organometallic cations, and (iii) neutral metalloorganic complexes. This is a facile technique for studying the second sphere coordination of transition metal complexes by chemically-modified cyclodextrins.

Übergangsmetallkomplexe instabiler Ylide, X [1] Chemische und elektrochemische Untersuchungen zu den Redox-Eigenschaften cyclischer Tetracarbonylchrom-Ylidchelatkomplexe / Transition Metal Complexes of Unstable Ylides, X [1] Chemical and Electrochemical Investigations of the Redox Properties of Cyclic Tetracarbonylchromium-Ylide-Chelate-Complexes

Abstract Treatment of the ylide chelate complexes (CO)4 (1) with (C5H5)2Fe+PF6 - leads to the organometallic radical cations 2. The oxidation process of 1 is also checked electrochemically by means of cyclovoltammetry, which exhibits a reversibel one electron oxidation between -0.1 and +0.3 V vs. SCE. These potentials are more negative than in any other complex of the general type Cr(CO)4L2 (L e.g. = PR3, CNR).