Homoleptic species

Hydroc rbylComplexes. Stable homoleptic and heteroleptic thorium hydrocarbyl complexes have been synthesized. Two common homoleptic species are [Li-TMEDA]2 Th(CH2). ] [92366-18-2] (19), where TMEDA = tetramethyl ethylenediarnine, and Th(CH2CgH ) [54008-63-8] (20). 

Fig. 17. Difference in cis and trans Pt-Cl bond lengths in [PtnCl3Y] (in purple) and change in Pt-Y bond length in [PtnCl3Y] compared to the homoleptic species [PtnY4] (green).

The LFMM FF for the oxidized Cu(II) centers was designed around suitable homoleptic species, viz., [Cu(imidazole)4]2+, [Cu(SCH3)4]2-, [Cu(S(CH3)2)4]2+, and [Cu(0=CH2)4]2+ (37). These complexes represent models for Cu-histidine, Cu-cysteine, Cu-methionine, and Cu-glutamine O/peptide respectively. Only the first of these species is known experimentally. However, it is amply documented that DFT gives excellent structures for metal complexes (64,65) so we can access the remaining species computationally (Fig. 20). 

Homoleptic species have been described in which the central atom is bonded to a... 

An additional aspect of the literature since 1980 has been an increasing interest in the characterization of charged amido complexes. In 1980 none had been strucmrally characterized. Several anionic complexes, including, for example, the homoleptic species [Na(thf)2Ti N(C6F5)2 4l [Na(thf)6]2[Zr(Ti -NC4H4)6], [ U(thf) 2Zr(NMe2)6] [ Li... 

The most important result of the structure studies was undoubtedly the establishment of the fact that the crystalline isopropoxides of all rare earths are not the homoleptic Ln(OPr )3 complexes but oxoalkoxides of Ln50(0Pri)13 composition, where Ln = Sc, Y, Er, Yb (see also Fig. 4.9 a). They appear to be desolvation products of the very unstable [Ln(OPri)3( PrOH)]2 solvates (perfectly soluble and rather reactive) the complex of such composition has been isolated and characterized only for neodymium, but the IR spectroscopic evidence for the existence of such solvates was obtained also for Pr and Er. Desolvation of Ln(OBu )3 2L (Ln = Y, La L = BuOH, THF, Py) leads also to the formation of oxocomplexes the ions corresponding to the fragmentation of the homoleptic species are absent in their mass-spectra (except for [Y3(OBu,)9(tBuOH)2], where the Y3(OR)8+ ion was found along with Y30(0R)6+). The same kind transformations have been observed also for... 

These rarely produce homoleptic species, but boron trialkyls can be obtained from diborane ... 

Okuda and Arnold have reported a series of 5- and 6-coordinate chiral indium complexes (e.g. 12), analogous to those previously discussed with yttrium (Table 4), which show varying activities for the polymerization of rac-lactide [71]. The homoleptic species was fluxional, interconverting between a 5-coordinate and fac- and mer-isomers of a 6-coordinate complex. It resulted in controlled polymerization and some stereoselectivity (max. P, = 0.63 and max. Ps = 0.64). MALDI-ToF mass spectrometry confirmed that the chiral alkoxide ligand was an initiating group. 

Apart from the heteroleptic plumbylenes 43a,b, one homoleptic species is known to form intramolecular N — Pb contacts bis-l-[2-(A,A/-dimethylaminoethyl)ferrocenyl] plumbylene (50)53, the Pb—N distances in 50 with 266.1 and 270.8 pm being again much longer than covalent Pb11—N bonds (ca 220 pm) or the Pb—N bonds in the plumbylene 43a (234.4 232.2 pm). 

These are metal compounds that have 3 to 9 hydrogen atoms which may be neutral, cationic, or anionic. They usually have tertiary phosphines or 7 -C5H5 as ligands but some homoleptic species are known. Some examples are given in Table 2-8. 

A variety of types are known. These may be homoleptic, such as Th(2,6-Bu C6H30)4, or mixed ligand as in Th(OBu )4py2 or Th(OAr)[N(SiMe3)2]3. The homoleptic species show a propensity for giving dimers, tetramers, and more complicated species, especially for smaller alkoxides like OMe. Bulky alkoxides or aryloxides are likely to give monomers or dimers as in the equilibrium for R = CHPr. 8... 

Singly bridged complexes are less numerous than doubly bridged ones. Representative examples are the homoleptic species [M(pz )] [M = Cu(I), Ag(I), and Au(I)]. Notably, the number of these binary complexes increased in the last years as well as their X-ray crystal structures (13). 

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