Ruthenium-benzyne complex

A ruthenium-benzyne complex activates C-H bonds through a sequence of reductive elimination and oxidative addition reactions . ... 

The ruthenium benzyne complex previously discussed is an excellent entryway into. activation of oxygen- and sulfur-hydrogen bonds. Reactions proceed cleanly under mild conditions ... 

The ruthenium benzyne complex also reacts with nitrogen and oxygen donors ... 

A ruthenium benzyne complex is derived by the elimination of methane or benzene... 

Azaruthenacyclopentane (31) and oxaruthenacyclopentane (32) were prepared by insertion into a ruthenium benzyne complex (Scheme 4) <91JA3404>. 

The reactions of benzyne complexes of zirconium " also occur by electrophilic attack at an M-C bond. The isolated phosphine adduct of a zironocraie-benzyne complex reacts with ketones to imdergo insertion into one of the M-C bonds and with alcohol to make an aryl alkoxo complex, as shown in Equation 12.67. An electron-rich ruthenium-benzyne complex also reacts with electrophiles, such as borzaldehyde or carbon dioxide, to form products from insertion, as shown at the top of Equation 12.68. It also reacts with weak acids, such as aniline, to form products from formal protonation at the Ru-C bond, as shown at the bottom of Equation 12.68. - This reaction with aniline could occur by initial protonation at the metal, followed by C-H bond-forming reductive elimination, or by direct protonation of the M-C bond. Initial protonation of the metal center was proposed. 

Figure 16.7 Structure of ruthenium benzyne complex (( / -C<>H4)Ru(PMe3)4) [28].

Benzyne complexes shown in Scheme 16.5 form a similar octahedral structure as shown in Figure 16.7. The bond length of C=C of benzyne is 1.3555 A, it is shorter than the other C=C bonds (1.372 A—1.411 A). The benzyne complex is a white solid, very liable to air, but it is stable for several months at room temperature under an inert gas atmosphere. It reacts with water at 20 °C and the 7r-coordination changes to two c-bonds of phenyl and OH bond [28]. Ruthenium phosphine reacts with f-butylacetylene to afford a ruthenium carbene (Br2(PPh3)2Rn=C=CH(t-Bu)) via an acetylene-7r-complex as shown in Figure 16.7. 

A tetrakis(trimethylphosphine)ruthenium complex of benzyne has been prepared6 26 by a reaction similar to that used for the Group 4 and 5 metals thermally induced /3-hydride elimination of methane or benzene from 1 or 2, respectively [Eq. (3)]. A careful study of the kinetics of the elimination of methane from 1 revealed that dissociation of trimethylphosphine pre-... 

It is useful to explore this analogy between known alkyne systems and potential benzyne ones. For example, alkynes react with ruthenium carbonyl to form the Ru4( --alkyne)(CO)i2, which form an octahedral RU4C1 arrangement with the metal atoms in a butterfly geometry. Since the synthesis cannot be adapted to arynes, another method is needed. Oxidative addition of aryl iodides to Ru3(CO)i2 gives the aryl complexes described in Sec. 1.14.4.5. Flowever, we have... 

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