Coordinatively saturated complexes

Coordinatively unsaturated complexes and those giving easily such species by ligand dissociation favor pathways related to that described in Eqs. (10) and (13). Coordinatively saturated complexes reduce halocarbons via outer-sphere ET [193, 194]. In cases of electrochemical dehalogenations, the species formed by one-electron reduction of the mediators on the cathode often react in this way [156, 157, 198], For example (Eq. (14)) [157, 166] ... 

P(OPh)3 leads to the coordinatively saturated complex K2 [15], As complex K2 is coordinatively saturated, P(OPh)3 must dissociate in order to obtain a catalytically active 16-VE d -Ir complex. Similar C—H activation was later found for (phosphoramidite)Ir complexes. 

Class B Type MA, . Neutral coordinatively saturated complexes formed between the metal ion and a lipophihc organic acid. This class contains the large group of metal-organic chelate compounds. For monbasic acids forming bifunctional chelates, z = N/2. They belong to the extraction Type in-B, treated in section 4.8. 

In the addition mechanism, the coordination number of uranium is increased from six to seven, whereas in the substitution mechanism, there is no increase in the coordination number. The absence of any synergistic effect for uranium(IV) and thorium(IV),127 which give coordination-saturated complexes M(HA2)4 with organophosphoric acids in which the metal ions are eight coordinate, is in accord with the addition mechanism. 

This interpretation is consistent with the increased yield of aldehyde which requires that Eq. (34) should be able to compete effectively with Eq. (33) for cobalt hydrocarbonyl. It is also consistent with the decreased branching found since such isomerizations are reduced by coordinatively saturated complexes. 

Similarly, Pd(0) and Pt(0) form complexes using their d10 electrons. The numbers of d electrons of major transition metals used for the complex formation are shown in Table 2.1. Coordinatively saturated complexes are formed by the donation of electrons from the ligands until total numbers of the electrons reach 18. 

Also, alkyls can bridge two metal centers, for example like methyl groups in (CFT3)2Al(pL-CFT3 2A 1(C E 1 )2 [184e], Coordinately saturated complexes are more... 

Davidson and Vasapollo374 375 have described the reactions of [ W(/ -Br)Br(CO)4 2] with three dienes (diene = cod, nbd and cot) to yield the coordinately unsaturated diene complexes [WBr2(CO)2(r/4-diene)]. These react with one equivalent of L L = CNBu , PMe2Ph, P(OMe)3 to afford [WBr2(CO)L(p4-diene)] via the coordinatively saturated complexes... 

The stereochemistry of the neutral ligand also affects the properties ofthe catalyst. Although [RhCl P(2-C6H40Me)3 3] initially reduces alkenes rapidly, the reaction ceases before all the aUcene has been consumed because of the formation of the coordinatively saturated complex (3). 

Another condition which is essential in enhancing the reactivity of 77-allyl compounds towards substitution is the easiness of the 7r,<7-rearrange-ment for the allyl ligand (135, 140-146). When the TT-allyl ligand is converted entirely to its u-bonded state there occurs a consequential increase of the metal s coordinative unsaturation. Hence dimethyl sulfoxide readily substitutes all the ligands in the electronically and coordinatively saturated complex (7r-C3H5)Fe(CO)jI (147). 

Reaction 10.4 is one of the prototypical reactions shown in Scheme 10.1 (ligand substitution) and this occurs much more rapidly in radical species. The much greater rate of ligand substitution for radical complexes compared to coordinatively saturated complexes can lead to radical chain substitution reactions. One of the earliest reports is that of Byers and Brown in 1975,11 as shown in the reaction sequence below ... 

Since [Np4] is a coordinatively saturated complex fluoro cation, the syntheses of its salts are generally difficult. A limited number of salts can be prepared directly from NFj, and these salts can then be converted by indirect methods into other [NFJ salts that are important for solid propellant NFj-Fj gas generators or reagents for the electrophilic fiuorination of aromatic compounds. 

---