Complexes with Bridging Groups

Numerous dinucleating macrocyclic and macrobicyclic ligands have been synthesized, in particular by the versatile amine + carbonyl — imine reaction they form dinuclear metal complexes as well as cascade complexes with bridging groups [2.58-2.63, 3.24-3.27, 4.1-4.4], for instance in dicobalt complexes that are oxygen carriers [3.26]. 

Dimeric complexes with bridging group VB ligands are prepared by the following... 

The first method for preparing alkylidene-bridged bimetallic complexes with bridging groups other than methylene e.g. (36) has been discovered, and preliminary experiments have shown that these too are capable of converting ketones into olefins, e.g. cyclohexanone -> (37), and esters into vinyl ethers. ... 

Distibines react as monodentate (type 5) or bridging bidentate (type 6) ligands through donation of the lone pairs of electrons to main group or transition metal centers. Fission of the Sb-Sb bond leads to complexes with bridging R2Sb ligands (type 7, 8 and 9) (Scheme 3). 

Table 33 Dinuclear Copper(II) Complexes with Bridging Organic Groups...

Attempts have been made to mimic proposed steps in catalysis at a platinum metal surface using well-characterized binuclear platinum complexes. A series of such complexes, stabilized by bridging bis(diphenyl-phosphino)methane ligands, has been prepared and structurally characterized. Included are diplati-num(I) complexes with Pt-Pt bonds, complexes with bridging hydride, carbonyl or methylene groups, and binuclear methylplatinum complexes. Reactions of these complexes have been studied and new binuclear oxidative addition and reductive elimination reactions, and a new catalyst for the water gas shift reaction have been discovered. 

Ruff (71a) was also able to obtain halogen-bridged anionic complexes with different Group VIB metals, namely, [CrW(CO)i0Br] and [CrMo(CO)10I]. A little later, we used the same method to gain access to dinuclear NCS-bridged anions with heterometals and bent M—NCS —M bonds (72) ... 

The deviation from the linearity at the gold atom (C-Au-As angle of 166.8(4)°) is only moderate if compared with other complexes with bridging mesityl groups, e.g., [Au5(mes)5].83 It is noteworthy that the mesityl bridge is not symmetrically disposed, in contrast with the usual symmetrical disposition of the aryl ligand in the examples mentioned above. 

R H, R" = CH CH2 R = H, R = C02Et) to give bridging alkylidene complexes (51). The latter undergo dynamic behaviour in solution. Herrmann et al(31) have prepared a number of related dirhodium complexes with bridging alkylidene groups by reacting either... 

Methyl sulfonic acid reacts with antimony(V) chloride and water to yield Cl3Sb0(0H)(02S(0)CH3)SbCl3, a binuclear complex with bridging sulfonato groups. Binuclear Sb(V) complexes are also formed from SbCls and diphenylphospho-ric acid or benzylphosphonic acid alkyl ester in water. ... 

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