Coordination chemistry bridging

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. 

AT-Heteroaryl ring systems are well-known as bridging functions between transition metal centers [12, 40, 41]. The pyridyl substituent is one of the representative examples of such systems that has been a widely used ligand in transition metal coordination chemistry [42]. However, the interest in group 13 metal chemistry of these ligands is of recent interest. Stalke et al. [43] have reported the synthesis and structure of the aluminum adduct Me3Al(/r-Py)PPy2 10. 

The finding of preparatively available iminoboranes RB = NR some years ago opened exciting new possibilities not only in B—N chemistry, but also in coordination chemistry. The first examples of iminoborane-transition-metal complexes have now been published. The structurally completely characterized t-BuB = NBu-t adds, like its alkyne analog, to the 03(00)5 fragment as a bridging ligand. When Co2(CO)g and t-BuB = NBu-t are dissolved in pentane at 0°C, warming to RT and evaporation of unreacted iminoborane yields (t-BuBNBu-t)Co2(CO)5 (86%) as a black solid, which can be recrystallized from ether-nitromethane (1 3) ... 

Chen, X.M. and Tong, M.L. (2007) Solvothermal in situ metal/ligand reactions a new bridge between coordination chemistry and organic synthetic chemistry. Accounts of Chemical Research, 40 (2), 162—170. 

In view of the versatility of A-heterocyclic carbenes as ligands and their structural diversity in silver(i) coordination chemistry, an extension of the work to ligands with two or more carbene moieties was reported. A dinuclear silver(i) complex 52 (Figure 21) with an o-phenylenedimethylene-bridged bis(carbene) ligand has been synthesized in 66% yield from silver(i) oxide and the bis(imidazolium) salt.88 The reaction to synthesize 52 has to be carried out in... 

Bipyridine (44-BP) is a bifunctional, non-chelating molecule, which consists of two planar pyridyl rings connected by a C-C bond in 4 and 4 positions. It has been extensively employed as a bridging ligand in coordination chemistry [291]. 

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