Dioxygenation of Sterically Hindered (Ethene)Rh~I and -Ir~I Complexes to (Peroxo)Rh~III and (Ethene)(peroxo)Ir~III (Complexes

摘要

New cationic, five-coordinate bis(ethene)iridium(i) complexes [(k~3-Me_3-tpa)Ir~I(ethene)_2]~+ (12~+) and [(k~3-Me-dpa-Me)Ir~I(ethene)_2]~+ (13~+) have been prepared {Me_3-tpa= N,N,N-tris[(6-methyl-2-pyridyl)methyl]amine, Me_2-dpa-Me=N-methyl-N,N-bis[(6-methyl-2-pyridyl)methyl]amine}. Complexes 12~+ and 13~+ lose one ethene fragment in solution, yielding the five-coordinate mono(ethene) complex [(k~4-Me_3-tpa)Ir~I(ethene)]~+ (14) and the four-coordinate mono-(ethene) complex [(k~3-Me_2-dpa-Me)Ir~I(ethene)]~+ (15~+), respectively. [(k~4-Me_3-tpa)Rh~I(ethene)]~+ (11~+), the rhodium analogure of 14~+, was also prepared. Whereas rhodium complex 11~+ is stable in acetonitrile at room temperature, the iridium anagloue 14~+ converts to the cyclometallated (acetonitrile)(hydrido) complex 16~+ within 72 h by dissociation of the unique 6-methylpyridyl fragment and oxidative addition of the 6-methylpyridyl C~3-H bond. The four-coordinate mono(-ethene) complex 15~+ is even less stable in solution; it converts to a mixture of compounds within 18 h. Reaction of the mono(ethene)Rh~I complex 11~+ with O_2 yields the peroxo complex 17~+ by ethene displacement. In contrast, the mono(ethene)Ir~I complexes 14~+ and 15~+ bind O_2 without the loss of ethene, leading to unprecedented (ethene)(peroxo)Ir~III complexes 18~+ and 19~+. At room temperature, peroxo complex 17~+ does not react with ethene and, quite remarkably, C-O bond formation does not occur in the (ethene)(peroxo) complexes 18~+ and 19~+.