Trinuclear

Deviation includes, in fact, the summation of steric and electronic effects, and basicity is somewhat a useful predictor for properties of complex dyes (solvent sensitivity, isomeric forms of trinuclear dyes) and gives also semiquantitative data for color structure relation (atomic)... 

Polymethines with branched polymethine chains also exist. Among these, PMD with symmetrically branched chains are the best known they are referred to as trinuclear polymethine dyes (TPMD) (6). 

Higher methinylogous trinuclear symmetrical [2.2.2]heptamethinecyariines (38) are synthesized by the interaction of appropriate residue-forrning synthons, which contain an active center with triformylmethane as a branched chain-forming synthon (33,36) ... 

Reaction of Fisher s base and its quaternary salt with the trisacetal leads to the only synthesized [3.3.3] decamethine dye (33). Higher methinylogous trinuclear dyes have not been obtained. 

Tungsten pentachlofide [13470-13-8], WCl, mp 243°C, bp 275.6°C, is a black, crystalline, deHquescent soHd. It is only slightly soluble in carbon disulfide and decomposes in water to the blue oxide, 200 2. Magnetic properties suggest that tungsten pentachlofide may contain trinuclear clusters in the soHd state, but this stmcture has not been defined. Tungsten pentachlofide may be prepared by the reduction of the hexachloride with red phosphoms (9). 

The reaction between a trinuclear metal carbonyl cluster and trimetbyl amine borane has been investigated (41) and here the cluster anion functions as a Lewis base toward the boron atom, forming a B—O covalent bond (see Carbonyls). Molecular orbital calculations, supported by stmctural characterization, show that coordination of the amine borane causes small changes in the trinuclear framework. 

For trinuclear cluster complexes, open (chain) or closed (cycHc) stmctures are possible. Which cluster depends for the most part on the number of valence electrons, 50 in the former and 48 in the latter. The 48-valence electron complex Os2(CO)22 is observed in the cycHc stmcture (7). The molecule possesses a triangular arrangement of osmium atoms with four terminal CO ligands coordinated in a i j -octahedral array about each osmium atom. The molecule Ru (00) 2 is also cycHc and is isomorphous with the osmium analogue. 

Reaction with vatious nucleophilic reagents provides several types of dyes. Those with simple chromophores include the hernicyanine iodide [16384-23-9] (20) in which one of the terminal nitrogens is nonheterocyclic enamine triearbocyanine iodide [16384-24-0] (21) useful as a laser dye and the merocyanine [32634-47-2] (22). More complex polynuclear dyes from reagents with more than one reactive site include the trinuclear BAB (Basic-Acidic-Basic) dye [66037-42-1] (23) containing basic-acidic-basic heterocycles. Indolizinium quaternary salts (24), derived from reaction of diphenylcyclopropenone [886-38-4] and 4-picoline [108-89-4] provide trimethine dyes such as (25), which absorb near 950 nm in the infrared (23). 

Se3Bri3- < > SeCls , TeClj-, TeCle ", etc.< > The anion structures are much as expected with the Se species featuring square planar (pseudo-octahedral) units, and the trinuclear Se " anions as in the tellurium analogue above. See also p. 776. There are, in addition, a fascinating series of bromoselenate(II) dianions based on fused planar SeBr4 units, e.g. Se3Brg ", Se4Bri4 ,... 

A few trinuclear oxo-centred carboxylates [V30(RC00)gL3]+ of a type more common for later transition metals (see Fig. 23.9, p. 1030) have been obtained, as well as [Nb302(MeC00)6(thf)3]+ whose structure differs essentially only in that there are two bridging O atoms above and below the Nb3 plane. 

Other mononuclear complexes include the tetrahedral [Mo(NMe2)r] and the octahedral Li2[Mo(N Me2)6].2thfi hut recent interest in the chemistry of the M" ion has eentred on the trinuclear 0x0 and thio complexes of Mo and W, particularly the former. They are of three main types. The first may be conceptually based on the [M3O11I unit found in the aquo ions [.M304(H209] (M = Mo. W). It contains a... 

Figure 23.8 Trinuclear. M-.M bonded species of Mo" and W. (a) (b) and (c) are alternative representations of the -MjOij unit (a) emphasizes its relationship to the edge-sharing octahedra of the Mj group in polymetallate ions (b) shows the (rrj-O) (rrr-Olj bridges and M-M bonds of its MiOs incomplete cubane" core and (c) emphasizes its triangular centre by viewing from the unoccupied comer of the cuboid (d) and (e) offer the same perspective as (c) but of (Mj02(02CR)6(H20)3] and (Mjirrj-X)(rti-OR)(OR)9] stmetures respectively.

The second type of trinuclear compounds containing (M302(02CR)(,(H20)3] and obtained by the reaction of M(CO)6 (M = Mo, W) with carboxylic acids, features a similar triangle of M-M bonded metal atoms but this time capped on both sides by hj-O atoms (Fig, 23.8d). Complexes m which either one or both of these capping atoms arc replaced by /iy-CR, alkylidene. 

Trinuclear basic acetates [Ru30(02CMe)gL3]+ have also been prepared apparently with the same constitution as the analogous Fe and Cr compounds (p. 1030). 

The structures are shown in Fig. 26.8c and d and differ in that, whereas the Ir compound consists of a tetrahedron of metal atoms held together solely by M-M bonds, the Rh and Co compounds each incorporate 3 bridging carbonyls. A similar difference was noted in the case of the trinuclear carbonyls of Fe, Ru and Os (p. 1104) and can be explained in a similar way. The M4 tetrahedra of Co and Rh are small enough to be accommodated in an icosahedral array of CO ligands whereas the larger Ir4 tetrahedron forces the adoption of the less dense cube octahedral array of ligands. 

Isolation and characterization of stereoisomers in di- and trinuclear complexes with N-heterocyclic ligands 98CSR185. 

Imidazole with [(r -C3Hj)2Rh(acac)] gives the trinuclear complex 60 (86JCS(D)2193). 

L = C3H3, C H ) and then [Rh(acac)(CO),] to yield the tetranuclear species 180 (85ICA(i00)L5), where the heterocyclic ligands are tridentate. The product reacts with the rhodium(I) dimer [Rh(CO)2Cl]3 to give the trinuclear complex 181. In the solid state, the molecules of this complex form the intermolecular stacks along the z-axis. 

Tetrazole with [(T) -C3Hj)2Rh(acac)] gives the trinuclear complex 191 (86JCS(D)2193). This product with [Rh( j.-Cl)(CO)2]2 produces the mixed-valence trinuclear species 192. 

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