Iodine complex compounds, with pyridine

Perchlorates are unusual in that most are either extremely soluble or only sparingly soluble in water. Silver (I) perchlorate is one of the most soluble salts known, while its coordination compound with pyridine is so insoluble that pyridine can be precipitated quantitatively from aqueous solution by treatment with silver (I) perchlorate.1 Although several complexes of pyridine and silver (I) perchlorate have been described,1,2 the one in which silver(I) exhibits its common coordination number of two is the most stable. This compound provides a stable, nondeli-quescent starting material for synthesizing the perchlorates of the dipyridine complexes of unipositive bromine3 and iodine.4... 

The chromium carbonyl linkers 1.40 (98) and 1.41 (99) were prepared from commercial triphenylphospine resin and respectively from pre-formed p-arene chromium carbenes and Fischer chromium amino carbenes. Their SP elaboration is followed by cleavage with pyridine at reflux for 2 h (1.40) and with iodine in DCM for 1 h at rt (1.41) both linkers produce the desired compounds in good yields. A similar cobalt carbonyl linker 1.42 (100) was prepared as a mixmre of mono- (1.42a) and bis- (1.42b) phosphine complex, either from pre-formed alkyne complexes on triphenylphosphine resin or by direct alkyne loading on the bisphosphine cobalt complex traceless cleavage was obtained after SP transformations by aerial oxidation (DCM, O2, hp, 72 h, rt) and modified alkynes were released with good yields and... 

Positive halogen complexes with pyridine bases are known as versatile halogenating reagents. Bis(sym-collidine)iodine(I) tetrafluoroborate (59) in dimethyl sulfoxide is a potential reagent for the direct conversion of alkenes to a-iodo carbonyl compounds (Scheme 6). The oxidation involves the... 

By the reaction of iodine and small amounts of liquid ammonia at -75° a black brown solid is formed. A tensimetric deammonation shows that this solid is an addition compound of iodine and ammonia with 2 moles of ammonia per mole of iodine. Further deammonation effects formation of a compound Ij.NH finally, I remains. Ammonolysis of iodine takes place only to a small extent. These brown addition compounds of iodine correspond to the well known brown addition compounds of iodine and ether, alcohol, pyridine or liquid hydrogen sulfide respectively and are looked upon as charge-transfer complexes with iodine as electron acceptor and the solvents as electron donors. This view was proved by the measurement of the charge transfer band of iodine-ammonia in heptane at 229 m i (2). 

Aloisi, G., Cauzzo, G. and Mazzucato, U. (1967) Charge transfer complexes between iodine and aromatic aza compounds. III. Pyridine and derivatives. Trans. Faraday Soc., 1858-1862. Masaguer, J.R., Sousa-Alonso, A., Garcia-Vazquez, J. A. and Blanco, A. (1977) Charge-transfer molecular complexes. Interaction of iodine with dimethyl pyridines. Afinidad, 34,186-190. Bhaskar, K.R. and Singh, S. (1967) Spectroscopic studies of n-donor-n-acceptor systems pyridines. Spectrochim. Acta, Part A, 33A, 1155-1159. 

Abstract This presentation is a brief review on the resnlts of our work on iodine interaction with thioamides, selenoamides and amides. The thioamides, benzothia-zole-2-thione (BZT) (1), 6-n-propyl-2-thiouracil (PTU) (2), 5-chloro-2-mercap-tobenzothiazole (CMBZT) (3), N-methyl-benzothiazole-2-thione (NMBZT) (4), benzimidazole-2-thione (BZIM) (5), thiazolidine-2-thione (TZD) (6), 2-mercapto-pyridine (PYSH) (7), 2-mercapto-nicotinic acid (MNA) (8), 2-mercapto-benzoic acid (MBA) (9) and 2-mercapto-pyrimidine (PMT) (10) react with producing three type of complexes of formulae [(HL)IJ(l2) (HL= thioamide and n= 0, 1), [(HL) [I3 ] and [(HL-L)]+[l3 ]. The interaction of seleno-amides, derived from, 6-n-propyl-2-thiouracil (RSelJ) (R= Me- (11), Et- (12), n-Pr- (13) and i-Pr- (14)) with I, have also been studied and produced the complexes [(RSeU)IJ of spoke structure. These complexes are stable in non-polar solvents, but they decompose in polar solvents, producing dimeric diselenide compounds or undertake deselenation. 

A very large number of complexes of pyridines and quinolines with all the halogens and interhalogen compounds are known, and as they have been enumerated elsewhere (74HQ14-S2)407,77HC(32-1)319) just a few examples are illustrated (Scheme 14). Treatment of pyridine with chlorine or bromine in the presence of aluminum chloride yields 4-pyridylpyridinium salts (equation 29), but rather curiously the action of iodine chloride on pyridinium hydrochloride at 250 °C produces the 2-isomer (51 equation 30). 

The chemistry of the JV-oxides of oxazole has not been explored as thoroughly as that of the pyridine analogues. Both types of compounds are reversibly protonated to give iV-hydroxy cations, form complexes with iodine and with tetracyanoethylene, and both are deoxygenated by triphenylphosphine and other tervalent phosphorus compounds. 

Reaction of the arylamine 62 with the complex salt 52 in acetonitrile at room temperature afforded complex 64 in 87% yield (Scheme 17) [125]. Subsequent oxidative cyclization, aromatization and demetalation using iodine in pyridine provided carbazole 65 in 71% yield. Heating of compound 65 in chlorobenzene in the presence of the acidic cation exchange resin amberlyst 15 led to ring closure with formation of the furo[3,2-a]carbazole 66. Oxidation of the methyl group at C-3 to a formyl group using 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ)... 

In contrast, however, it must be considered that the rate of the reaction involving iodine bound in the complex by pyridine is only halved, and is still very high (at 20 °C in cyclohexane, fc = 2.9 x 10 1 mole" s" ). This points to the possibility of another reaction between the Ps and iodine, proceeding in parallel with the previous one. This other reaction may consist of dissociation of the iodine molecule and formation of the compound PsI as an intermediate. This reaction path is not influenced substantially by the bond formed between the pyridine and iodine. 

Bis(trifluoromethyl)platinum complexes may conveniently be prepared by the reaction of dimethyl(cyclo-octa-l,5-diene)platinum with trifluoro-iodomethane in methylene chloride, followed by displacement of the cydo-octadiene with the required ligand L (L = AsMcs, PMeaPh, pyridine, RNC, etc.) Oxidative addition of iodine thence gives the platinum(iv) compounds ... 

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