Orthometallation Reactions

There is a pronounced tendency for ruthenium cyclopentadienyl complexes with attached phosphorus ligands to undergo a wide variety of intramolecular metallation reactions. Heating (T75-C5H5)(PPh3)2RuMe in decalin for 24 hours leads to the orthometallated complex 135 in reasonable yield [Eq. (Ill)] (6,103). The mechanism presumably involves initial loss of 

Thermolysis of ruthenium vinyl complexes also promotes intramolecular orthometallation [Eq. (112)]. However, performing the reaction in the 

Addition of benzene or toluene in the presence of phosphine to the orthometallated species 135 yields ruthenium aryl complexes [Eq. (114)]. The reaction must involve initial dissociation of the nonorthometallated 

Orthometallation also occurs intermolecularly. Addition of azobenzene to (i75-C5H5)(PPh3)2RuMe affords the orthometallated species 139 in moderate yield [Eq. (115)] (104). The reaction between hexafluorobut-2-yne 

Cotton and G. Wilkinson, Advanced Inorganic Chemistry, 3rd Ed., p. 650. Wiley (Interscience), New York, 1972. 

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Neutral Ir complexes were obtained by an orthometalation reaction with ligands that contain a benzene ring attached to a functional group containing a donor atom such as 2-phenylpyridine (ppy) and benzo[h]-quinoline (bzq) [93]. The coordination of ppy and bzq ligands to metal is analogous to... 

Also unusual are orthometallation reactions involving 1-hydroxy-2,6-di-phenylbenzene, or its related lithium salt [Eqs. (58) and (59)] (229). Compound 69 is a stannoxane-bridged dimer in the solid state. In 70 the heterocycle is shown in schematic form, but it is identical to that in 69. 

The first indications came from reactions of C-H bonds in coordinated ligands with iridium centers. Prominent among this type of reaction are the ortho-metallation (see Orthometalation) reactions, especially of arylphosphine ligands in which a C-H bond ortho to the phosphorus adds to the iridium. Beyond this, however, there were also examples of C-H bonds of alkyl chains adding to low-valent iridium centers. These intramolecular C-H reactions seemed to be induced when the alkyl backbone of a chelating ligand place the C-H bond in very close proximity to the metal. 

Salts of mercury(II) and thallium(HI), such as mercury(II) acetate, Hg(OAc)2, and thallium trifluoroacetate, Tl(OCOCF3)3, are reactive electrophilic metallating species which attack benzene directly. Electron-donating groups in the aromatic ring accelerate the reaction in the conventional manner and direct attack to the ortho and para positions. In addition, metal-chelating substituents, such as amide, promote the reaction and direct attack to the 2-position in a manner similar to that seen in the directed orthometallation reaction. 

Another report (83) of an orthometallation reaction involves the reaction of 1,3-diacetylbenzene with [Mn(CH2Ph)(CO)s] to give the mono- and... 

Compared to manganese, little work has been carried out on analogous alkyl complexes of rhenium, although that which has may be divided into the same categories, namely, (1) reaction with transition metal hydrides, for example [CpW(H)(CO>3] (2) reaction with Lewis acids, for example, AlCUEt (3) orthometallation reactions (4) reaction with cationic species, for example, (5) reaction with anionic nucleophiles, for example, BF4" (6) reaction with neutral nucleophiles, for example, PPh3-... 

Triarylphosphites are capable of exhibiting multiple orthometallation reactions just as well as organophosphines, regardless of substituents on the aryl rings, as follows ... 

These results have been extended to other complexes of the 50 type it was ascertained that when substituted pyrazolate ligands were used, the orthometalation reaction becomes more selective (77). The X-ray crystal structure of [Rh2( -dmpz)2(/i-PC)Br(CO)(PCBr)J, 52, was also reported (77). 

In fact, this was the first example of an orthometallation reaction in organotin chemistry (157). 

This group was used as a bulky protective group to the intramolecular C-H insertion of a-diazo acetamides and in directed orthometalation reactions of aryl amides. The cumyl group is readily cleaved with CF3CO2H. Formic acid has also been used to remove a cumyl group. 

The orthometallation reaction with N donor atoms in the side chains usually forms five-membered chelated rings. There are exceptions, such as in the orthopalladation of N-arylamidines where six-membered rings are formed " ... 

Examples of orthometalation reactions [4] are presented in Scheme VIII. 1. 

Scheme VULl, Examples of orthometalation reactions. Relereiice numbers are in brackets.

Most reactions among cyclometalation reactions are orthometalation reactions. These reactions are used for the synthesis of orthometalation products or derivatives of orthometalation products. Pfefifer et al. [19] named these synthetic reactions chelation-assisted reactions in 2002. 

Recently, further orthometallation reactions of phosphines in dinuclear carboxylate complexes were carried out to give compounds of the type [Os2(/x-OOCR)2 /i-P(C6H4)Ph2 2Cl2]/ " The complex [Ru(/x-PhCONH)4Cl] reacts with PPh3 to cause breaking of the phosphorus-phenyl bond with the formation of the phenyl compound [Ru2Ph2(PhCONH)2 Ph2POC(Ph)N 2]. " ... 

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