Aryl complexes metal hydroxides

As shown in this table, the metal catalysts used in the literature are mostly complexes of Ni or Cu and less often Co or Pd. For soft nucleophiles, on the left of the table, the efficiency of the nickel catalysts was already reported. Here, are presented the investigations concerning the arylation of hard nucleophiles such as amines, alcohols or hydroxide anion, using Ni, Pd and Cu catalysts. 

For most of the hydrolysis of esters or amides catalyzed by exchange-labile metal ions, whether the reaction involves attack by hydroxide ion on the metal-bound carbonyl group or attack by the metal-hydroxo ion at the unactivated carbonyl group is not clearly differentiated. In rare instances, the two mechanistic possibilities were resolved by kinetic methods as exemplified by the hydrolysis of an aryl ester catalyzed by a Zn(II) complex, which proceeds through the attack of (P) by an hydroxide ion at the metal-bound carbonyl group rather than attack of (Q) by the metal-bound hydroxide ion (55). 

The reaction of CO2 with a metal hydride produces formate complexes M-0C(0)H, not formyl derivatives M-C(0)0H, and the insertion into M-C bonds gives the appropriate carboxylate compounds M-0C(0)R. In a similar fashion, the reactions with M-OH and M-OR (R = alkyl, aryl) generate the corresponding bicarbonate M-0C(0)0H and carbonate M-0C(0)0R species, respectively. The reaction of CO2 with a zinc hydroxide moiety is particularly important in biological systems, namely, for the reversible hydration of CO2 to HCOs catalyzed by Zn(ll) in carbonic anyhdrases. Moreover, it has been postulated that the insertion of CO2 into M-O bonds is essential in the co-polymerization of CO2 and epoxides and in the preparation of cyclic carbonates and polycarbo-In a similar vein, the insertion of CO2 into the M-N bond of both main group and transition metal... 

Imidazolium salts are precursors (preligands) of carbene ligands. In several cases, they can be directly submitted to the formation of metal complexes. Various approaches for the synthesis of imidazolium salts of types 1 and 2 are reported in the literature (Scheme 2.151) [23]. The most common synthesis of 1 is based on the Af-alkylation of l//-imidazole with alkyl halides in the presence of bases (sodium hydride, sodium or potassium hydroxide, or potassium tert-butoxide, route A). 1-Substituted imidazoles, usually Al-methylimidazol, are convenient starting materials to generate nonsymmetric imidazolium salts of type 1 by treatment with a second equivalent of alkyl or aryl halide [25]. 

The strong cr-donating ability of the alkynyl unit that is capable of raising the energy of the LF excited states, together with the interest in metal alkynyl systems, has led to the synthesis of the first series of luminescent alkynyl complexes of platinum]ii) terpyridine, [Pt]trpy)C=C-R], which was reported by Yam and coworkers [156]. The complexes were prepared in reasonable yields by reacting the platinum]ii) terpyridyl complex, [Pt]trpy)]NCMe)]]OTf)2, with various aryl-alkynes in the presence of sodium hydroxide or triethylamine in methanol [Scheme 10.20). 

Haloform reactions are generally performed with halogens in the presence of hydroxide [251] or directly with hypohalites [252]. Alternative methods affording carboxylic acids from methyl ketones (or other enolizable substrates) include the aerobic oxidation in the presence of a catalytic amount of dinitrobenzene [253] with a base in a dipolar aprotic solvent such as DMF [254] or HMPT (hexamethylphospho-ric triamide) [255, 256] and the use of stoichiometric quantities of hypervalent iodide derivatives [95, 257] or nitrosylpentacyanoferrate [258]. Furthermore, metal catalysts can be used, and systems such as tert-butyl hydroperoxide in the presence of rhenium oxide [259], oxygen in combination with a copper complex [260], heteropolyacids [261] and Mn"/Co" systems [262] were found to be applicable. Finally, aryl ketones are selectively oxidized to aliphatic carboxylic acids by treatment with periodate [81] in the presence of ruthenium trichloride [263]. 

---