Bridging coordination

Fig. 8.22) features a unique tris(bidentate) sex-tuply bridging carbonato ligand as well as three bidentate piT-carbonato ligands. Other chelating and bridging coordination modes are also known.< 2 >... 

Cp(CO)2Re(THF) forms the complex 105 upon reaction with thiophene (89JA8753, 910M2436). Similar species are known for 2- and 3-methyl-, 2,5-dimethyl, and tetramethylthiophene (91IC1417). Thiophene in 105 is S-coordi-nated, and the sulfur atom is pyramidal. Treatment of 105 with Fc2(CO)9 produces 106, where the thiophene ligand is bridge-coordinated via the sulfur atom to rhenium and four carbon atoms of the dienic system with iron (the coordination mode). The pyramidal nature of the sulfur atom is preserved. The -coordination of thiophene separates the dienic and sulfur counterparts of the ligand and decreases the TT-electron delocalization, which leads to the enhanced basicity of the sulfur atom. 

The general coordination modes of amidinate and guanidinate (R = NR 2) ligands are shown in Scheme 4. Both ligands display a rich coordination chemistry in which both chelating and bridging coordination modes can be achieved. By far the most common coordination mode is the chelating type A. 

Complex (868) is a unique example where urea forms a single-atom bridge between the proximate metal ions through its carbonyl-O atom.2080 An N,0-bridging coordination of (deprotonated) urea occurs in (869), 4 which forms in an equilibrium reaction between the active H302-bridged species... 

Trifluorophosphane can behave as a /x3 donor towards a triangular palladium core.559,360 The symmetrically bridging / -coordination mode has little precedent for tertiary ligands based on Group 15 atoms. The synthesis of a Pd1 dimer featuring a strongly bonded symmetrically bridging /i2-phosphole unit, which is the first example of this coordination mode for a tertiary phosphane, has been reported.561... 

Zinc dithiocarbamates have been used for many years as antioxidants/antiabrasives in motor oils and as vulcanization accelerators in rubber. The crystal structure of bis[A, A-di- -propyldithio-carbamato]zinc shows identical coordination of the two zinc atoms by five sulfur donors in a trigonal-bipyramidal environment with a zinc-zinc distance of 3.786 A.5 5 The electrochemistry of a range of dialkylthiocarbamate zinc complexes was studied at platinum and mercury electrodes. An exchange reaction was observed with mercury of the electrode.556 Different structural types have been identified by variation of the nitrogen donor in the pyridine and N,N,N, N -tetra-methylenediamine adducts of bis[7V,7V-di- .vo-propyldithiocarbamato]zinc. The pyridine shows a 1 1 complex and the TMEDA gives an unusual bridging coordination mode.557 The anionic complexes of zinc tris( V, V-dialkyldithiocarbamates) can be synthesized and have been spectroscopically characterized.558... 

A number of dialkyldithiophosphate zinc complexes were prepared and characterized in liquid and solid states, and as surface complexes on sphalerite. 31P NMR was used to characterize the coordination modes, whether terminal chelating or bridging between two metal centers. Correlations were made between data for the structurally characterized O.O -dicyclohexyldithiophos-phate zinc and the NMR of the surface complexes demonstrating bridging coordination between two neighboring zinc atoms on the synthetic sphalerite.568... 

Figure 16 Selected bridging coordination modes for polychalcogenide ligands (a) i-IkE 2kE (b) i-1kE1 2nEP (c) h3-1kE 2kE 3kEP (d) -IkE1 2kE3 3-k IP 4k IP.

Bridging coordination of a tertiary stibine ligand (type 2) occurs in binuclear complexes of rhodium (Equation 1).13,14... 

The N-2, N-4 bridging coordination mode has not (yet) been observed in Fe(II) spin crossover compounds, whereas the N-l, N-2 bridging mode has been confirmed by X-ray structure determinations of oligomeric and polymeric Fe(II) spin crossover materials. Depending on the nature of the substituted 1,2,4-triazole ligand and the presence of potentially coordinating an-... 

There are two principal modes of coordination of the carbon monoxide ligand in transition metal carbonyls terminal coordination, to a single metal atom, and bridging coordination, to two or more metal atoms. The Ols spectrum of Co4(CO)12, shown in Fig. 5, can be readily deconvoluted into two peaks corresponding to these two types of carbonyl groups109. This spectrum is useful for determining the relative chemical shifts for the two types because... 

Metal Complexes with Bridging Coordination to One Dinitrogen Molecule... 

Fig. 5 Schematic representation of different bridging coordination modes for phospho-lide rings...

Complexes with type II structures are compiled in Table II along with their S—S distances and S—S vibrational frequencies. There are several examples of complexes of structure type Ila (planar trans end-on bridging coordination). Vibrational spectroscopy 174) indicates that this structure occurs in [(CN)5Co(S2)Co(CN)5] (7). Trans arrangement of the metal atoms has been proved by X-ray structure determination for [(NH3)5Ru(S2)Ru(NH3)5]Cl4 2H20 15, 44). 

A series of bridged dinuclear [(bpy)2Ru(p-L)Ru(bpy)2] " and [(bpy)2Ru(/i-L)Os(bpy)2] complexes have been prepared in which the bridge coordination domains are phen ligands and the spacer is constructed by the stereoselective coupling of units through norbornene and epoxide functionalities. " " ... 

A number of cyano-bridged coordination polymers with Prussian Blue-related structures, in which extended linear Ag(CN)2 or AufCNH bridges take the place of the OT bridges of the prototype, show 3-fold interpenetration [1]. A typical example is that of Rb[Cd Ag(CN)2)3] consisting of Rb+ cations and a 3-fold interpenetrating polymeric anion, whose structure is shown in Figure 31. 

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