Complexes of Tin

The situation in the cyclopentadienyl chemistry of tin is similar to that described for germanium several classes of cyclopentadienyl compounds are now known. The first compound in this series was reported by Fischer and 

Cp (Me3Sn)H4C5 [(/-Pr)2N]2PH—H4C5 Ph5C5 (MeCO)H4C5 (MeOCO)H4C5 (EtOCO)H4C5 

Cp (Me3Sn)H4C5 H5CJAlCli H5C5 H5C5 H5C5 H3C5 

The distorted pentahapto attachment of the cyclopentadienyl rings in bent stannocenes is not reflected in their low-temperature H- or 13C-NMR spectra, where only averaged resonance signals are observed. The barrier for 

The tin-119m Mossbauer spectra of some stannocenes were recorded by Zuckerman s group (221,222). The observed isomer shifts are compatible with the presence of divalent tin, while the dependence of the quadrupole splitting on the interplanar angle in these complexes is still unknown. 

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Another type of demasking involves formation of new complexes or other compounds that are more stable than the masked species. For example, boric acid is used to demask fluoride complexes of tin(IV) and molybdenum(VI). Formaldehyde is often used to remove the masking action of cyanide ions by converting the masking agent to a nonreacting species through the reaction ... 

Interesting new sulfido complexes of tin have been prepared by the reaction of styrene sulfide with the N-alkylated tin(II) amidinate complexes Sn[RC(NCy)2]2 (Cy = cyclohexyl R = Me, Bu ). The products exhibit two very different bonding modes for the sulfido ligands in one case, S = Sn[RC(NCy)2]2/ a terminal Sn = S moiety was found while in the other case the bridging... 

Alumina is known to have more ionic character and its surface has a more complex structure than that of silica. Reaction of Bu3SnH with the surface of partially dehydroxylated aluminas was followed and it was found that the extreme sensitivity of tin chemical shifts to the molecular environment constitutes a method whereby surface organometallic complexes of tin can be used as molecular probes for determining surface structures of oxides.248... 

Similarly, stannanethione 125 and stannaneselone 127 kinetically stabilized by Tbt and Ditp groups have 119Sn chemical shifts of 531 and 440 ppm, respectively. Recently, Parkin et al. have reported the synthesis of stable terminal chalcogenido complexes of tin 150 (Scheme 38), and the chemical shifts for the central tin atom... 

There are only a few examples of complexes of tin(II) and lead(II)81,82. Figure 10 shows [B(Pz)4]2Sn where the tin atom is four-coordinated in the solid state, adopting a pseudo-trigonal bipyramidal structure with the lone pair of the tin(II) in the equatorial position. The analogous lead complex has also been described83. 

Of more interest to coordination chemists is the Du Pont halogen tin process which is based on halo complexes of tin(II). The presence of fluoride is considered to form [SnF3], but much chloride is present to enhance the conductivity. Inhibitors are required to control the oxidation of tin(II) to tin(IV) and the consequent separation of the sparingly soluble Na2[SnF6] as a sludge. The process was originally introduced in 1942 for the continuous electrotinning of steel strip. 

Excess benzyl bromide and triethylamine in the presence of tin(II)chloride catalyst were used [91] for partial benzylation of methyl a-L-rhamnopyranoside and its 4-O-benzyl ether. Complexation of tin(II)chloride with vicinal m-disposed hydroxyl groups permitted selective benzylation at the 3- and 2-positions. Methyl 3-O-benzyl-or 3,4-di-O-benzyl-a-L-rhamnopyranoside, respectively, could be prepared in good yield by this method. No benzylation took place when benzyl chloride was used instead of benzyl bromide, or when other solvents than ethyl acetate or acetonitrile were tested. 

The application of NMR to a study of the structure and complexation of tin compounds was reported by us at the 11th European Conference on Molecular Spectroscopy (114)- In the present review we would like to emphasize that a study of electronic and spatial structures of methyltin halides requires, in the first place, a study of spin-spin coupling between noSn and H and 13C in methyl groups. 

Kinetic TBDMS enol ethers were isomerized to the thermodynamic ethers in the presence of catalytic amounts of the coordinate complexes of tin tetrachloride and the monoalkyl ethers of BINOL or biphenol, whereas the use of the coordinate complexes with biphenol and other monoaryl alcohols predominantly afforded the corre-... 

Novel catalyst compositions comprising complexes of tin(IV) salts and primary amine compounds allow delay of gelation until they dissociate under certain reaction conditions. Encapsulated catalysts have been used for delayed reaction in production of explosives this delay permits casting of explosives. 

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