Ligand exchange/substitution

Up to now, no stable adducts of type A where one of the bridging atoms X is replaced by a chemically different base or the tin atom by another Lewis acid have been synthesized. Nevertheless, this type of adduct is believed to play an important part in ligand exchange or substitution reactions. 

The synthesis of asymmetrically substituted stannylenes is most efficiently achieved by ligand exchange reactions between two stannylenes, SnXj and SnY2 (see Chapter 4). For example, the stannylenes [(Me3Si)2NJClSn and (C5H5)ClSn can be synthesized according to Eqs. (36) and (37) 86,93 94). 

The study of rapid, intermolecular ligand exchange between square-planar complexes trans-Ir(CO)L2X (X = C1 or Me, L - PPh3, P(p-tolyl)3, or PMePh2) by variable-temperature 31P NMR spectroscopy indicates that the reaction proceeds through dissociation of phosphine from the metal center and a subsequent associative substitution with other complexes 559,560 Ligand exchange between square-planar Ir and Pt complexes is slow. 

All these complexes readily undergo ligand exchange reactions [65], including substitution of [TcNCl2(PPh3)2] by more basic phosphines [3]. Tri(cyanoethyl) phosphine (L) yields the anionic NBu4TcNX3L] (X = Cl, Br) on reaction with... 

L)AuC=CR complexes can also be obtained by ligand exchange starting from precursors with homoleptic substitution (PPN+= (Ph3P)2N+ Equation (19)).71... 

E. The Chemical Mechanism at the PR3 Stage V. Digression to Ligand Exchange and Substitution... 

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