1-Methylimidazole adduct

X-Ray studies of crystals of pyridine complexes with trimethylsilyl bromide and iodide (264) and of N-methylimidazole adducts to trimethyl-chlorosilane (265) were performed. The tetracoordinate silicon structure of these complexes was proved. The distances between the halogen and silicon atoms in pyridine adducts are 4.359 and 4.559 A for bromine and iodine, respectively, which is approximately 2 A greater than the sum of the covalent radii and significantly longer (0.5 A) than the sum of the van der Waals radii. This result is consistent with the ionic structures of the complexes in the solid state. The distance from silicon to nitrogen (1.86 A) is evidently larger than the length of typical Si—N bonds (1.75 A), which... 

M. 5- 3,4-CATECHOLATO[HYDROTRIS(3,5-DIMETHYL-l-PYRAZOLYL)BORATO]OXOMOLYBDENUM(V) -10,15,20-TRI-p-TOLYLPORPHINATOIRON(III)BIS(A-METHYLIMIDAZOLE) ADDUCT Fe(A-MeIm)2[(3,4-Mo-TTP)]CL ... 

Figure 10 Three views of the Co-02 adduct of (261), with a disordered N-methylimidazole as the sixth ligand (reproduced with permission of the American Chemical Society from Inorg. Chem., 1994, 33, 910-923).

The metal ion, e.g. Fe or Co, when in its lower oxidation state can share electron charge with the oxygen molecule adduct. Several iron and cobalt prophyrin derivatives and cobalt-Schiff bases show the necessary reversibility and rates for successful application [e.g. 23]. a, a, a", a" -weso-tetrakis[(o-piralamidophenyl)-po phinato] Co (II) has been complexed with 1-methylimidazole to make a complex (CoPIm) which, when mixed with polybutyl methacrylate gave oxygen permeabilities on the order of 10-9 sec-cm/(cm2-s-cmHg) with a selectivity of about 5 over nitrogen [23]. 

An unexpected reaction occurs when 2-alkyl-4(5)-nitroimidazoles (27 R = alkyl) are reduced in protic solvents [92JCS(P1)2779]. Catalytic hydrogenation of 2-methyl-4(5)-nitroimidazole (27 R = Me) in a solution of acetic anhydride and acetic acid gave 4,4 -diacetamido-2,2 -dimethyl-5,5 -diimidazole (32 yield 10%) in addition to the expected 4-acetamido-l-acetyl-2-methylimidazole (28%). Similarly, reduction of the 2-alkyl-4(5)-nitroimidazoles (27 R = Me, Et, iPr) in ethanol solution in the presence of diethyl ethoxymethylenemalonate [EMME (135)] gives predominantly the 5,5 -diimidazole adducts (33). The formation of these products (33) is believed to involve an electrophilic addition of the starting material (27) to the electron-rich aminoimidazoles (25) [92JCS(P1)2779]. Interestingly, replacement of ethanol by dioxane suppressed diimidazole formation. 

Generally, the intermolecular Heck reaction between 2-iodo-, 4-iodo- and 5-iodo-l-methylimidazoles and olefins suffers from low yields (< 25%). Therefore, these transformations are of limited synthetic utility [29]. In one case, variable yields for adduct 62 (15-58%) were observed for the Heck reaction of 5-bromo-l-methyl-2-phenylthio-lf/-imidazole (61) and a large excess of methyl acrylate [42]. 

Although the kinetics of imidazole exchange between NP2 and its low-spin imidazole adduct are very slow and no chemical exchange cross peaks in the NOESY/EXSY spectrum of a mixture of the high-spin and low-spin forms of NP2 are observed, the V-methylimidazole complex... 

Since the formation of the isoguanine derivative 88 has been proved to occur via the intermediacy of 4-ureido-5-cyano-l-methylimidazole (87) (having as precursor the C-2 adduct), its formation can thus be described as oc-... 

Recently, the Anson group sought to find the elusive Co—O2 adduct that is supposedly formed as an intermediate for the electron-transfer reaction [100]. A 1-methylimidazole-substituted picket fence porphyrin was chosen due to its high affinity for molecular oxygen. Unfortunately, the desired adduct was not observed instead, the four-molecule picket appended to one side of the porphyrin ring actually hindered the catalytic reduction of molecular oxygen. 

In (67 R1 = R2 = Me, R = H) with X = Br green or yellow complexes were obtained, according to the solvent used, with v(V=0) at ca. 980 and 900 cm-1, respectively.748 When X = C1, only the green-type complex may be obtained. The authors assume five-coordinate square pyramidal geometry for the green complexes and a chain structure -V=0 V=0 , similar to [VO(salnpn)], for the yellow complex. Solid adducts were isolated with 1-methylimidazole. 

Mononuclear complex formation was confirmed for the adduct of zinc(II) salt with 2-mercaptobenzothiazole and o-phenanthroline (253). The t/-S coordination is observed in the complexes of triphenylphos-phine gold with 2-mercapto-l-methylimidazole (254) (88JOM119), 8-mercaptotheophilline (255) (91IC3743), 2-mercaptobenzoxazole (256) [94AX(C)1420], and purine-6-thiol (257) (94AJC577). 

The reaction of t with 1-methylimidazole is reported by Kaupp and Gunter (136) to yield the addition product 77. Unlike the reaction of It with 1-methylpyrrole, the formation of 77 does not require acid catalysis. The formation of 77 is proposed to occur via the 1,2-biradical intermediate 78, which undergoes a 1,3-hydrogen atom migration to yield 77 (eq. 27). The reaction of It with benzothiazole also yields an acyclic adduct 79 and a second adduct 80 as the major products. Both 79 and 80 are proposed to arise via a 1,4-biradical intermediate similar to 78. Irradiation of t-1 with caffeine (81) yields a [2+2] cycloadduct 82 and an acyclic adduct 83, analogous to 80, as the major products. 

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