Binuclear structure

A new route to Nb8(/i3-0)2( 2-0)8(M2-0Et)6(0Et)i4 based upon condensation of NbO(OEt)3 is available and its structure has been confirmed.273 274 The tantalum analog has an equivalent structure.275 Three other oxo-alkoxo clusters of Ta have been characterized structurally binuclear Ta2(/i2-0)(M2-0Pi,1)(0Pr1)7(Pr10H) pentanuclear Ta5( 3-O)4(/i-O)3(/i2-OBut)(OBut)i0, and hepta-nuclear Ta7(//3-0)3(//2-0)6()u2-0Pr1)4(0Pr1)i3.275 276... 

Marmorstein, R., Harrison, S.C. Crystal structure of a PPRl-DNA complex DNA recognition by proteins containing a Zn2Cys6 binuclear cluster. Genes Dev. 

This binuclear complex is also fluxional and has the structure shown in Fig. 7.4a. A1(BH4)3 reacts readily with NMe3 to give a 1 1 adduct in which Al adopts the unusual pentagonal... 

Numerous tetrahedral halogeno complexes [T1" X4] (X = Cl, Br, I) have been prepared by reaction of quaternary ammonium or arsonium halides on TIX3 in nonaqueous solution, and octahedral complexes TI "X< ] (X = Cl, Br) are also well established. The binuclear complex Cs3[Tl2"Cl<)J is an important structural type which features two TlCls octahedra sharing a common face of 3 bridging Cl atoms (Fig. 7.9) the same binuclear complex structure is retained when Tl " is replaced by Ti ", V ", Cr " and Fe " and also in K3W2CIS and CssBiily, etc. 

Figure 13.11 Structure of the binuclear anion [Sbj OCle] " showing the bridging oxygen and chlorine atoms and the pseudooctahedral coordination about Sb the O atom is at the common apex of the face-shared square pyramids and the lone-pairs are trans- to this below the SbCU bases. The bridging distances Sb-Cl are substantially longer than the terminal distances Sb-Cl,.

Figure 13.19 Proposed structures for (a) the tridentate cycZo-polyarsane complex [Cr(CO)3(As5Mes)], and (b) the bismonodentate binuclear complex [ Cr(CO)sl2(As5Me5)].

Binuclear aromatic hydrocarbons are found in heavier fractions than naphtha. Trinuclear and polynuclear aromatic hydrocarbons, in combination with heterocyclic compounds, are major constituents of heavy crudes and crude residues. Asphaltenes are a complex mixture of aromatic and heterocyclic compounds. The nature and structure of some of these compounds have been investigated. The following are representative examples of some aromatic compounds found in crude oils ... 

They have binuclear tetracarboxylate-bridged lantern structures in the butyrate Os-Os is 2.301 A and Os-Cl 2.417 A. Most reactions involve cleavage of the Os-Os bond (Figure 1.66). 

Theory of bridge bonding and the structure of binuclear coordination compounds. B. Jezowska-Trzebiatowska and W. Wojciechowski, Transition Met. Chem. (N.Y.), 1970,6,1-58 (203). 

A crystal-structure determination on [Ni(PhCH2CS2)2] showed evidence of a Ni-Ni bond (Ni—Ni distance, 256 pm) in a bridging, acetate-cage, binuclear complex (363). Each nickel atom is 5-coordinate and is in a tetragonally distorted, square-pyramid spectroscopic evidence for a Ni-Ni bond has been obtained (364). The polarized crystal spectra showed more bands than predicted for a mononuclear, diamagnetic, square-planar nickel(Il), and the spectra are indicative of substantial overlap of the d-orbitals between the two nickel atoms. The bis(dithiobenzation)nickeKII) complex was found to exhibit unusual spectrochemical behavior (365). 

In nickel and palladium dithiobenzoato complexes, four-membered chelate rings are formed (366), whereas, in the corresponding phenyl-dithio acetates [M2(S2CCH2Ph)4], the dithio ligands act as bridging groups between the two metal atoms, with the formation of binuclear units (367). The molecular structure of the latter compounds shows that each metal atom is coordinated to four sulfur atoms and to the other metal atoms in a square-pyramidal geometry. Other evidence for... 

It will be noted that conversion of the intermediate V(OH) Cr " to products involves a different number of H ions than its conversion back to reactants. It is considered likely that the binuclear intermediate has an inner-sphere structure. On applying the steady-state approximation to the concentration of this intermediate, it follows that... 

Gold palladium binuclear complexes [141] can be synthesized by reaction of [Au (C6F5)(tht)] with the palladium derivative trans-[pdRR (dppm)2] where R = R = QF5 R = R = CgCls R = C Fs, R = Cl. It was however not possible to distinguish the two structures for these complexes shown in Figure 3.20 ... 

Mono- and binuclear gold(I) and gold(III) complexes with S2C-PR3 ligands. X-ray crystal structures of tris (pentafluorophenyl)... 

Further examples of emissive cyclometallated gold(III) complexes are [Au(L)Cl] (L = tridentate carbanion of 4 -(4-methoxyphenyl)-6 -phenyl-2,2 -bipyridine) [53], as well as mono- and binuclear bis-cyclometallated gold(III) complexes, namely [Au (C N C )L ]" (C N C = tridentate dicarbanion of 2,6-diphenylpyridine L = depro-tonated 2-mercaptopyridine (2-pyS ), n = 0 L = PPh3 or 1-methylimidazole, n = 1) and [Au2(C N C )2(P P)](C104)2 (P P = dppm, dppe) respectively [54]. The crystal structures of the binuclear derivatives show intramolecular interplanar separations of 3.4 A between the [Au(C N C)] moieties, implying the presence of weak n-n interactions. The mononuclear complexes show absorption with vibronic structure at 380-405 nm (e > 10 cm ), attributed to metal-perturbed intraligand transition. 

Luminescent gold(l) acetylide complexes. Photophysical and photoredox properties and crystal structure of [ Au(C = CPh) 2 (p-Ph2PCH2CH2PPh2)]. Journal of the Chemical Society, Dalton Transactions, 2929-2932 (d) Che, C.-M., Wong, W.-T., Lai, T.-F. and Kwong, H.-L. (1989) Novel luminescent binuclear gold(I) isocyanide complexes. Synthesis, spectroscopy, and X-ray crystal structure of Au2(dmh)(CN)2 (dmb = 1,8-di-isocyano-p-menfhane). Journal of the Chemical Society, Chemical Communications, 243-244. 

Chan, M.C.-W. and Che, C.-M. (1998) Application of 2,6-diphenylpyridine as a tridentate [C N C] dianionic ligand in organogold(III) chemistry. Structural and spectroscopic properties of mono- and binuclear transmetalated gold(III) complexes. Organometallics, 17, 3505-3511. 

A special representative of class IIIA is the Creutz-Taube complex [101]. This is a binuclear complex [(NHjlsRufpyrazinelRufNHj) ]. Various experimental results led to conflicting conclusions concerning its electronic structure. A combined attack [101] has shown, however, that we are not dealing with a... 

In contrast with the Schiff base salen, salicylaldehyde oxime (79) (salox) complexes of Co have received comparatively little attention, but a series of bis-bidentate divalent complexes of the form iraiis-Co(sa 1 ox)2( D M SO)2 have been reported.343 The heterocyclic bidentate oxime violurate (lH,3H-pyrimidine-2,4,5,6-tetrone 5-oximate, Hvi) (80) and its /V-methyl (mvi) and /V,/V -dimethyl (dmvi) derivatives form high-spin divalent [Co(vi)]+ and Co(vi)2 complexes, whereas [Co(vi)3] is low spin.344 The mixed-ligand Co(dmvi)2(phen) complex is also low spin. The crystal structure of m-Co(pxo)2Br2 (pxo = 2-acetylpyridine-l-oxide oxime) is isostructural with the Ni11 relative.345 The dichloro complex also adopts a cis configuration. The tridentate dioximes 2,6-diformyl-4-methylphenol dioxime and 2,6-diacetyl-4-methylphenol dioxime (Hdampo) form binuclear complexes of the type (81a) and (81b) respectively.346 Cobalt oxide nanoparticles were prepared by... 

The binuclear species (69) and (70) are prepared from the reaction of [Ir(PEt3)2(C2H4)2Cl] with liquid NH3, followed by treatment with NaBPh4 or pyridine, respectively. Both structures are determined by X-ray crystallography and show Ir—Ir distances of 3.33 A and 3.34 A, respectively.94... 

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