Clifford W. Fong

Sulfur dioxide insertion into carbontin bonds: II. Rearrangements accompanying insertion☆

A number of allylic, allenylic and 2-propynylic (R′) derivatives of tin of the type R3SnR′ have been synthesized, and shown to undergo ready insertion of sulfur dioxide into the SnR′ bond. Rearrangement accompanies insertion so that the products have the alternate allylic, 2-propynylic and allenylic structures respectively. Di-insertion occurs only when groups attached to tin are quite susceptible to electrophilic cleavage. NMR data for the compounds are reported.

Sulfur dioxide insertion into carbon-lead bonds

The insertin of sulfur dioxide into a variety of carbon-lead systems has been studied, and all products possess O-sulfinato structures. Spectroscopic (IR, mass spectra and PMR) and molecular weight data strongly suggest the presence of bridging SO2 and essentially planar R3Pb moieties. Relative rates of insertion into a number of differing RPb bonds are completely in line with an electrophilic cleavage description of the insertion process. Differences from (e.g. ready polyinsertion)_ and similarities with the behaviour of analogous organotin systems are rationalised.

Sulfur dioxide insertion into aryl carbon-tin bonds: kinetics and mechanism

A kinetic study of the insertion of sulfur dioxide into the aryl carbon-tin bond of a species of 3- and 4-substituted phenyltrimethyl stannanes in anhydrous methanol has been conducted. The reaction is cleanly second order in this solvent (first order in each of stannane and sulfur dioxide) and the second order rate constants show an excellent correlation with σ+, indicating an electrophilic insertion reaction. The low p value and a positive salt effect on the rate of insertion suggest a four centeredSEi transition state with some polar character. Sulfur dioxide is located in the electrophile reactivity series, CH3,COOH < SO2 < HCl < < I2 < < BR2 for this particular system. Whilst the insertion reaction in methanol is a second order process, the kinetic situation in benzene is more complex, with k2(obs) increasing with [SO2], and may be attributable to changes in the dielectric properties of the medium. The stereochemistry of insertion into a vinyltin bond is shown to involve essentially complete retention of configuration at carbon, as demanded by an SEi process.

Sultones et sultines organometalliques VII. Reactions d'insertion de l'anhydride sulfureux dans la liaison silicium-carbone: Sultines organosiliciques

Abstract The behaviour of some substituted silacyclobutanes with respect to sulfur dioxide is studied. The alkylated, arylated and alkoxylated derivatives of silacyclobutane react with SO 2 to give the first “silasultines” (2-oxo-4-sila-1,2-oxathianes). The structure and the configurational analysis of the insertion products are proved by chemical and physicochemical ways. The mechanism of the SO 2 insertion is discussed.

Sulfur dioxide insertion into carbontin bonds : I. Scope of the reaction and nature of the products

Abstract A range of tetraorganotin compounds, embodying extensive variety in the organic groups, have been shown to undergo insertion of sulfur dioxide into the carbontin bond. The structures of the insertion products have been arrived at from considerations of vibrational, nuclear magnetic resonance and mass spectroscopy. The products are O -sulfinate in type, but aggregated in the solid phase and solution so that tin generally achieves a coordination number of five, with an essentially planar R 3 Sn moiety.

Syntheses of carbon monoxide, cyclopentadienyl and related compounds of transition metals containing the η1- or η2-dimethylaminomethyl ligand

A series of chromium, molybdenum, tungsten, and iron carbonyl and substituted carbonyl compounds containing the dimethylaminomethyl, CH2NMe2, ligand has been synthesized using the reactive immonium compound, di-methyl(methylene)ammonium iodide. The dimethylaminomethyl group has been shown to function as a one-electron donor in compounds such as (η5-C5H5)Mo(CO)3(η′-CH2NMe2) and as a three-electron donor ligand in compounds such as [Mo(CO)3(bipy)(η2-CH2NMe2)]+I–.Interaction of Cr and Fe carbonyl dianions with the immonium compound has been shown to form metal–carbene compounds.

σ-Bonded organotransition metal ions. Part XV. Preparation and fluorine-19 nuclear magnetic resonance spectra of some monomeric anionic, cyanide-bridged dimeric anionic, and related fluorobenzylcobalt(III) complexes

Fluorobenzylcobalt(III) complexes of the type (i) 4-FC6H4CH2Co(dmgH)2B–, where dmgH is the conjugate base of dimethylglyoxime and B = CN, N3, NCO, Cl, Br, I, NO2, NCS; (ii) 4-FC6H4CH2Co(dmgH)2CNCo(dmgH)2R–, where R = Me, CH2C6H4F, CH2C6H4NO2; (iii) RCo(dmgH)2CNCo(dmgH)2CH2C6H4F–, where R = Me, CH2C6H4NO2, CCPh; (iv) 4-FC6H4CH2Co(dmgH)(dmgH2)B, where B = CNCo(dmgH)2CH2C6H4F, CNCo(dmgH)2CH2C6H4NO2, CF3CO2; (v) 4-FC6H4CH2Co(dotnH)B, where dotnH is the conjugate base of 4,8-diaza-3,9-dimethylundeca-3,8-diene-2,10-dione dioxime and B = CF3CO2, CN; (vi) 4-FC6H4CH2Co(dotnH)B+, where B = aq, py, Ph3P; have been prepared and isolated and/or characterised in solution. The fluorine-19 spectra have been measured and the substituent chemical shifts relative to that of fluorobenzene have been related to the electron-donating capacity of the substituent CH2Co(ligands). The electron-donating capacity of substituents of type (i) depend markedly upon the nature of the anionic ligand B, cyanide ion being particularly effective in promoting this electron donation. Cyanide ion is also very effective in the bridged cyanide complexes of types (ii) and (iii). Protonation of one of the dioximato-ligands of complexes of types (i), (ii), and (iii), or replacement of the two dioximato-ligands by the tetradentate ligand dotnH, more than outweighs the electron-donating influence of the monomeric or bridged cyanide ligand.

Substituent effects of (transition metallo)methyl groups by fluorine-19 nuclear magnetic resonance

A series of compounds of the general formula 3- and 4-FC6H4CH2MLmL′n where M is a transition metal have been synthesised and characterised. Ground state substituent effects of the metallomethyl groups CH2MLmL′n have been investigated by examination of the 19F substituent chemical shifts (SCS). The results indicate that whilst these metallomethyl groups produce net electron donation to the aromatic ring, the magnitude of the effect is strongly dependent on the metal and its attached ligands. The substituent effects in these ground states are markedly smaller than those previously detected in transition states and in studies of equilibria, but the order of electron-donating ability within the series of metallomethyl groups is the same for the ground states and for the transition states and equilibria. The results show that several neutral (carbonyl)metallomethyl substituents are as electron donating as the most effective main group metallomethyl substituents, but the electron-donating character of several neutral cobalt(III)-containing substituents is little different from that of the methyl group. The analogous rhodium(III) substituents are markedly more electron donating.