Sn groups

The H—NMR spectra indicate displacements of chemical shifts for the double bond protons of MA and TBSM and protons of the CH2—Sn group which suggest that two complex types are present in the mixture of the monomer pairs under study ... 

To determine the constant (Kc) of complex formation between TBSM and MA from the shifts of protons of anhydride, CH2 =, and CH2—Sn-groups, the modified Beneshi-Hildebrand equation 26) was used ... 

C6H5)3GeNCO shows no molecular ordering, unlike the corresponding tin compound which forms polymeric chains of planar [(CeHs Sn] groups linked by NCO bridges (158). 

A153. D. M. Adams, Metal-Ligand and Related Vibrations A Critical Survey of the Infrared and Raman Spectra of Metallic and Organometallic Compounds. Arnold, London, 1967. 360 pp. There are tabulated data and references on metal-carbon and related frequencies (especially on Zn, Al, Sn groups) and on metal-ligand frequencies involving heavier group VB and VIB donors. 

Scheme 1 JT symmetry descent paths of Oh parent group and its subgroups (upper lines in rectangles) for IRs (bottom lines in rectangles) Eg (a), Tig and Tgg (b). Analogous schemes may be obtained for ungerade IRs ( , Tiu, T2u) replacing subscripts g by the u ones where appropriate. For continuation see Schemes 2 Td and T groups), 4 Sn group) and 6 (Du and Dg groups)...

The Sn. groups have an S axis as their basis. This usually implies other symmetry operations. For example, an S4 implies a C2, and an S4 ( Sr ). 

Although symmetrically structured, ( )-l,2-bis(stamiyl)ethylenef can be either selectively monosubstituted or exhaustively disubstituted. The available results indicate that, like halogens, the second Sn group accelerates the Pd-catalyzed cross-coupling. Some very attractive applications of both (E)- and (Z)-l,2-bis(stannyl)ethylenes include their Pd-catalyzed double cross-coupling reactions with a,-diiodo compounds to prodnce macrocycles in the syntheses of rapamycin and dynemicin discussed in Sect, m.2.18. 

Organotin compounds are also active as catalysts in the polymerizations of A -carboxy anhydrides. " The mechanism of the reaction was postulated by Freireich, Gertner, and Zilkha " to consist of addition of the organotin compound to the anhydride and formation of organotin carbamate. It subsequently decarboxylates and leaves an active -N-Sn- group that adds to another molecule of A -carboxyanhydride. This process is repeated in every step of the propagation " ... 

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