O-Metallation reaction

The syntheses of phenyldiimide complexes have been reported by Toniolo and coworkers.451 One example is the o-metallation reaction of the aryldiazenato iridium(III) complex (202) with pheny-lacetylene (reaction 115) to yield complex (203). 

The use of acetic acid as solvent promotes the second ort/io-metalation step. Thus after 1 h of reaction of rhodium acetate and P(o-BrCsF4)Ph2, two new products, 5 and 6 were obtained in addition to the previously described compounds 3 and 4. This was the first direct evidence that acetic acid catalyzes the ort/ o-metalation reaction. Both 5 and 6 are bimetalated Rh(II) dimers. Compound 6 has a close structural resemblance to 1, with two metalated ligands. In this case the PCBr ligands assume an, / -mode of ligation. In 5 one of the axial positions was found to be occupied by a molecule of water. P NMR spectroscopy of the reaction mixture shows that this site is initially occupied by a molecule of acetic acid which is displaced by water during the subsequent chromatography. 

Table 3 Activation parameters for the oxX o-metalation reaction c /[IrClXMe(PPh3)2] (from ref 36)...

The reaction of 34 with triethylethylidenephosphorane is more complex. According to the multinuclear NMR data, the reaction occurs at the 1 2 ratio of the reactants. The Sn-O bond is cleaved to give phosphonium phenoxide (38) and stannylene (37) in which the tin atom is also bound to the ylide carbon atom of phosphorane (Scheme 17).61 Metallation reactions of this type are well known.61,75... 

This procedure is more convenient than the conventional method, which involves a trans-metalation reaction from an o -alkoxyalkyltrialkyltin(IV). 

The controlled synthesis of carbons adjacent nido- and arachno-carborane anions can be achieved by the reduction of C (cage)-C (cage)-linked o-carboranes with group 1 metals.234-237 Typical examples are illustrated in Scheme 22. These have been found to undergo metallation reactions similar to their carbons apart analogs, forming full- and half-sandwich complexes of lanthanide metals.238... 

For metal electrodes, the anodic 03Q n reaction proceeds at electrode potentials more anodic than the equilibrium potential Bo of the reaction as shown in Fig. 10-14. For n-type semiconductor electrodes, the anodic photoexdted oxygen reaction proceeds at electrode potentials where the potential E of the valence band edge (predsely, the potential pEp of the quasi-Fermi level of interfadal holes, pCp = — CpEp) is more anodic than the equilibrium oxygen potential Eq, even i/the observed electrode potential E is less anodic than the equilibrium oxygen potential E03. The anodic hole transfer of the o Qgen reaction, hence, occurs at photoexdted n-type semiconductor electrodes even in the range of potential less anodic than the equilibriiun potential Eq of the reaction as shown in Fig. 10-14. 

It is well established that metallic copper or copper salts efficiently catalyze N- and O-arylation reaction using pentavalent and trivalent organobismuth compounds [5-9, 24]. The C-arylation reaction of phenols and active methylene compounds using pentavalent organobismuth compounds are usually mediated by a base. However, in some cases, copper catalysts mediate C-arylation using pentavalent organobismuth compounds. 

Speromagnetism (Fig. 6.5 d) is a property of some amorphous or poorly ordered materials containing metal-O-metal bonds which, if the metal carries a magnetic moment, can support super-exchange reactions (Coey Readman, 1973). 

Felhnann and Dubois have described the structure of the enolate 29 derived from the reaction of f-butyl acetate with (MeO)2Mg. The NMR spectrum reveals two O-metallated species, which should be symmetric enolates as proposed by Pinkus and Wu for the bromomagnesium enolate of methyhnesityl ketone (metal is tricoordinated). ... 

As broadly demonstrated in aromatic DoM chemistry (90CRV879), iterative metalation of pyridyl O-carbamates are synthetically useful processes. Thus, sequential metalation reactions of 3- and 4-pyridyl O-carbamates with electrophiles that provide incipient DMGs afford 3,4,5-trisubstituted pyridines 327, 328, and 329, respectively (Scheme 99) (85JOC5436). 

Butylene isomers also can be expected to show significant differences in reaction rates for metallation reactions such as hydroboration and hydroformylation (addition of HCo O). For example, the rate of addition of di(jw-isoamyl)borane to oy-2-butene is about six times that for addition to //r7/ j -2-butene (15). For hydroformylation of typical 1-olefins, 2-olefins, and 2-methyl-1-olefins, specific rate constants are in the ratio 100 31 1,... 

Regiospecific synthesis of naphthols.1 The o-allylbenzamide 1, obtained by directed o-metallation of tertiary amides (12,97-99, and previous references cited), on treatment with CH3Li (superior to LDA, sec-BuLi) cyclizes to the naphthol 2. This reaction provides an attractive route to naphthoquinones (equation I). 

Many metal / -diketonates are coordinatively unsaturated and reactions with Lewis bases to form complexes are a pervasive feature of their chemistry.14 In previous sections, base cleavage of M—O—M bridge bonds in oligomeric acetylacetonates and formation of hydrated lanthanide dike-tonates having high, odd coordination numbers have been noted. Mechanistically, acid-base complexes are quite likely to be involved in hydrolysis, displacement and ort/zo-metallation reactions, albeit that the interactions may be weak. 

Reaction CLXIX. Action o Metals on Nitro Compounds in Acid Media. 

The intrinsic nature of tungsten carbide catalyst in CO-H2 reactions is to form hydrocarbons. This property can be modified by oxidic promoters as for the case of noble metals like Pt or Rh or by the presence of carbon vacancies at the surface. To increase the production of alcohols in the Fischer-Tropsch reaction, the catalyst should be bifunctional, with oxidic and carbidic components as in the case of WC on Ti02. Overcarburization of WC on supports like Si02 or Zr02 where the W-O-metal interaction is weak leads to C/W ratios close to unity and does not result in alcohol formation. 

Highly stereoselective aldol reactions of lithium ester enolates (LiCR1 R2CC>2R3) with (/0-2-(/ -tolylsulfiny I (cyclohexanone have been attributed to intermediacy of tricoordinate lithium species which involve the enolate and the sulfinyl and carbonyl oxygens of the substrates.43 The O-metallated /<-hydroxyalkanoatcs formed by aldol-type reaction of carbonyl compounds with enolates derived from esters of alkanoic acids undergo spontaneous intramolecular cyclization to /1-lactones if phenyl rather than alkyl esters are used the reaction has also been found to occur with other activated derivatives of carboxylic acids.44... 

The 1,2,3,5,6-pentathiepane was used for synthesis of metal complexes with platinum(O). The reaction of the... 

Figure 5.3 Synthetic conditions for the mixed-ligand Pc complexes, containing one Pc ligand. Route 1 interaction of o-dicyanobenzene(s) and their analogues with lanthanide salts. Route 2 metallation reaction of the macrocyclic ligand or its dianione by lanthanide compounds. Route 3 reactions of axial substitution in the environment of the central atom in lanthanide complexes ([96] and references cited therein). (From Ref. 96, with permission.)...

The acidity of the hydroxyl group can be seen in the rapid proton-deuteron exchange that can take place when alcohols are dissolved in D O (Reaction I), alkali metals (Reaction II) and organometallic reagents (Reaction III and IV). 

Directly supported clusters of type Os3H(CO)10(O—metal oxide) break down at quite low temperatures to give species which have a high selectivity to methane from CO and H2 (381,400). Similar behavior has been reported for Os3(CO)12 itself (401), but it is difficult to rule out metal as the catalyst. Os3(CO)12 also leads to methanol, methyl and ethyl formate, and acetone by reaction with CO and H 2 (190° C, 180 atm) in glyme solvents (402). The water-gas-shift reaction is catalyzed by Os3(CO)12, using KOH or even sodium sulfide in methanol as the base (403), although ruthenium catalysts are better (404). 

A preliminary account of the reaction of the ligand 1-benzoyliminopyridinium betaine (L = C5H5NNCOPh) with transition metals includes the isolation of a compound formulated as [Rh(L —H)2(H20)2]C1.199 1H N.m.r. and i.r. evidence indicates o-metallation of the phenyl ring, causing the betaine to function as a bidentate ligand via an o-carbon of the phenyl ring and the imino-N atom. 

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