Bridging Bidentate Ligands

A wide variety of complexes in which a bidentate ligand bridges two gold centers have been described. The dinuclear units may exhibit intramolecular, intermolecular or 

The luminescent properties of complexes [Au2C12(P P)] [P P = bis(2-diphenyl-phosphino)phenylether (dpephos), 9,9-dimethyl-4,5-bis(diphenylphosphino)xan-thene (xantphos), and 4,6-bis(diphenylphosphino)dibenzofuran (dbfphos)] have been studied. Aurophilic intramolecular interactions are present in [Au2Cl2(dephos)] and [Au2Cl2(xantphos)] which are probably responsible for the presence of a low energy band [209]. 

In many cases the molecules associate though intermolecular aurophilic interactions leading to the formation of chains, some examples are [Au2 S2CNPr2 2], 

2D structure. The gold-gold distance increases from 2.711(3) A in the starting product, to 2.9047(17) A in the final chain [292]. 

Homoleptic complexes with bidentate C C donor ylide derivatives are well known. Oxidative addition of some gold(I) [Au2 (CH2)2PR2 2] species by addition of halogen, pseudo-halogen, or alkyl halide affords dinuclear Au(II) complexes which 

---

The bridging PBu 2I I molecule is not as tightly bonded as other bridging bidentate ligands. This can easily be confirmed by comparing the reactivities of monodentate phosphines.832 The strength of the overall Pd2(/ -PBu 2[ I) interaction is greater than that of a terminal Pd—Bu 2H bond.832... 

The nature of the bridging ligand is also important the quadrimle bonds (the ranges are given) shorten with type of bridging bidentate ligand in the order 18 ... 

The tris(2-cyanoethyl)phosphine can act either as a monodentate phosphorus donor ligand or as a bidentate mixed donor ligand. The red square planar [NiX2L<2] complexes (X = Cl, Br) transform in the solid state into blue six-coordinate isomers which have a polymeric structure involving bridging bidentate ligands (Scheme (2).1178,1184,1192... 

The metal complexes of QDO and PDO have been the subject of some studies since the middle of the 20th century [67]. In these cases, the hetero cycle N-oxidc has acted either as a unidentate N-oxidc oxygen ligand or as a chelating or bridging bidentate ligand when heterocycle substituents were involved in the coordination processes. A wide variety of metals have been used in the coordination reactions, among Cr(III), Mn(ll), Fe(III), Co(II), Ni(Il), Cu(II), and Zn(ll). 

There are also a few dimeric complexes containing a bridging bidentate ligand. Particularly noteworthy are the binuclear dinitrogen complexes [ RhH(PR3)2 2N2] (R = Pr1,55 Cy55,56). 

In these compounds, sulfonate ligands act as bridging bidentate ligands, similar to a carboxylate ligand,... 

The axial coordination sites of M2(p,-L2)4-type complexes (where L2 is a bridging bidentate ligand) are generally available for bonding to ligands, and polymers will result if bidentate ligands are bonded at these sites ... 

The structures and vibrational spectra of a large number of nitrato complexes have been reviewed by Addi n et and Rosenthal. X-ray analyses show that the NO3 ion coordinates to a metal as a unidentate, symmetric and asymmetric chelating bidentate, and bridging bidentate ligand of various... 

---