Homoleptic compounds

The use of homoleptic compounds, where all coordinating atoms are as chemically indistinguishable as possible. Indeed, with heteroleptic complexes it can easily be the case that the error in the parameterization of the effect of a type of ligand can be compensated and thus shadowed by another error in the parameterization of a different ligand, resulting in flawed parameters for both of them. 

Figure 2.8 Average radius Rav and effective or trispyrazole [22], oxygen atoms of the charge Zf resulting from the REC correction POM series LnW10 and LnW22, [23] and halo-of different homoleptic compounds nitro- genides F , Cl-, Br" anions [21]. genated ligands of the type bis-pyrazole...

The degradation of a compound in TFIF-rfs solution could be followed by 3 P H NMR spectroscopy. Thus, for example, the heteroleptic dimeric phosphanide Grignard analogue 77 does not dissolve well in nondonor solvents the fresh solution in TFIF shows two main peaks A and B, at 5—107.0 and —103.1 ppm, respectively peak B is tentatively attributed to the homoleptic compound 78, obtained on loss of MgBu2. After 1 h, peak A is markedly... 

The title ligands are the monoanionic 6-10 and the dianionic 11 and 12. Doubly deprotonated diazacrowns have also featured in Ln " chemistry, as well as A,A -dianionic macrocycles. Exceptionally, an [N(H)aryl] ligand figured as a chelate, implicating the aryl 7i-electrons, as in 2. ° Structurally characterised complexes using these ligands included [Nd(6)3], Li[Ho(7)4] (the homoleptic compound was not accessible from H0CI3 I Li N-... 

There do not appear to be any structural characterizations of homoleptic compounds of this class. However, the simple fusing of two tetrahedral units most probably occurs for [Al(NMe2)3]2 as is seen... 

In order to highlight the major aspects of the physical and spectroscopic properties of metal alkoxides and phenoxides, representative examples of homoleptic compounds of stoichiometries M(OR)v or M(OAr)x will be considered. 

In the case of the alkoxides and phenoxides of molybdenum(III) the interaction between metal atoms becomes dominant, leading to diamagnetic compounds of stoichiometry Mo2(OR)6 or Mo4(OR )i2(R/ = the less bulky Me or Et).78 These compounds are readily sublimable, (70-90 °C/ 10-3 Torr for Mo OPr1 ) and retain either their dimeric or tetrameric nature both in solution and the gas phase, as determined by cryoscopic measurements and mass spectrometry, respectively.78 An analogous tungsten(III) complex W2(OBu )6 can be obtained, but for other alkoxides the simple homoleptic compounds cannot be isolated.79,168... 

The introduction of the btsa ligand into lanthanide chemistry by Bradley led to the isolation of the homoleptic compounds Ln(btsa)3 [7], interpreted as the first 3-coordinate lanthanide complexes. This result was indeed spectacular and exploration of the chemical and physical properties of this simple system is continuing [104-106]. 

Only homoleptic compounds are considered here, compounds bearing miscellaneous ligands including elements of Group 15 to 17 are discussed in Section V. Several inorganic compounds such as Al7Te10, GaS, or In6Se7... 

Some tr-alkyl and aryl compounds have been made with supporting ligands such as Cp, Cp, bulky aryloxides such as o -Bu QHjO,56 and tertiary phosphines, as exemplified by Cp UCH(SiMe3)257 and UR dmpe. Homoleptic compounds have proved more difficult to make. There are, however, the compounds Th(CH2Ph)4, ato complexes [Li tmed]3[MMe7], M = Th, U, and the blue U[CH(SiMe3)2]3 which is stable as the solid at -60°C though unstable in solution over a few hours.58... 

The homoleptic carbonyl (see Homoleptic Compound) Co3(CO)9 is not known, but a few substituted derivatives have appeared in the literature. The best characterized cluster seems to be Co3(CO)9H, which is found in 10% yield as a decarbonylation product of Co3(CO)ioH ([CosCJOH). The X-ray structure has disclosed a regular triangle with three bridging and six terminal CO groups. The hydrogen atom was not located in the diffraction study. 

Only one example is known of a binary homoleptic (see Homoleptic Compound) cobalt alkyl compound, Co(nb)4... 

This remarkable species is one of the very few homoleptic transition metal hydrides see Homoleptic Compound). The... 

Reaction of R2ln-InR2 (R = CH(SiMe3)2) with the chalcogen compounds can give the corresponding homoleptic compounds R2lnEInR2 (E = S, Se or Te) by insertion of... 

For a noncubic complex, we need at least two parameters to describe the LF splitting. In the case of a homoleptic complex ML (see Homoleptic Compound), where all M-L distances r are equal, the simple CF description - requires two parameters, ai and 04, which are proportional to r and respectively. A less regular complex requires more than two parameters. For example, the d-orbital splitting in regular square planar CuCU can be written in terms of just two parameters. For trigonal bipyramidal CuCls ", where the axial and equatorial Cu-Cl distances are unequal, we still need just two parameters, because a2(eq) and a2(ax), and a4(eq) and fl4(ax), are related by their respective and rdependence. 

Pure phosphine-metal atom studies with the early transition metals have been lacking. The only complex prepared this way prior to 1978 was Cr(Pp3)6. King and Chang, with the unique aminophosphine systems Me2NPF2 and MeN(Pp2)2, have generated a variety of new homoleptic M-(L) systems (see Homoleptic Compound). The codeposition of Cr vapor with these ligands yields the complexes shown ... 

The macroscale codeposition of PF3 has yielded a series of M-PF3 complexes. Some of these M-PF3 complexes can only be prepared by the metal vapor-ligand cocondensation technique. Very electron-rich M-phosphine and M-phosphite derivatives have been prepared by M-PMe3 and M-P(OMe)3 depositions, as shown in Table 8. A series of new homoleptic compounds have been prepared. Cocondensation of Fe and Ni with some arene systems gives stable (Ar)2Fe/Ni species, if maintained at low temperatures. 

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