Arene complexes preparation

Ku9ukbay, H., Cebnkaya, B., Guesmi, S., Dixneuf, P.H., New (carbene)ruthenium-arene complexes preparation and uses in catalytic synthesis of furans, Organometallics 1996, 15 2434-2439. 

As was suggested in the preceding discussion, most of the arene complexes isolated by metal-atom techniques are benzene derivatives. However, heterocyclic ligands are also known to act as 5- or 6-electron donors in transition-metal 7r-complexes (79), and it has proved possible to isolate heterocyclic complexes via the metal-atom route. Bis(2,6-di-methylpyridine)Cr(O) was prepared by cocondensation of Cr atoms with the ligand at 77 K (79). The red-brown product was isolated in only 2% yield the stoichiometry was confirmed by mass spectrometry, and the structure determined by X-ray crystal-structure analysis, which supported a sandwich formulation. 

Mixed arene-2,5-dihydro-l,2,5-thiadiborole-iron complexes have been synthesized by a novel route thermally unstable bis(arene)iron sandwich complexes, prepared by cocondensation of iron atoms with arene, react in the temperature range of -100 to -60°C with free Et2C2B2Mc2S to form reactive intermediates that decom-... 

In addition to [Hg( -toluene)2-(GaCI/ )2],168 other mercury-arene complexes of general formula [I Ig( /2-arene)2-(AlCUy have been prepared.169 These include the bis(toluene), bis(o-xylene), and bis(l,2,3-trimethylbenzene) complexes 159, 160, and 161, respectively, whose structures have all been determined (Figure 8). While the arene in 159 and 161 is coordinated in an asymmetrical -fashion, the /2-1,2,3-trim ethylbenzene ligands of 160 form two nearly equal Hg-C bonds of 2.45 and 2.46 A. DFT calculations show that the Hg-arene interactions are mostly ionic. 

Fe-arene complexes have been employed for the same purposes as their Ru counterparts, namely, in the preparation of monomeric aryl ethers,463,486-488 polyaromatic ethers,489,490 and macrocyclic aryl ethers.491... 

Although several phenyl derivatives of the lanthanides and actinides have been characterized, only one re-arene complex of the / transition metals is known to date. This is the uranium(III) benzene complex, U(AlCl4)s CeHe 153), prepared by the combination of uranium tetrachloride, aluminum trichloride and aluminum powder in refluxing benzene, the Fischer-Hafner method [154). The molecular geometry of the complex is shown in Fig. 18. 

Two observations initiated a strong motivation for the preparation of indenylidene-ruthenium complexes via activation of propargyl alcohols and the synthesis of allenylidene-ruthenium intermediates. The first results from the synthesis of the first indenylidene complexes VIII and IX without observation of the expected allenylidene intermediate [42-44] (Schemes 8.7 and 8.8), and the initial evidence that the well-defined complex IX was an efficient catalyst for alkene metathesis reactions [43-44]. The second observation concerned the direct evidence that the well-defined stable allenylidene ruthenium(arene) complex Ib rearranged intramo-lecularly into the indenylidene-ruthenium complex XV via an acid-promoted process [22, 23] (Scheme 8.11) and that the in situ prepared [33] or isolated [34] derivatives XV behaved as efficient catalysts for ROMP and RCM reactions. 

Bis(Tj6-jV,-/V-dimethylaniline)molybdenum has been prepared in good yield by cocondensation of molybdenum atoms with a fifty-fold excess of Af,Af-dimethyl-aniline vapor on a liquid nitrogen cooled surface. This method has been extended to the synthesis of other molybdenum arene complexes and is at present the only synthetic route to such compounds. 

The synthetic potential of transition metal atoms in organometallic chemistry was first demonstrated by the formation of dibenzenechrom-ium (127). Apart from chromium, Ti, V, Nb, Mo, W, Mn, and Fe atoms each form well-defined complexes with arenes on condensation at low temperatures. Interaction has also been observed between arenes and the vapors of Co, Ni, and some lanthanides. Most important, the synthesis of metal-arene complexes from metal vapors has been successful with a wide range of substituted benzenes, providing routes to many compounds inaccessible by conventional reductive preparations of metal-arene compounds. 

The only route to dibenzenetitanium so far described is the reaction of titanium atoms with benzene the reductive routes that give access to arene complexes of Group V and VI metals fail for titanium. Although yields of about 30% are reported for the preparation of dibenzene-, ditoluene-, and dimesitylenetitanium, the reactions are more sensitive than most to the effect of excess metal. Unless the ligand-to-titanium ratio is high and the rate of deposition of titanium vapor kept low, the products seem to be catalytically decomposed by finely divided Ti metal 4a, 7). 

Molybdenum and tungsten atoms seem to react with alkylbenzenes more efficiently than chromium atoms yields of 30 to 50% are reported (113). Conventional routes to the synthesis of tungsten-arene complexes are difficult and inefficient so that the ability to prepare these compounds in high yield via tungsten atoms is of special significance. Unfortunately, tungsten has a very high vaporization temperature and the scale of work with its vapor is necessarily limited. 

A second synthetic procedure for preparing silylated arene complexes, based on the metalation of a preformed rj6-arene complex, followed by treatment with an organochlorosilane, has been used only in one case so far namely, bis(benzene)chromium (47) ... 

In principle, the preparative procedures for tethered arene complexes fall into four distinct classes, which are represented in over-simplified form in Scheme 1. The... 

A tridentate (r 6 ri1 r 1) strapped arene complex of ruthenium(II), 20, containing a pair of auxiliary nitrogen donor atoms derived from (R, R)-1,2-diphenylethylenedi-amine, has been prepared by a sequence in which the functionalized arene is first coordinated to ruthenium(II), as shown in Scheme 5.25 The structure of 20 has been... 

This approach, in which an arene appended to a coordinated donor atom replaces a labile ligand, is by far the most generally useful procedure and has been applied to the preparation of tethered arene complexes of Ti(IV), Cr(0), Mo(0), Mo(II), W(II), Ru(II), Rh(I), and Ir(I). The labile ligand itself is often an arene, as shown in Scheme lb, in which case the replacement is an intramolecular version of the intermolecular exchange between free and coordinated arenes, which has been studied for complexes of the type [M(CO)3(ri6-arene)] (M = Cr, Mo),26 31 [Ir(ri6-arene)(ri4-l,5-COD)]BF4,28 32 and [Ru(ri6-arene)(ri4-l,5-COD)]28 (COD = cyclooctadiene). 

A large number of strapped arene complexes of ruthenium(ll) have been prepared by treatment of [RuCl2(il6-arene)]2 complexes with tertiary phosphines of the type R2P Ar in which an aromatic group is separated from the phosphorus atom by a two- or three-atom chain. In the first step, which usually occurs at or just above... 

Displacement of a coordinated arene by a pendant arene (Scheme lb) has been used to prepare tethered arene complexes in which the auxiliary ligand is a carbene. 

Arene(chromium tricarbonyl complexes, preparation and properties, 5, 258 (Arene(chromium tricarbonyls... 

Arene-displacement reactions, characteristics, 1, 97 Arene-ene substrates, in C-H bond alkylation, 10, 218 Arene-ferracarboranes, characteristics, 3, 225-226 I // -Arene liruliiim complexes, preparation, 7, 388 (Arene)metal(diborolyl) sandwiches, synthesis, 3, 12... 

Bis(adamantylimido) compounds, with monomeric chromium(VI) complexes, 5, 348 Bis(alkene) complexes conjugated, Rh complexes, 7, 214 mononuclear Ru and Os compounds, 6, 401 -02 in Ru and Os half-sandwich rj6-arenes, 6, 538 with tungsten carbonyls and isocyanides, 5, 685 Bis(u-alkenylcyclopentadienyl) complexes, with Ti(II), 4, 254 Bis(alkoxide) nitrogen-donor complexes, with Zr(IV), 4, 805 Bis(alkoxide) titanium alkynes, in cross-coupling, 4, 276 Bis(alkoxo) complexes, with bis-Cp Ti(IV), 4, 588 Bis[alkoxy(alkylamino)carbene]gold complexes, preparation, 2, 288... 

Bis(phoshacyclopentadienyl)titanium(II) complexes, preparation and reactivity, 4, 265 Bisphosphanes on DIOP modification, 10, 7 in hydrogenations, 10, 7 in hydrogenations, P-chiral ligands, 10, 11 Bisphosphinidenes, with platinum(II), 8, 453 -54 Bisphosphinites, in hydrogenations, 10, 14 Bis(phosphinoalkyl-thioether)arenes, in ruthenium isocyanides, 7, 138... 

Iridium nanoparticles, preparation, 12, 82 Iridium(III) O-ligated complexes, preparation, 7, 315 Iridium polyhydrides, preparation and characteristics, 7, 405 Iridium pyrrolyl derivatives, reactivity, 7, 282 Iridium tetrahydrides, characteristics, 7, 407-408 Iridium trihydrides, preparation, 7, 405 Iridium vinylidenes, synthesis and characteristics, 7, 352 Iridium xyliphos complexes, properties, 7, 442 Iridoids, via Pauson-Khand reaction, 11, 360 Iron(arene) (cyclopentadienyl) cations, preparation and reactivity, 6, 166... 

Manganese allyl complexes, preparation, 5, 826 Manganese arenes, preparation and characteristics, 5, 830 Manganese aryl complexes, preparation and characteristics,... 

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