Departamento de Química Orgánica e Inorgánica, Facultad de Química, Universidad de Oviedo, 33006, Oviedo, Spain.
Dalton Trans. 2009 Sep 21(35):6999-7007. doi: 10.1039/b906450h. Epub 2009 Jul 3.
Tautomerization of coordinated azoles to their corresponding N-heterocyclic carbenes (NHCs) has been carried out by reaction of complexes fac-Mn(L)(CO)(3)(dppe) (L = N-phenylimidazole) and fac-Mn(L)(CO)(3)(bipy) (L = N-methylbenzimidazole, benzoxazole, benzothiazole) with KO(t)Bu and subsequent protonation of the azolyl intermediates with NH(4)PF(6). Several NHC-manganese(i) complexes bearing an N-H residue of general formula fac-Mn(NHC)(CO)(3)(dppe) and fac-Mn(NHC)(CO)(3)(bipy) have been tested as carbene transfer agents to the gold fragments Au(L) (L = PPh(3), CNPh, CNXylyl), allowing isolation or spectroscopic detection of various Mn(i)/Au(i) heterometallic intermediates containing azolyl bridging ligands, which liberate the gold(i) carbene complexes Au(NHC)(L) by means of acid hydrolysis. By contrast, when using the silver(i) fragment Ag(PPh(3)) as carbene acceptor no transmetallation process occurred but instead inverse tautomerization of the NHC to the corresponding imidazole ligand was observed.
通过反应配合物 fac-Mn(L)(CO)(3)(dppe)（L = N-苯基咪唑）和 fac-Mn(L)(CO)(3)(bipy)（L = N-甲基苯并咪唑、苯并恶唑、苯并噻唑）与 KO(t)Bu 进行配位唑的互变异构化，生成相应的 N-杂环卡宾（NHC），随后用 NH(4)PF(6)对唑基中间体进行质子化。我们测试了几种含有 N-H 残基的 NHC-锰(i)配合物，其通式为 fac-Mn(NHC)(CO)(3)(dppe) 和 fac-Mn(NHC)(CO)(3)(bipy)，作为碳烯转移试剂，用于金片段 Au(L)（L = PPh(3)、CNPh、CNXylyl），允许分离或光谱检测含有唑桥配体的各种 Mn(i)/Au(i)杂金属中间体，通过酸水解释放出金(i)碳烯配合物 Au(NHC)(L)。相比之下，当使用银(i)片段 Ag(PPh(3)) 作为碳烯受体时，没有发生转金属过程，而是观察到 NHC 向相应的咪唑配体的逆互变异构化。
