Imidazoles biimidazoles

Syntheses and Properties of Coordination Complexes of Imidazole Types. Mao, Qing Lin, Zhamu (School Pharmacy, West China University Medical Sciences, Chengdu, Sichuan, Peop. Rep. China 610066). Sichuan Shifan Daxue Xuebao, Zirun Kexueban 1998, 21 (4), 436-440 (Ch.), Sichuan Shifan Daxue. The authors have reported three types of coordination complexes of imidazole with Cu, Co and Ni which were synthesized from imidazole, biimidazole and transition metal acetate. Their properties were systematically characterized by TGDK IR, Co-y irradn., XPS and EPR. 

Biimidazole and bibenzimidazole with [(ri -2-RC3H )Pd(p-Cl)]2 (R = H, Me) taken in the 2 1 molar ratio in the presence of methanolic potassium hydroxide give complexes of the type 146 (83JCS(D)1729) and with [(ti -2-RC3H ) Pd(Mc2C0) ](C10 ) - 147. When the ratio of 2,2 -biimidazole or 2,2 -bibenz-imidazole and [(Ti -2-RC3H )Pd(p-Cl)]2 (R = H, Me) is 1 1, the homo-tetranuclear species 148 result. Heterotetranuclear palladium(II)-rhodium(I) complexes 149 (L2 = cod) follow from [(TiLcod)Rh(Hbim)] and [(ri -2-R-C3H )Pd(acac)]. They are readily carbonylated with complete substitution of... 

Imidazole is characterized mainly by the T) (N) coordination mode, where N is the nitrogen atom of the pyridine type. The rare coordination modes are T) - (jt-) realized in the ruthenium complexes, I-ti (C,N)- in organoruthenium and organoosmium chemistry. Imidazolium salts and stable 1,3-disubsti-tuted imidazol-2-ylidenes give a vast group of mono-, bis-, and tris-carbene complexes characterized by stability and prominent catalytic activity. Benzimidazole follows the same trends. Biimidazoles and bibenzimidazoles are ligands as the neutral molecules, mono- and dianions. A variety of the coordination situations is, therefore, broad, but there are practically no deviations from the expected classical trends for the mono-, di-, and polynuclear A -complexes. 

The biphenyl ligand functionalized with two imidazoles (6) was used to produce distorted tetrahedral complexes of zinc.119 2,2 -Biimidazole can act as a bidentate ligand coordinating to one zinc ion (7) or as a bridging ligand in the formation of dimeric species (8) with X-ray structures of both binding motifs.120... 

Replacement of both pyridine rings of bipyridine by imidazole has a much greater effect than replacement by thiazole and the [Fe N6]2+ derivative of 2,2 -biimidazole 34 (Dq(Ni2+)=1080 cm-1) is purely high spin [41]. The spin-crossover behaviour of tris(2,2/-bi-imidazoline)iron(II) salts seems somewhat unexpected in light of this and the relatively low a-donor power as indicated by the small Dq(Ni2+) value (1030 cm-1) for 36. 

Whereas the synthesis of 2,2 -biimidazoles has been very well developed, that of 4,4 -biimidazoles has not. Pyne et al. revealed that the Pd(0)-catalyzed homocoupling of 4-iodo-l-(triphenylmethyl)imidazole (5a) or its 2-methyl analog 5b delivered the 4,4 -biimidazoles 6a and 6b, respectively [6],... 

Note. Abbreviations used imH, imidazole imFL, neutral imidazolium ylide (deprotonated at C-2) glyglyhis, glycylglycyl-L-histidine bzimH, benzimidazole biimH2, 2,2 -biimidazole pyzH, pyrazole pz, pyrazine pzH, pyrazinium monocation 4-pic, 4-picoline isn, isonicotinamide py, pyridine 4-acpy, 4-acetylpyridine dmpzH. 2,6-dimethylpyrazinium monocation 4,4 -bpyH, 4,4 -bipyridinium monocation. T = 25°C unless otherwise stated. 

In time, HABIs were to become important components of photopolymer systems as of December 2004, there were over 1000 U.S. patents, in which biimidazoles, lophine dimers, HABIs, and 2-o-chlorophenyl-imidazole derivatives were mentioned A word about patents. At Du Pont, the names of inventors are listed alphabetically, even though the lead inventor might have a name that was at the bottom of the alphabet. There were exceptions. Sometimes, one of the inventors would request the attorneys to list a lead inventor first. 

The N-bonded imidazolate monoanion forms bridges. Biimidazoles can act as mono-or dianion, for example, in the complexes... 

The polymer is soluble in polar aprotic solvents such as N-methyl pyrrolidinone and in aqueous base. The solubility in base is due to deprotonation of the acidic hydrogen at the 1-position of the imidazole ring. In imidazoles, the pKa of the 1-nitrogen is approximately 14, but in cyanoimidazoles the pKa of this position ranges from 2 (in 4,4, 5,5 -tetracyano-2,2 -biimidazole) to approximately 9-10 in monocyano substituted imidazoles [5]. The acidity of this position provides a handle for solution processing or for chemical modification of the polymer. 

Tetrakis(imidazole)dinitratocopper(II), 42B, 825 Cl2H1gN20eZn, Zinc picolinate tetrahydrate, 40B, 1126 Cl2H1gNioNiOe, Diaquo-bis(2,2 -biimidazole)nickel(II) nitrate, 34B, 569... 

Unfortunately, only patents issued after 1975 can be searched electronically and searching for chemical structures is complicated by the fact that trivial names abound. In compiling a database for HABIs, I found different patents which identified lophine dimers, imidazole dimers, imidazolyl dimers, DYLUX , bisimidazoles, biimidazoles, etc. 

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