Bridged binuclear complex

There has been considerable interest shown recently in the synthesis, structure, and properties of binuclear complexes bridged by long chains of carbon of the type L M-(G=C) -ML . Such oligomers may exhibit novel properties such as one-dimensional conductivity, non-linear optical properties, or bulk spin alignment. Dinuclear... 

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. 

The binuclear complex [Mo2Cl2N2o] features a terminal nitrido ligand, N=, as well as terminal and bridging azido ligands, i.e. [ (MoCl(N)(t, -N,)2(/t,t -Nt)l2] Concatenations larger than N3 are rare. The planar bridging N4... 

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). 

It is of incidental interest that a little work has been done on dicobalt systems. Doyle and Sykes have made a study of the reduction of decammine-//-amidodi-cobalt(Ill), (NH3)5Co NH2-Co(NH3)5 , by V(II). Since the rate is independent of hydrogen-ion concentration the mechanism cannot involve an amide bridge and must be outer-sphere, as it is in the case of the reduction of Co(NH3)6 by V(1I) . Both the binuclear complex and Co(NH3)6 are inert to substitution but the former is capable of functioning as a two-equivalent oxidant. Thus the two likely mechanisms are... 

Strekas TC, Spiro TG. 1975. Resonance Raman spectra of superoxide-bridged binuclear complexes. p,-Superoxo-decacyanodicobaltate(5—) and /n-superoxo-decaamminedicobalt (5 +). Inorg Chem 14 1421. 

These conclusions are supported by another ESR study (Jd) made on some oxygenated cobaltoximes(II), which showed that the dioxygen species finally formed is best characterized as a peroxo-bridged complex these being reversibly formed binuclear complexes. 

The dark red Ir11 binuclear complex [Ir(CO)(P(/i-tolyl)3)(mnt)]2, formed via one-electron oxidation of [Ir(CO)(P(/ -tolyl)3(mnt)] by ferrocenium, contains chelating mnt ligands bridging the Ir—Ir bond.639 The X-ray crystal structure shows square-pyramidal geometry at each Ir, and an Ir—Ir bond length of 2.706(2) A. 

Balch, A. L. Binuclear, phosphine-bridged complexes progress and prospects. Pignoler, L. H. Ed. Homogenous Catal. Met. Phosphine Complex. 1983, 167, Plenum New York, 1983. 

Zinc complexes of cyclohexane-1,2-dione bis(thiosemicarbazone) have been formed in the neutral and doubly deprotonated form. The X-ray structures show distorted square-based pyramidal geometries for both complexes [ZnL(OH2)] and [Zn(H2L)Cl]Cl with the water or chloride occupying the axial position.886 The binuclear complex bis[l-phenylglyoxal bis(3-piperidylthiose-micarbazone)zinc] was synthesized by electrochemical methods and reveals a Zn2L2 with two tetradentate bis-thiosemicarbazone ligands bridging the metal centers.887... 

A similar type of oxygen complex has been observed during the oxidation of [Con(CN) s]-3 but it was not possible to show that this species was formed in the initial reaction step since with this system, as with the cobaloxime(II) system, the 1 1 adduct apparently reacts very rapidly with another molecule of pentacyanocobaltate(II) to form a diamagnetic binuclear complex with a bridging peroxide ligand 116). It appears that in the Bi2-system the bulk of the corrin ring does not allow formation of the diamagnetic binuclear complex. 

In this regard it would be interesting to consider the electronic structure of some binuclear complexes of other elements. For example, an analogous effect of the bridging ligands on the reverse energy order of <5M-M and <5g M MO s was... 

Subtle changes may influence the outcome of such reactions. Thus, the formation of a binuclear, halide bridged Fe-Cd complex was observed exclusively when starting from CdBr2 whereas only trinuclear Fe-Cd-Fe chains where found in the case of CdCl2 13c, d]. 

---