Aryldiazonium complexes

Free carbenes based on 1,2,4-triazole are not as numerous as those based on imidazole (70ZN(B)1421, 95AGE1021, 97JA6668, 98JA9100). The carbene complex 169 (Ar = Ph, p-Tol) is prepared by the [3 + 2] cycloaddition route from [W(CO)j(C+=NC-HCOOEt)]- and aryldiazonium (930M3241). Oxidative decomplexation causes tautomerization of the 1,2,4-triazole ligand, the products being 170 (Ar= Ph, i-Tol). 

Coordination chemistry of aryldiazonium cations aryldiazcnato (arylazo) complexes of transition metals and the aryldiazenato-nitrosyl analogy. D. Sutton, Chem. Soc. Rev., 1975, 4, 443-470 (89). 

As mentioned in the discussion of the reaction mechanism for this transformation, the active species is a dicoordinate Pd(0) complex, and it is unclear whether an associative or a dissociative process is operative for oxidative addition. In this context, different NHC complexes containing only one carbene ligand have been tested in the Mizoroki-Heck reaction. The most successful are those prepared by Beller, which were able to perform the Mizoroki-Heck reaction of non-activated aryl chlorides with moderate to good yields in ionic liquids (Scheme 6.13). The same compounds have also been applied to the Mizoroki-Heck reaction of aryldiazonium... 

Insertion of mono- or bis(aryldiazonium) cations into the Re—bonds of the hydride complexes [ReH(CO)5 (PR3)J (PR3 = P(OEt)3, PPh(OEt)2, PPh2(OEt) =1 ) results in the formation of cationic aryldiazene complexes of the compositions [Re(HNNAr)(CO)5 (PR3) ]" or [ Re(CO)5 (PR3) 2(/r-HNNArNNH)] +. " Bifunctional diazene/diazonium derivatives which can be prepared in this way are excellent building blocks for heterobinuclear and heterotrinuclear compounds with bis(aryldiazene) bridging ligands as has been demonstrated for Re-Ru, Re-Os,... 

Three methods are commonly employed for the in situ preparation of organopalladium derivatives (i) direct metallation of an arene or heterocyclic compound with a palladium(II) salt (ii) exchange of the organic group from a main group organometallic to a palladium(II) compound and (iii) oxidative addition of an organic halide, triflate or aryldiazonium salt to palladium(O) or a palladium(O) complex. 

Deprotonation of some molybdenum-carbyne complexes affords vinylidene derivatives suitable reagents are aryldiazonium salts, trifluoroiodo-methane 34), or n-butyllithium (55) ... 

In sum, the cupric ion transfers an electron from the unsaturated substrate to the diazo-nium cation, and the newly formed diazonium radical quickly loses nitrogen. The aryl radical formed attacks the ethylenic bond within the active complexes that originated from the [aryldiazonium tetrachlorocuprate(II)-olefin] or [initial arydiazonium salt-catalyst-olefin] associate and yields the >C(Ar)—C < radical. The latter was detected by ESR spectroscopy. The formation of both the cation radical [>C=C<]+ and the radical >C(Ar)—C < as intermediates indicates that the reaction involves two catalytic cycles. In the other case, the radical >C(Ar)—C < will not be formed, being consumed in the following reaction ... 

The reaction of [RhHCl2(PPh3)3] with aryldiazonium salts in the presence of LiCl gives complexes that were originally formulated as solvated rhodium arylazo complexes (21), but these have subsequently been shown by H NMR and 15N-labeling studies to be the diazene complexes RhCl3(NHNAr)(PPh3)2] (218). 

The only example to date of the insertion of an aryldiazonium ion into a metal-hydrogen bond to yield a hydrazido(2-) complex is that shown in Eq. (34) (66, 67). 

Aryldiazonium salts are weak electrophiles. Consequently, they undergo Ar-SE reactions via sigma complexes (azo couplings) only with the most strongly activated aromatic compounds. Only phenolates and secondary and tertiary aromatic amines react with them. Primary aromatic amines react with diazonium salts, too, but via their N atom. Thus, triazenes, that is, compounds with the structure Ar—N=N—NH—Ar are produced. Phenol ethers or nonde-protonated phenols can react with aryldiazonium salts only when the latter are especially good... 

Reaction of [Ru(porph)CO] (porph = mew-porphyrin IX dimethyl ester) with NO in benzene yields [Ru(porph)(NO)2], vN0 - 1786 and 1838 cm-1.2589,2590 [Ru(OEP)(CO)py] with NO in MeOH affords [Ru(OEP)(OMe)NO].2572 The aryldiazonium adducts [Ru(porph)(N2Ar)solvent]+ (porph = TPP, Ar = Ph, 4-MeOPh, solvent = acetone porph = TPP, Ar = 4-N02Ph, solvent = EtOH porph = OEP, Ar = 4-N02Ph, solvent = EtOH) have been prepared by reaction of [Ru(porph)(CO)(HOEt)] with ArN2+ in refluxing CH2C12.2618 The stretching vibration vN=N occurs near 1800 cm-1 for these complexes.2618... 

Introduction.—Reviews on the molecular structure of co-ordination compounds and organometallic compounds containing molybdenum and tungsten as determined by X-Tdiy diffraction have appeared. Structural aspects of Mo , Mo, and Mo complexes have been examined and molybdenum complexes themselves have also been specifically reviewed. A discussion of molybdenum and tungsten dialkyl-amides and disilylamides has been included in a recent review and the co-ordination chemistry of aryldiazonium cations (ArNj) of molybdenum and tungsten has been discussed. ... 

Photoinitiated cationic polymerization has been the subject of numerous reviews. Cationic polymerization initiated by photolysis of diaryliodonium and triarylsulfonium salts was reviewed by Crivello [25] in 1984. The same author also reviewed cationic photopolymerization, including mechanisms, in 1984 [115]. Lohse et al. [116], reviewed the use of aryldiazonium, diphenyliodonium, and triarylsufonium salts as well as iron arene complexes as photoinitiators for cationic ring opening polymerization of epoxides. Yagci and Schnabel [117] reviewed mechanistic studies of the photoinitiation of cationic polymerization by diaryliodonium and triarylsulfonium salts in 1988. Use of diaryliodonium and sulfonium salts as the photoinitiators of cationic polymerization and depolymerization was again reviewed by Crivello [118] in 1989 and by Timpe [10b] in 1990. 

The chlorophosphonium complexes 39, produced (Scheme 8) during the synthesis of cyclic esters of arylphosphonic acids from aryldiazonium tetrafluoroborates and cyclic chlorophosphites, are decomposed by H2S to give the analogous esters of arylthiophos-phonic acids ... 

Brown and Doyle have studied the reduction of aryldiazonium ions. Two mechanisms are possible. The reduction could occur via a one-electron transfer non-bonded outer-sphere mechanism where an electron is transferred from a reducing agent to the diazonium ion or via a bonded inner-sphere mechanism, where an intermediate complex undergoes homolytic cleavage (equations 52 and 53), respectively. 

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