Robert F. Pasternack, Bruce S. Gillies, Julia P. Stromsted
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引用次数: 8
摘要
四akis-(4- n -甲基吡啶基)卟啉钴(III) (CoIIITMpyP)与叠氮化物和1,1,3,3-四甲基-2-硫脲(TMTU)在25°和0.5 m离子强度下的取代反应作为pH的函数进行了研究。提出的硫氰酸盐[1]和吡啶[2]的机制途径也适用于这些配体,只要考虑到两种攻击形式的叠氮化物N3 -和HN3。TMTU轴向取代基对配体进一步取代速率的影响与SCN -差不多,比叠氮化物的影响大得多。在与Ru(NH3)62+ -的电子转移反应中,结合的SCN -和结合的TMTU之间也表现出类似的行为。尽管两种含硫配体相对于双水络合物都提高了速率,叠氮化物络合物的还原速度比双水络合物慢一个量级。
Substitution reactions of a water-soluble metalloporphyrin with azide and 1,1,3,3-tetramethyl-2-thiourea
The substitution reactions of tetrakis-(4-N-methylpyridyl)porphinecobalt (III) (CoIIITMpyP) with azide and with 1,1,3,3-tetramethyl-2-thiourea (TMTU) have been studied as a function of pH at 25° and an ionic strength of 0.5 M. The mechanistic pathway proposed for thiocyanate [1] and pyridine [2] is applicable to these ligands as well once allowance is made for two attacking forms of azide, N3— and HN3. A TMTU axial substituent has about the same influence on the rate of further ligand substitution as does SCN— and a much larger influence than does azide. Similar behavior between bound SCN— and bound TMTU is also shown in electron-transfer reactions with Ru(NH3)62+ - Whereas both sulfur-containing ligands enhance the rate relative to the diaquo complex, the azide complex undergoes reduction an order of magnitude more slowly than does the diaquo complex.