Isomers polymerization

Magnus s salt is an electrolyte and non-ionized polymerization isomers (p. 921) of the stoichiometry PtCl2(NH3)2 are also known which can be prepared as monomeric cis and Irons isomers ... 

Green Salt. The two salts are also so-called polymerization isomers of the cis and trans isomers of the dichlorodiammine complexes of the corresponding metals, which for platinum are cis- and fra/2s-[PtCl2(NH3)2] (see Section 1.1.2.8). 

The possibility that the compounds might be polymerization isomers has been eliminated by cryoscopic determinations of molecular weights in benzene solution, which showed both isomers to be monomolecular. Dipole moments in such solutions were found to be 9.5 D. for the cis isomer and 2.41 D. for the trans isomer. The latter is not zero since the four ethyl groups lie on the same side of the plane containing the platinum, chlorine, and sulfur atoms. Interconversion of the isomers does not occur read-... 

The compounds Co(NH3)t>Cr(CN)8 and Cr(NH3)6Co(CN)6 are termed coordination isomers. The first contains Co— N and Cr—C bonds whereas the second contains Cr—N and Co—C bonds. There are four additional coordination isomers related to these two compounds (Exercise 2). Pairs of compounds such as PtCI2(NH3)2 and Pt(NH )4+PtCl are sometimes called polymerization isomers, but may just as logically be regarded as coordination isomers in which both centers of coordination hold the same atom. 

Again, the metal-carbon stretching frequencies are markedly different in these two hexacyano complex ions. It is, therefore, relatively easy to differentiate coordination isomers such as fCo(NH3)6] [Cr(CN)6] and [Cr(NH3)6] [Co(CN)6]. Coordination isomers involving the same central metal may be more difficult to identify from their infrared spectra. Thus, [Pt(NH3)4] [PtClJ and [Pt(NH3)3Cl] [Pt(NH3)Cl3] may exhibit very similar spectra. This is also expected for polymerization isomers such as [Co(NH3)3(N02)3] and [Co(NH3)e] [Co(N02)e] because the central metal is the same in both compounds. However, minor differences may possibly be seen in the far-infrared region where the skeletal vibrations of these complexes appear. 

Figure 51 The structure of a second polymeric isomer of [Sbslio] (reproduced by permission of Wiley-VCH from Angew. Chem., Int. Ed. Engl. 1986, 25, 825).

Polymerization isomers the complexes exemplified have identical empirical formulae but differ in the number of replications of the empirical formula, Pt CbfNI I3 h . 

Polymerization isomers denote complexes which have the... 

Polymerization isomers. In the case of octahedral complexes, formula [MX BJn, polymerization isomers are often possible. The value of n is greater than or equal to 1. Several compounds of empirical formula [Co(NH3)3(N02)3] can be isolated. 

Note added in proof A recent study of dipole moment, electrophoretic behavior, conductance, n.m.r. and absorption spectra, and derivative formation by G. B. Kauffman, J. H. Tsai, R. M. Kallo, R. C. Fay, and C. K. J0rgensen has demonstrated conclusively that while the yellow isomer is indeed cis, the red compound is an electrolytic polymerization isomer, irans-[Ir ((C2H6)2S) 4CI2] fra s-[Ir (C2Ht)2S) 2CI4I. 

The combination of a linear bifunctional telechelic precursor with a tricarboxylate counteranion produced a self-assembly that consisted of three polymer units and two counteranions under dilution. Subsequent heat treatment produced a pair of covalently fixed constitutional isomers, namely manacle-shaped and 0-shaped polymers (Scheme 18.3b) [6, 15]. These relevant pairs of polymeric isomers were formed from a self-assembly of two units of a three-armed star telechelic precursor and three units of a dicarboxylate counteranion [16], as well as from the double-metathesis condensation of an H-shaped telechehc polymer precursor having four alkene end groups (Scheme 18.3c) [17]. 

Strictly speaking, polymerization isomerism, in which n varies in the complex [ML ] (the Ls need not all be identical), is not isomerism. It is included in this list because it represents an additional way in which an empirical formula may give incomplete information about the nature of complex. For example, all members of the following series are polymerization isomers of [Co(NH3)3(N02)3] . 

Scheme 1.11 Synthesis of topological polymeric isomers having manacle- and 0-shaped constructions by the ESA-CF process (Oike et al, 2000 Tezuka et al 2003b).

Scheme 1.12 Synthesis of manacle- and 0-shaped topological polymeric isomers through the double metathesis of an H-shaped prepolymer (Tezuka and Ohashi, 2005).

---