5- Coordinate complexes species

Isomeric forms of Eu(III) complexes may give rise to multiple excitation peaks if the Eu(III) coordination sphere is sufficiently different. For example, Eu(TCMC) [refer to Fig. 8.5 for this and other Ln(macrocycle) stmctures] has two different diastereomeric forms in solution that result from distinct orientations of pendent groups and macrocyclic ring (Fig. 8.6) [44,45]. Note that the Ln(ni) complexes are specified without water ligands [e.g. Eu(TCMC)] unless a particular coordination complex species is discussed [e.g. Eu(TCMC)(OH2)]. 

Figure 8.5 Macrocydic lanthanide complexes discussed in this chapter. Ln(lll) complexes are specified without water ligands unless a particular coordination complex species is discussed...

Iron hahdes react with haHde salts to afford anionic haHde complexes. Because kon(III) is a hard acid, the complexes that it forms are most stable with F and decrease ki both coordination number and stabiHty with heavier haHdes. No stable F complexes are known. [FeF (H20)] is the predominant kon fluoride species ki aqueous solution. The [FeF ] ion can be prepared ki fused salts. Whereas six-coordinate [FeCy is known, four-coordinate complexes are favored for chloride. Salts of tetrahedral [FeCfy] can be isolated if large cations such as tetraphenfyarsonium or tetra alkylammonium are used. [FeBrJ is known but is thermally unstable and disproportionates to kon(II) and bromine. Complex anions of kon(II) hahdes are less common. [FeCfy] has been obtained from FeCfy by reaction with alkaH metal chlorides ki the melt or with tetraethyl ammonium chloride ki deoxygenated ethanol. 

The rhodium and iridium complexes of dibenzothiophene (L) reveal an interesting case of linkage isomerism (91IC5046). Thus, the ti S) coordinated species [MCp LCb] on thermolysis with silver tetrafluoroborate afford the Ti -coordinated dicationic species. 

The same lithium salts with copper(I) chloride react through the stage of the anionic C-coordinated complexes 100, which on protonation with hydrochloric acid give the corresponding 2,2 -bithiazoles, with triflic acid— the N-coordinated species 101, and on methylation with methyl triflate they give carbenes of structure 102. 

The only reports of directed synthesis of coordination complexes in ionic liquids are from oxo-exchange chemistry. Exposure of chloroaluminate ionic liquids to water results in the formation of a variety of aluminium oxo- and hydroxo-contain-ing species [4]. Dissolution of metals more oxophilic than aluminium will generate metal oxohalide species. FFussey et al. have used phosgene (COCI2) to deoxochlori-nate [NbOa5] - (Scheme 6.1-1) [5]. 

The products obtained from the Pt(PR3)2X2-CNCH3 reactions were dependent on the nature of the platinum species. Five-coordinate adducts, [Pt(PR3)2(CNCH3)2X]X, were isolated for the iodo and bromo complexes (R=Ph), although the latter was unstable and slowly lost isocyanide. The observation of five-coordination here is somewhat unusual, but since this report, it was also observed in a different situation (85), mentioned above. The more common observation was the isolation of four-coordinate species, implying the low stability of most five-coordinate complexes. Data on these reactions are summarized below [Eqs. (33, 34)]. 

Treichel, Knebel, and Hess provided further data on these systems by studying reactions of [Pt(PRj)2(CNCH3)2] with various halide ions and with pseudohalides. A series of five-coordinate complexes were obtained from reactions with iodide ion (PRj = PPhj, PPh2Me, PPhMe2, PEtj), and a study was carried out to measure the stability of these complexes with respect to ligand loss 155). Stability constants for several of these complexes were obtained from spectroscopic data. Other reactants (Cl, Br, CN, SCN) generally yielded the appropriate [Pt(PRj)2(CNCH3)X] species, as expected. 

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