Alkoxo complex

since the benzylic C-H bond of the substituent in the chloride complex is activated by the strong base NaOR [45a]. 

---

Cinellu, M.A. and Minghetti, G. (2002) Gold(l) and gold(lll) complexes with anionic oxygen donor ligands hydroxo, 0X0 and alkoxo complexes. Gold Bulletin, 35, 11. 

Cinellu, M.A., Minghetti, G., Pinna, M.V., Stoccoro, S., Zucca, A., Manassero, M. and Sansoni, M. (1998) X-Oxo and alkoxo complexes of gold(III) with 6-alkyl-2,2 -bipyridines. Synthesis, characterization and X-ray structures. Journal of the Chemical Society,... 

Before discussing the preparation of late transition metal complexes resulting from the activation of O-H bonds by late transition metal complexes, we wbl describe metathesis methods for the preparation of hydrido(hydroxo), hydrido(alkoxo), and hydrido(carboxylato) complexes. Though many methods of preparation of transition metal hydroxides, alkoxides, etc. by a metathesis reaction have been reported [1], only a limited number of examples of the preparation of hydrido(hydroxo), hydri-do(alkoxo) complexes etc. by metathesis are available. 

Complexes Resulting from Activation of Alcohols Hydrido(alkoxo) Complexes... 

Hydrido(alkoxo) complexes of late transition metals are postulated as intermediates in the transition metal-catalyzed hydrogenation of ketones (Eq. 6.17), the hydrogenation of CO to MeOH, hydrogen transfer reactions and alcohol homologation. However, the successful isolation of such complexes from the catalytic systems was very rare [32-37]. 

The detailed decomposition (P-H ehminahon) mechanism of the hydrido(alkoxo) complexes, mer-crs-[lr(H)(OR)Cl(PR 3)3] (R = Me, Et, Pr R = Me, Et H trans to Cl) (56, 58, 60), forming the dihydrides mer-cis-[lr H)2Cl PR )2] (57, 59) along with the corresponding aldehyde or ketone was examined (Scheme 6-8). The hydrido(ethoxo) as well as the hydrido(isopropoxo) complexes 60 could also be prepared by oxidative addition of ethanol and isopropanol to the phosphine complexes 39 [44]. In the initial stage of the P-H elimination, a pre-equiUbrium is assumed in which an unsaturated pentacoordinated product is generated by an alcohol-assisted dissociation of the chloride. From this intermediate the transition state is reached, and the rate-determining step is an irreversible scission of the P-C-H bond. This process has a low... 

The formation of the first osmium hydrido(alkoxo) complex, a yellow air-stable and thermally stable hydrido(methoxo)osmium(II) complex, trans-[OsH(OMe)(Cl) (NO) (P Pr3)2] (72), by the oxidative addition of MeOH to a 16-electron complex, trans-[OsCl(NO)(P Pr3)2] (71) was briefly reported (Eq. 6.22) [51]. 

Recently, Y. Yamamoto reported a palladium-catalyzed hydroalkoxylation of methylene cyclopropanes (Scheme 6-25) [105]. Curiously, the catalysis proceeds under very specific conditions, i.e. only a 1 2 mixture of [Pd(PPh3)4] and P(o-tolyl)3 leads to an active system. Other combinations using Pd(0 or II) precursors with P(o-tolyl)3 or l,3-bis(diphenylphosphino)propane, the use of [Pd(PPh3)4] without P(o-tolyl)3 or with other phosphine ligands were all inefficient for the hydroalkoxylation. The authors assumed a mechanism in which oxidative addition of the alcohol to a Pd(0) center yields a hydrido(alkoxo) complex which is subsequently involved in hydropal-ladation of methylenecyclopropane. 

For example gold(III) complexes with /3-diketonates or alkylsiloxydes, are likewise employed as precursors for CVD. 73,177 Another promising result in the field of homogeneous catalysis is the discovery that gold(III) alkoxo complexes promoted the condensation of benzaldehyde with compounds containing an active methylene group.1775... 

Gold(III) alkoxo complexes are stabilized by a variety of ancillary ligands. Some of them, as with [Au2(/u-OTMS)2Me4] which was synthesized some time ago178"1 have found recent applications as precursor for CVD.1785 Thermally stable aryloxo and fluoroalkoxo complexes of the type... 

These alkoxo complexes are also capable of cleavage of the C—Si bond of TMSCF3. The gold(III) fluoroalkoxides m-[AuMe2(OR)(PPh3)] (R = CH2CF3, CF1(CF3)2) can act as catalysts for the Knoevenagel condensation reaction.1775... 

For rhodium and iridium compounds alkoxo ligands take over the role of the basic anion. Using /z-alkoxo complexes of ( -cod)rhodium(I) and iridium(I)— formed in situ by adding the /r-chloro bridged analogues to a solution of sodium alkoxide in the corresponding alcohol and azolium salts—leads to the desired NHC complexes even at room temperature [Eq. (10)]. Using imidazolium ethoxyl-ates with [(r " -cod)RhCl]2 provides an alternative way to the same complexes. By this method, it is also possible to prepare benzimidazolin-2-ylidene complexes of rhodium(I). Furthermore, an extension to triazolium and tetrazolium salts was shown to be possible. ... 

Several bis(/i-alkoxo) complexes have been reported for various pentadentate ligands. Some examples are [Mn2(2-0H-3-N02-SALPN)2] 2DMF (160-DMF),"" [Mn2(2-0H-5N02-... 

RuCljCHmpi) (Hmpi=l,3-bis(4-methyl-2-pyridylimino)isoindoline) is made from (Hmpi) and RuClj. As RuCl3(Hmpi)/02/2,6-lutidine or Na(OEt)/25-90°C it oxidised ethanol, 1-propanol and 1-butanol to the aldehydes and 2-propanol and 2-butanol to the ketones. A Ru(IV) alkoxo complex may be formed (e.g. Ru CljCmpiXOC Hj)), which then reacts with another mole of ethanol to give Ru CX(Hmpi)(C2HjOH) and CH3CCHO [793],... 

Mixed-ligand complexes of the type Ni(OR)L (L = deprotonated ancillary ligand) are formed when l-amino-2-ethanol, /3-diketones or carboxylic acids are reacted with bis-alkoxo complexes.1490-1492... 

Alkoxo-amino complexes, in Ru and Os half-sandwich rf-arenes, 6, 524-525 Alkoxo complexes... 

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... 

Cyclopentadienones, in molybdenum carbonyls, 5, 451 Cyclopentadienyl alkenes, with niobium, 5, 76 Cyclopentadienyl-alkoxo complexes, with Ti(IV), 4, 495 Cyclopentadienyl alkyl complexes, with niobium, 5, 66 Cyclopentadienyl-amido complexes, with Ti(IV), via dehalosilylation, 4, 448... 

Indanes, chromium tricarbonyl complexes, 5, 246 Indazoles, in copper-catalyzed lead reactions, 9, 409 Indenes, chromium tricarbonyl complexes, 5, 246 Indenide derivatives, alkali compounds, 2, 13 Indenones, via imine carbonylation, 10, 136 Indenyl-alkoxo complexes, with Ti(IV), 4, 500 Indenyl-amido complexes, with Ti(IV), 4, 454 Indenyl-amido dimethyl complexes, with Ti(IV), 4, 442 Indenyl bridges, in [Pg.126]

---