Macrocycles, organotin

There have been reports on four types of macrocyclic organotin(IV) assemblies formed from neutral or anionic bidentate organic connectors (i) mononuclear R4 Sn(IV) + macrocycles (ii) di- and oligonu-clear R4 Sn(IV) + macrocycles (iii) dinuclear cryptands and (iv) macrocycles and cryptands formed from oligonuclear secondary building blocks. 

Advances in techniques include sophisticated NMR methods, both in solution and the solid-state, and computational methods, and these, coupled with X-ray diffraction and other established methods, have been applied to the study of a wide variety of structures. Topics covered in the book include Sn(II) clusters, tin Zintl ions, Sn(II) heterobimetallic compounds, RsSn+ cations, stannylenes (R2Sn ), stannenes (R2Sn=SnR2 and R2Sn=CR2), stannynes (RSn=SnR), organotin oxide, carboxylate and sulfonate clusters, dendrimers and macrocycles, organotin polymers, Sh-tt interactions, unusual bondings and structures, and compounds with non-linear optical properties. 

Various organotin reagents react with acyl and aroyl halides under mild conditions without decarbonylation to give carbonyl compounds[390,39l]. Alkyl- or alkenyltin reagents react with acyl and aroyl chlorides to give ketones[548.733,734]. One example is the preparation of the a,/3-dnsaturated 7-keto esters 860 and 861, carried out under a CO atmosphere[735]. The reaction has been applied intramolecularly to the synthesis of the macrocyclic keto... 

Intramolecular Pd(0)-catalyzed Stille reaction of organotin reagents with electrophiles leading to C—C a-bond formation in synthesis of heterocycles, particularly, macrocyclic lactones 99JCS(P1)1235. 

One example of a tin porphycene has been reported, but as yet no organometallic derivatives have been reported." A small number of tin corrole complexes are known including one organotin example, Sn(OEC)Ph, prepared from the reaction of Sn(OEC)Cl with PhMgBr. A crystal structure of Sn(OEC)Ph shows it to have both shorter Sn—N and Sn—C bonds than Sn(TPP)Ph2, with the tin atom displaced 0.722 A above the N4 plane of the domed macrocycle (Fig. 6). The complex undergoes reversible one-electron electrochemical oxidation and reduction at the corrole ring, and also two further ring oxidations which have no counterpart in tin porphyrin complexes. " " ... 

A very unusual mixed-metal receptor has been prepared by Jurkschat and co-workers [68]. Macrocycle 102 comprises two ferrocene reporter units linked together by two Lewis acidic organotin spacers. Electrochemical measurements in dichloromethane solution show anion-induced cathodic shifts of the ferrocene/ferrocenium redox couple of 130 mV for chloride, 210 mV for fluoride and 480 mV for dihydrogenphosphate. 

Carbonylative coupling of vinyl triflates with organotins (12, 470-471).3 The final step in a synthesis of the macrocyclic diterpene jatrophone (2) was effected by carbonylative coupling of a vinyl triflate with vinyltin catalyzed by bis(acetonitrile)-dichloropalladium. 

The preparation and use of organotin compounds as re-polymerization agents for linear polyesters and macrocyclic oligomers is provided by Paler [1] and Winckler [2], respectively. 

Bis(trimethyltin)malonate, Me3SnOOCCH2COOSnMe3 (127), is an intriguing example of a three-dimensional network built up by pentacoordinated organotin moieties with the oxygens in the axial positions of a trigonal bipyramid [Sn—O 2.19(1), 2.17(1), 2.44(2), 2.46(2) A] and malonate units as tetradentate spacers . The basic three-dimensional structure consists of four helices which are interconnected by O—Sn—O bridges resulting in 24-membered macrocycles. 

Scheme 8 Tetrameric and hexameric organotin self-assembled macrocyclic supermolecules...

Newcomb s group has developed MM2 parameters for organotin compounds. The parameters were based on IR, ab initio, and crystal structure data. They developed these parameters so that they could treat the following Lewis acidic macrocyclic hosts.It was found that the experimental structures were well reproduced. The major deviations from the crystal structure came from regions with a high disorder. 

The total synthesis of protected enterobactin 10, developed by Shanzer and Libman [14 a], involves the use of organotin species as templates in the cyclooligomerization of ff-lactones to macrocyclic polylactones (Scheme 2) [14 b]. The [Bu2Sn(OCH2CH20)]2 acts like a homogeneous catalyst in this reaction. 

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. ... 

Organotin Carboxylate and Sulfonate Clusters 101 Table 2.4.2 Representative examples of trinuclear diorganostannoxane macrocycles... 

The purpose of the present survey is to examine and visualize the potential that organotin(IV) complexes can have in metal-directed self-assembly of macrocycles and extended networks. Their application in the formation of cage- and cluster-type structures is only mentioned superficially, since this chemistry is described in other sections within this chapter. 

Considering that the formation of metallocyclic polygons and polyhedra requires at least two free coordination sites, the number of possible bonding environments is limited. Figure 2.5.2 summarizes the coordination geometries found most frequently in organotin(IV) macrocycles and coordination polymers. 

Dicarboxylates or carboxylates containing an additional anionic function (e.g. RS , RO, etc.) capable of coordination to tin atoms (functionalized monocarboxylates) are ideal candidates for the constmction of discrete di- and oligonuclear organotin macrocycles, as is shown by a series of organotin carboxylate macrocycles having dimeric, trimeric, tetrameric, and hexameric compositions (Figure 2.5.11). 

The tetranuclear macrocycle shown in Figure 2.5.11c has been obtained by a very interesting and promising synthetic strategy, which consists of the application of a functionalized organotin complex in the self-assembly process. ... 

Figure 2.5.11 Di-, tri-, tetra- and hexanuclear macrocycles can be prepared from carboxylate-derived connectors using (a) dicarboxylates (b) functionalized monocarboxylates and (c) organotin compounds functionalized with a carboxyl ate group...

Figure 2.5.12 Organotin macrocycles derived from bis(dithiocarbamates) as organic connectors...

Figure 2.5.74 Representative examples for oligonuclear (a) macrocycles and (b) cryptands that have been prepared from ladder-type secondary organotin building blocks linked through organic and/or inorganic connectors...

It has been reported that subjection of an 11-membered macrocycle involving an alkyne and alkenes to a radical cyclization procedure leads to a tandem cyclization giving rise to the formation of a fused 6,7-bicychc framework [249]. It should be mentioned that the in situ methodology for generation of organotin hydride works... 

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