Mononuclear compounds table

The E-ligand bond lengths, including those for bulky ligands, match those found in simple mononuclear compounds (Tables 2 and 3). The E—E bond lengths may be compared with values for tetrahedral E in the elements (pm) ... 

In mononuclear and polynuclear Au(CgF5)3 compounds (Tables 3.12 and 3.13 respectively) the Au-C Fs bond lengths in the fragments mutually in trans position are in the same range and the remaining Au(C6F5) displays different distances depending... 

The simplest names for mononuclear compounds list the ligands followed by the name of the central atom and indicate only composition. The bonding of the ligand to the central atom can be indicated by the notations given in Section 3.2.3. The stereochemistry of mononuclear compounds can be given by the notation developed in Section 3.8. For examples see Tables 11, 12 and 13. 

In compositional nomenclature, ligands are given in alphabetical order before central atoms. Central atoms are listed in alphabetical order as well. Bridging ligands to the extent known are indicated by the p notation (see Section 3.2.3.4). The numbers of ligands and central atoms are indicated by the appropriate numerical prefixes (see Section 3.3.2). Anions, cations, oxidation states and ionic charges are indicated in the same manner as in mononuclear compounds (see Section 3.3.3). For examples see Table 14. 

Table 1. Typical mononuclear compounds of group 7 elements...

Chemistry involving transformations of the cyclopentadienyl (Cp) ligand itself will be discussed in Chapter 7 however, much of the chemistry of cyclopentadienyl complexes involves the ligand acting purely as a spectator. Thus there arises a broad area of chemistry involving complexes with both carbonyl and cyclopentadienyl ligands. The most common classes of such compounds (Table 3.4) are the mononuclear complexes... 

Table V represents the relationship betwenn half wave potentials and acidity for the binuclear complexes with a completely different sequence of protonated compounds. All of these structures are different from type I described above and they cannot be oxidized to the tin (IV) chelate without bond breaking and bond forming. This explains the higher stability of the binuclear chelates in acidic solution since their rates of oxidation are determined by the rates of rearrangement to the octahedral or pseudo-octahedral configuration (type I) of the mononuclear compound. Additional proof for this unsymmetric protonation sequence has been the isolation of several compounds which are presently being studied and one of which has been identified as H Y.SnCl, 2 H,0.

As discussed in the last section, the metal network in clusters may be considered, especially for high nuclearity clusters, as a finite portion of a compact metal structure stabilized by external ligands. The feature that the number of atoms is relatively small does not make the description of the system simpler. On the contrary, for pure metals as well as for traditional mononuclear compounds, there are theories which allow us to produce descriptions of their properties which, however, do not fit for clusters. In the very short history of this new class of compounds many efforts have been made to obtain some generalizations that permit us to rationalize experimental features as being structures and reactivity, as well as to perform quantitative theoretical calculations. The most important approaches to bonding in metal cluster are summarized in Table 2.8. 

The calculation based on the potentio-metric titration data of the Fe(III)-HEDP system indicates that the formation of mononuclear complexes (FeAH, FeA) is predominant (Fig. 9-9) (Kdlmdn et al., 1999). Furthermore, due to the high affinity of Fe " to hydrolyzation, the formation of mixed hy-droxo species [FeAOH, FeA(OH)2l is also significant (Table 9-4, model I). The quality of fitting is improved by assuming the formation of a dimeric (FeAOH)2 compound (Table 9-4, model II). A high percentage (>99%) of Fe " is linked to HEDP at pH >5. 

The robustness of the rhenium(i) diimine alkynyl systems and rich photophysical behavior have rendered them suitable as metalloligands for the synthesis of mixed-metal complexes. It is well-known that organometallic alkynes exhibit rich coordination chemistry with Cu(i), Ag(i) and Au(i) [214-218], however, photophysical properties of these r-coordinated compounds are rare. Recent work by Yam and coworkers has shown that luminescent mixed-metal alkynyl complexes could be synthesized by the metalloligand approach using the rhenium(i) diimine alkynyl complexes as the z -ligand. Reaction of the rhenium(i) diimine alkynyl complex [Re(bpy)(CO)3C=CPh] with [M(MeCN)4]PF6 in THF at room temperature in an inert atmosphere afforded mixed-metal Re(i)-Cu(i) or -Ag(i) alkynyl complexes (Scheme 10.31) [89]. Their photophysical properties have also been studied. These luminescent mixed-metal complexes were found to emit from their MLCT[d7i(Re) —> 7i (N N)] manifolds with emission bands blue-shifted relative to their mononuclear precursors (Table 10.5). This has been attributed to the stabilization of the dTi(Re) orbital as a consequence of the weaker t-donating ability of the alkynyl unit upon coordination to the d metal centers. 

A series of studies of cyclopentadienylmanganese tricarbonyl and related compounds has provided interesting results. As with the chromium compound mentioned above, it was found that carbonyl-rich compounds are formed in yields comparable to the retention. In these compounds, however, the yield of bi-nuclear Mn2(CO)io is not high, but mononuclear—Mn(CO)s compounds are prominent. The results are sumarized in Table 12. 

Table 3.12 Au-CeFs distances in mononuclear Au(C6F5)3 compounds.

TABLE 3.2.3 Suggested half-life classes of mononuclear aromatic hydrocarbons in various environmental compartments at 25 °C Air Water Soil Sediment Compound class class class class ... 

Mononuclear ER4 and simple four-coordinate compounds of E(IV) states are the baseline for viewing the other coordination numbers, the effect of bulky ligands, bonds to other E or metals, E(II) compounds, multiple bonds and other phenomena discussed in later sections. Basic parameters for some simple compounds are presented in Table 1, taken from the gas-phase data summarized by Molloy and Zuckerman5 and Haaland6. These data show the unperturbed molecules in the gas phase and provide the base for... 

We have previously seen examples of the carbon-like formulas of mononuclear and dinuclear osmium compounds, namely the methane-like tetrahydride (4.50c), ethylene-like H20s=CH2 (4.51c) and H2Os = OsH2 (Table 4.15), acetylenelike HOs = CH (4.54c) and HOs = OsH (Table 4.15), allene-like H2C = Os = CH2 (4.55a), and so forth. While the coordination numbers and Lewis-like formulas are formally analogous, the actual structures of Os and C species may be quite similar (e.g., the Td structures of OsfL and CH4) or dissimilar (e.g the strongly bent Cs structure of H20s = CH2 [Fig. 4.13(c)] versus the planar D2h structure of H2C = CH2). 

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