Activation of Nitrogen Brønsted Acids: Synthesis and Reactivity of a New Class of Nitrogen Acid Complexes

The nitrogen acids RC­(O)­NHNO2, N-nitroamide, R = CH3 (1), C2H5 (2) and N-nitrocarbamate, R′OC­(O)­NHNO2, R′ = CH3 (3), C2H5 (4) are a class of primary N-nitrocarboxamide
compounds that oxidatively add to trans-Ir(I)(Cl)­(N2)­(PPh3)2 to give six-coordinate
Ir(III)(η2-(NO2)-nitrogen acid)­(H)­(Cl)­(PPh3)2 complexes 5–8. Unexpected fluxional behavior of the complexes in solution is observed
by 1H NMR spectroscopy. Reaction intermediates of the oxidative
addition reactions were also observed and monitored using 31P and 1H NMR and solution IR spectroscopies. Complex 5 reacts with methyl triflate in CH3CN to generate
bis­(acetonitrile) complex (9) from a net loss of the
nitrogen acid anion. P­(CH3)2Ph reacts with 5 to give phosphine-substituted and P­(CH3)2Ph addition isomers (10). Reactivity studies
of 5 with CO gave metastable CO adduct isomer 11, which loses CO on prolonged standing in solution.

一类伯N-硝基羧酰胺类化合物包含两类氮酸衍生物：其一为通式RC(O)NHNO₂的N-硝基酰胺（R=CH₃(1)、C₂H₅(2)），其二为通式R'OC(O)NHNO₂的N-硝基氨基甲酸酯（R'=CH₃(3)、C₂H₅(4)）。该类化合物可与反式-二氮·氯化·二(三苯基膦)合铱(I)[trans-Ir(I)(Cl)(N₂)(PPh₃)₂]发生氧化加成反应，生成六配位的Ir(III)(η²-(NO₂)-氮酸)(H)(Cl)(PPh₃)₂配合物5~8。通过氢核磁共振（¹H NMR）波谱法可观测到该系列配合物在溶液中存在反常的流变行为。本研究还通过磷核磁共振（³¹P NMR）、氢核磁共振波谱法与溶液相红外光谱（IR）法，对氧化加成反应的中间体进行了观测与监测。配合物5与三氟甲磺酸甲酯在乙腈(CH₃CN)中反应，经净脱除氮酸阴离子后生成双(乙腈)合铱配合物(9)。二甲基苯基膦[P(CH₃)₂Ph]与配合物5反应，得到膦取代且二甲基苯基膦加成的异构体(10)。针对配合物5与一氧化碳(CO)的反应性研究显示，二者可生成亚稳态的CO加合物异构体11，该加合物在溶液中静置较长时间后会脱除CO。