Single-bridge complexes

Apart from interactions between dissimilar molecules, singlebridge complexes are formed only in special cases in which steric effects prevent full polymeric association. A common case of such steric effects is that of or / o-substituted phenols, which have been 

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H2P04, and CH3COOH in acidic solution give complexes of type X. As shown in Eq. (64), the conversions are reversible and involve intermediate formation of the corresponding singly bridged complexes IX (376-386). 

The chloro- and bromo-bridged complexes were first prepared by Werner (7). Werner originally formulated these complexes as singly bridged complexes (structure IX), but the /i-amido-/<-chloro and fi-amido-/i-bromo structures have recently been demonstrated by crystallographic studies (387, 388). The equilibrium constant Kl2 = Kt x K2 has been determined spectrophotometrically and the formation of structure X for X"- = Br is less favorable than its formation for the chloro analog (376, 379) (Table XXXVI). The equilibrium between... 

Pyridyldiphenylphosphine forms a number of homo-and heteronuclear palladium dinuclear clusters with short Pd-M bonds (about 260 pm). They are usually made by comproportionation of a Pd(II) complex and a second complex in a low oxidation state, for example, Pd(0), Rh(I), Ru(0). For these derivatives, head-to-head and head-to-tail isomers are possible, but the latter seems to be preferred (Figure 2). The metal-metal bonds in these derivatives are not as reactive as in the corresponding dppm complexes and insertion reactions do not occur. Some single-bridged complexes, such as [Cp(CNR)Rh(/u.-PPh2Py)Pd(CNR)Cl]+ (Pd-Rh distance 263.1 pm) are also known. 

The singly bridged complex [Mn2(/n-SEt)(CO)4(7j-CsH4Me)2] (77) shows two reversible, one-electron reduction waves ( = 0.17 and... 

Singly bridged complexes are less numerous than doubly bridged ones. Representative examples are the homoleptic species [M(pz )] [M = Cu(I), Ag(I), and Au(I)]. Notably, the number of these binary complexes increased in the last years as well as their X-ray crystal structures (13). 

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