Trinuclear structures

A similar trinuclear structure has also been found in the carbonyl(piperidine-Af-carbonitrile)nickel(0) complex (37).189... 

Whereas Ni(acac)2(H20)2 has a mononuclear (raws octahedral structure,1536 the complex Ni(acac)2 has been found to possess a trinuclear structure (195) in which Ni06 octahedra share faces via bridging acac groups.1534 A reddish brown compound having the same stoichiometry has been extracted from a solution of Ni(acac)2 in CS2. It is assumed that the former compound contains both square planar and octahedral species in a 1 3 ratio.1550... 

The trinuclear structure of [Ni(acac)2]3 persists in solutions of non-donor solvents even at elevated temperatures, but is broken down by coordinating solvents, such as HaO, py, alcohols, and in general by the Lewis bases which give mono and bis adducts.1551,1552... 

Further condensation of the dinuclear species may occur either by continuing the edge-to-edge condensation, which leads to linear trinuclear structures such as 4a and 4b, or by condensation of a third chromium ion to each of the two chromium(III) centers in structure 2, yielding the cyclic structure 5. The (NH3)4Co(OH)2Co(CN)2(OH)2-Co(NH3)43+ cation (49) possesses structure 4a, and there is good evidence that the trinuclear amine complex Cr3(en)5(OH)45+ has the same structure (42). The linear trinuclear structure 4b has not been observed in crystal structures. The cyclic, trinuclear structure 5 has been observed in crystal structures of chromium(III) complexes with ammonia, tacn, and bispicam (40, 50, 51). 

Crystal data for the trinuclear (structure 5) and tetranuclear (structures 6, 7a, and 8) complexes reveal bond distances and angles which are comparable to those observed in the mono- and dihydroxo-bridged binuclear complexes (40, 42, 49, 50, 53, 54, 62, 87). 

It was established at the end of the 1960s [437,438] that the chelates of o-oxyazomethines and their analogues react with metal halides, forming bi- and trinuclear structures, for instance 750 and 751 ... 

The possibility that one of the products of the reaction between NbCls, C6Me6, Al, and AICI3 at 130 °C has a hexanuclear structure analogous to (Nb6Cl12)Cl (n = 2, 3, or 4) has been eliminated, at least for the solid state, by a single-crystal X-ray diffraction study529 which has shown it to have the trinuclear structure (59). 

It is soluble with decomposition in water, and forms stable, deep-red solutions in acetone, ethanol, and concentrated hydrochloric acid. Early molecular-weight determinations in glacial acetic acid indicated a dimeric structure,8 but recent molecular-weight studies in Sulfolane have definitely established the existence of the trinuclear structure. X-ray crystallography also shows a trimer.9 Re3Cl9 reacts with a number of ligands to form complexes of the type LsRe Cl , where L = triphenyl-phosphine, pyridine, etc.10... 

The initial product of the copper reaction is a brown precipitate of stoichiometry Cu(p-tol-NNNNN-tol-p)2, which, on heating, is reduced to deep red, air-stable Cu(p-tol-NNNNN-tol-p) j. The latter product, which is weakly paramagnetic [p ranges from 0.33 (113 K) to 1.52 BM (303 K)] and decomposes explosively at 160°C, has been found by X-ray diffraction methods to possess the trinuclear structure shown in Fig. 18. Three N, zig-zag chains coordinate three linearly arranged copper(I) ions through N-1, N-3, and N-5 atoms, such that each copper is in a trigonal-planar coordination environment. Mean copper-nitrogen distances are 2.036 A for the outer copper atoms and 1.945 A for the central copper atom. The copper-copper distances of 2.348 and 2.358 A are the shortest yet recorded for copper(I) complexes (6). 

Apart from relatively simple linear trinuclear structures such as that of the above [CpFe(CO)2]2Zn, Zn[Co(CO)4]2, [Fe(SiR3)(CO)3(PR3)CdBr]2, and related compounds with FeCd(/x-X)2CdFe and Fe—Cd—Fe groups,108 there are cyclic systems such as 15-XXII, 15-XXIII, and 15-XXIV, and a compound containing a Zn404 cubane core, [MeOZnFe(CO)2Cp]4. 

As a kind of extension of this particular type of trinuclear structure, there are numerous compounds that contain two such units fused together on a common edge to give either a discrete molecule as in W4(OEt)i6 (Fig. 16-23), and Mo408(OPr )4py4 or extended arrays of such a unit, joined by shared nonmetal atoms, as in MNb4Cln (Fig. 18-B-13) or certain mixed oxides of molybdenum such as Bai.i4Mo80i6. 

Among other trinuclear structures with a planar blocking ligand coordinated to the central metal ion are the cations [Cu tpa)]2[(Eg-tpp)Ee (CN)2] (66) and... 

These findings prompted us to reconsider the results of EPR spectra and to make more profound analysis of kinetic data for N2 reduction by catecholate vanadiu-m(II) complexes. The conclusion was that a tetra-vanadium structure for the complexes is in a better agreement with the EPR spectra than a trinuclear structure kinetic results also confirmed the tetranuclear structure of the complex [19], We therefore regard the tetranuclear structure as confirmed for unsubstituted and substituted catecholate complexes, at least for those so far investigated. 

The discrete trinuclear structure of [U3O(O-r-Bu) 0] consists of three distorted mutually confacial octahedra sharing an edge (Fig. 74) (487) with C I, crystallographic symmetry. 

Figure 34 Hemicapped trinuclear structure in [W3(/43-0)(02CCH3)6(H20)3][ZnBr4]-8H20.

The trinuclear structure of 40 was elucidated by X-ray crystallography. The molecule lies on a twofold axis through Zr(2), and the Zr-Zr and Zr-H distances are represented schematically in Figure 6. The three //-hydride ligands and three zirconium atoms are essentially coplanar, with //-hydrides above and below the plane. There are five hydrides and three zirconium atoms so compound 40 is formally mixed-valent Zr(m)Zr(lv)2. The shorter Zr-Zr distances in 40 compared to those seen in Zr(iv) dihydride dimers are consistent with the presence of Zr-Zr bonding.24... 

Gp sMs -HM -CDzCb 366. The crystal structure of the hafnium polyhydride complex reveals a fully asymmetric trinuclear structure with three widely differing Hf-Hf distances but the hydrides themselves could not be located. 

The high-yield synthesis of a luminescent trinuclear structure (28) in which deprotonated benzimidazole acts as the... 

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