Tris homoleptic structures

There are nine homoleptic tris(dithiolene) structures reported in the CSDC based on main group elements, specifically Sn, Sb, and In. The elemental distribution is shown in Fig. 15 and a detailed listing of the structures is given in Table V. 

Reactions of UCI4 with [Li RC(NCy)2 (THF)]2 (R = Me, Bu ) in THF gave the tris(amidinate) compounds [RC(NCy)2]3UCl that could be reduced with lithium powder in THF to the dark-green homoleptic uranium(lll) complexes [RC(NCy)2]3U. Comparison of the crystal structure of [MeC(NCy)2]3U with those of the lanthanide analog showed that the average U-N distance is shorter than expected from a purely ionic bonding model. ... 

Homoleptic complexes have been obtained also with tetrakis(l-pyrazolyl)borates, e.g., [ B(pz)4 2Cd] and [ B(3-Mepz)4 2Cd] (both P2 jc, Z = 2) in both compounds structure analyses the ligands have been shown to coordinate trihapto, i.e., with one pz ring free. In both cases Cd has a distorted octahedral environment, with averaged structural data very similar to those for the tris(l-pyrazolylhydridoborate complexes.201 Variable-temperature 3H NMR studies of these and of mixed complexes with tris- and bis(l-pyrazolylhydridoborates indicate fluxional behavior (coalescence temperatures and barriers for the dynamic processes are given). 

Let us pass now to the wider class of homoleptic (tris)quinoidal complexes (already mentioned in Chapter 5, Section 1, speaking about the redox couple [V(cat)3]2 /3 ) starting with the neutral complex [Cr 02C6H2(3,S-Bu h], the essentially octahedral structure of which is shown in Figure 32.54... 

The homoleptic lanthanide(III) benzamidinates 20-23 can be regarded as analogues of the well known tris(cyclopentadienyl)lanthanide complexes (C5H5)3Ln [7, 8]. One of the most characteristic reactions of the homoleptic cyclopentadienyls is the formation of 1 1 adducts with Lewis bases such as ethers, nitriles, esters etc. [7, 8], Recently it was discovered that the homoleptic lanthanide benzamidinates [PhC(NSiMe3)2]3Ln (20) form similar adducts with THF and nitrile ligands such as acetonitrile or benzonitrile [59]. The molecular and crystal structures of two benzonitrile adducts (26g, h) have been determined by X-ray diffraction. Figure 8 depicts the molecular structure of the europium... 

Structural evidence of the formation of alkylated siloxide complexes was obtained from the reaction of homoleptic tetramethylaluminates Ln(AlMe4)3 with one equivalent of tris(ferf.butoxy)silanol HOSi(Of-Bu)3. This fast protonolysis reaction results in heterobimetallic Ln/Al complexes Ln[OSi(Of-Bu)3](AlMe4)2(AlMe3) (Ln = Y, Ce, Pr, Nd, La) via quantitative... 

There are roughly 50 homoleptic tris (dithiolene) complexes reported in the CSDC (5). The elemental distribution of these structures is outlined in Fig. 15. As opposed to bis(dithiolene) complexes, tris(dithiolene) complexes are based predominantly on early transition metal elements. Many of the tris(dithiolene) complexes are centered on V, Mo, and W. There are also complexes of Ti, Zr, Nb, Ta, Cr, Tc, Re, Ru, and Os. In addition, there are tris(dithiolene) complexes of Fe and Co, elements that also form homoleptic complexes with two dithiolene ligands. A detailed listing of the structural units along with references and geometrical parameters (to be discussed) is given in Table IV. 

Average bond length and angle parameters for the homoleptic tris(dithiolene) complexes are less sensitive to the identity of the transition metal or dithiolene ligand than those of bis(dithiolene) structures. Ranges of values are summarized in Fig. 22. Average M—S bond lengths cluster between 2.263 and 2.543 A, with values for two [Fe(mnt)3]2 units (2.263 and 2.269 A) (18), Co CAlCO),, 3... 

Except for the homoleptic bi(porphyrinato) and tri(porphyrinato) rare earth complexes, complexes with different porphyrin macrocycles were also investigated. To date, some sandwich type heteroleptic bis(porphyrinato) rare earth double-deckers have been synthesized. However, few have been structurally characterized via single crystal X-ray diffraction analysis [47]. Among these, Ce(IV)(OEP)(TPP) is the only structurally characterized neutral heteroleptic bis(porphyrinato) rare earth double-decker complex [48]. Using an improved short route, Coutsolelos and coworkers prepared and isolated a series of heteroleptic bis(porphyrinato)... 

Whereas complexes of unsubstituted and substituted cyclopentadienyl ligands represent the vast majority of all published compounds in organolanthanide chemistry, examples of isolated and fully characterized (including X-ray structural analyses) compounds containing only cr-bonded alkyl and aryl ligands are still fairly rare. The first structurally characterized homoleptic lanthanide alkyls became available through the use of bulky mono-, bis-, and tris(trimethyl-silyl)-substituted methyl ligands. Simple unsolvated alkyls of the rare earth elements have not yet been synthesized. 

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