Structure triorganotin carboxylates

The tin-oxygen interatomic distances present in organotin carboxylates were classified in terms of primary Sn—O covalent bonds ca 2.0 A), slightly longer dative Sn—O bonds (ca 2.2-2.3 A) and Sn- -O secondary interactions (>2.5 A)214. Triorganotin carboxylates can adopt the three idealised structure types 124a-c. 

In the crystalline state, triorganotin carboxylates generally adopt either a polymeric structure with a five-coordinated tin atom (type 383) or a monomeric structure varying from a purely tetrahedral four-coordinate geometry (type 384) to a similar one with a weak additional intramolecular coordination from the carbonyl oxygen to the tin atom (type 385)107,266,778.779... 

Among organotin carboxylates, clusters and cages are formed mainly in di- and monoorganotin compounds. Among triorganotin carboxylates, the predominant structures are chain and discrete structures, although some macrocycles are also known. ... 

Triorganotin carboxylates, R3Sn02CR, formed generally in the reactions of RsSnOH or (R3Sn)20 with a carboxylic acid R C02H, usually possess two main types of structures (a) chain structures (b) discrete structures. 

Polymeric or chain structures are the most common stmctural types known for triorganotin carboxylates. These are formed in three situations (Figure 2.4.1) ... 

Figure 2.4.2 Representative examples of various structural forms of triorganotin carboxylates (a)-(c) represent discrete structures (d) represents a chain structure where the carboxylate ligand bridges two tin centers (e) represents a chain structure where a heteroatom and a carboxylate ligand bridge two tin centers (f) represents a dimeric structure and (g)-(h) represent macrocyclic structures.

A selection of structurally characterized triorganotin carboxylates is listed in Table 3.13, in order of complexity of the organic groups at tin. The Sn-O and Sn O bond lengths and O-Sn O axial bond angles are given. 

Some triorganotin carboxylate structures, in particular those containing two RsSn moieties, deserve additional comment because their structures are more varied. For example, rare types of organotin carboxylates include derivatives of carborane-carboxylic acids [ (l,7-C2BioHn-l-COO)Bu2Sn 20]2 (structure of type A) [451]. The bis(triphenyltin) derivative of phenylmaleic acid, 145, contains only four-coordinate tetrahedral tin (Sn O 2.077 and 2.090 A) and is not associated, but in the bis(triphenyltin) citraconate, 146, one tin atom participates in the supramolecular association, 147, and polymer-chain formation and becomes five-coordinate (trigonal pyramidal Sn-O 2.193 A, Sn O 2.397 A) whereas the second remains four-coordinate (Sn-O 2.089 A), as a part of a dangling side chain [441]. 

Diphenic acid (H2A) also forms diorganotin(IV) complexes, which are with two monodentate -COO groups. On the other hand, soluble dinuclear triorganotin(IV) complexes (where the organo moieties are Me and Ph) contain symmetrically bound carboxylates, while the less-soluble compound (cHexsSn) has two asymmetrically bonded carboxylates. All have Tbp structures with [RsSnirV)] units remote from each other. °... 

The first systematic studies of structure-activity relationships in anti-tumor organotins were carried out by Gielen s group, on several di- and triorganotin(IV) carboxylates, including 2,3-pyridinecarboxylates (Figure 4.4.1), and their cytotoxicity. ... 

Figure 21 Generic chemical structure for triorganotin 2-[(E)-2-(2-hydroxy-5-methylphenyl)-l-diazenyl]benzoates. The hydroxyl group forms an intramolecular hydrogen bond to the anazo nitrogen atom and does not participate in intermolecular interactions of note. The rotation about the 0-C-carboxylate bond allows for the formation of either intra- or intermolecular Sn- -O interactions.

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