Mixed-ligand complexes substitution

Heterocyclic nitrogen donors and their adducts with zinc chloride have been studied.623,624 A large number of other ligand systems have also been characterized, for example, zinc halide adducts of 2,2-dimethylpropane-1,3-diamine and hexamethylphosphoramide have been studied.625,626 The formation of mixed ligand complexes with chloride and substituted pyridines has been studied.627 The zinc tris(pyridyl) chloride anion has also been structurally characterized.628 Manganese(II) ions have been used to probe the stereochemistry in reactions of zinc halides with pyrazine.629... 

It has long been known that, when bound to cobalt(II), the pyridine-based chelate ligands 2,2 -bipyridine (bipy), 1,10-phenanthroline (phen), and 2,2 6, 2"-terpyridine (terpy) form complexes that react with dioxygen in aqueous solution (32-34). The mixed-ligand complexes [Co(terpy)(bipy)]2+ and [Co(terpy)(phen)]2+ can act as oxygen carriers in aqueous solutions at pH values as low as 3.0 (34b), and the superoxo species thus formed are apparently dinuclear. In addition, the dinuclear bipyridine complex [(bipy)2Coin(/ 2-0 )(/ 2-02 )CoIn(bipy)2 ]3+ has been shown to catalyze the oxidation of 2,6-di-ter -butylphenol to the feri-butyl-substituted diphenoquinone and quinone (35). 

Subnormal V02+ complexes (93) of SBs derived from 2-hydroxynaphthaldehyde and o-aminophenol and some substituted derivatives have also been obtained.765 The ESR spectra of the complexes (93 R = R = R" = H R = Cl, R = R" = H) in polycrystalline solids at room temperature exhibit two parallel lines, two perpendicular lines and a broad line around 1600 G due to the AM% = 2 transition. At 77 K, both high- and low-field spectra exhibit hyperfine splittings. Several complexes of type (93) were also studied by Carlisle et al. (Table 41, 27-34).766,767 v(V=0) values of complexes (93) lie in the range 955-1000 cm-1 and the compounds exhibit only one d-d band in the region 620-700 nm. As in the case of (91 R = R = H), on treatment of compound (93 R = R = R" = H) with phen the dimer is broken and a mixed-ligand complex is obtained.765... 

The mixed-ligand complexes RNiX3B (B = PPh3, py and substituted pyridines) have been prepared in general by the reaction of RX and NiX2 in the presence of the Lewis base B in hot butanol.2223 "33,2234,2238,2239 2244 These complexes have a distorted tetrahedral structure2238,2239 and their spectral and electronic properties have been investigated in detail.2245... 

The products of partial substitution for the OR-groups, i.e., alkoxocarbox-ylates, P-diketonates M(OR)mX , where X= RCOO, acac, thd, etc.—the mixed-ligand complexes—usually are more soluble and stable than M(OR) , as their molecules contain the chelate cycles. Mehrotra et al. [223] have described a great number of such products (usually liquid or amorphous), in which individuality appeared sometimes questionable. During recent years, however, in connection with the application of these compounds to the synthesis of oxides, interest in them has increased, and a number of them have been isolated and structurally characterized (Chapter 7). Unfortunately, length restriction did not permit us to present a complete review of their chemistry in this book. 

A number of molecular mechanics studies of metal-cyclopentadienyl complexes have been reported recently. The systems studied include linear metallocenes (in particular ferrocene), ferrocene derivatives (such as complexes with substituted cy-clopentadienyl ligands, bis(fulvalene)diiron complexes, ferrocenophanes and mixed-ligand complexes with carbonyls and phosphines), and nonlinear cyclopentadienyl complexes 8,153,221 231]. 

Mixed-ligand complexes such as nickel dithiolene diimine can be prepared via ligand substitution reactions (Eq. 6) (52). 

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