Kurtikyan T S, Hayrapetyan V A, Mehrabyan M M, Ford P C
Molecule Structure Research Centre (MSRC) of the Scientific and Technological Centre of Organic and Pharmaceutical Chemistry NAS , 375014, Yerevan, Armenia.
Inorg Chem. 2014 Nov 17;53(22):11948-59. doi: 10.1021/ic5014329. Epub 2014 Nov 4.
Reaction of small increments of NO2 gas with sublimed amorphous layers of Mn(II)(TPP) (TPP = meso-tetra-phenylporphyrinato dianion) in a vacuum cryostat leads to formation of the 5-coordinate monodentate nitrato complex Mn(III)(TPP)(η(1)-ONO2) (II). This transformation proceeds through the two distinct steps with initial formation of the five coordinate O-nitrito complex Mn(III)(TPP)(η(1)-ONO) (I) as demonstrated by the electronic absorption spectra and by FTIR spectra using differently labeled nitrogen dioxide. A plausible mechanism for the second stage of reaction is offered based on the spectral changes observed upon subsequent interaction of (15)NO2 and NO2 with the layered Mn(TPP). Low-temperature interaction of I and II with the vapors of various ligands L (L = O-, S-, and N-donors) leads to formation of the 6-coordinate O-nitrito Mn(III)(TPP)(L)(η(1)-ONO) and monodentate nitrato Mn(III)(TPP)(L)(η(1)-ONO2) complexes, respectively. Formation of the 6-coordinate O-nitrito complex is accompanied by the shifts of the ν(N═O) band to lower frequency and of the ν(N-O) band to higher frequency. The frequency difference between these bands Δν = ν(N═O) - ν(N-O) is a function of L and is smaller for the stronger bases. Reaction of excess NH3 with I leads to formation of Mn(TPP)(NH3)(η(1)-ONO) and of the cation Mn(TPP)(NH3)2 plus ionic nitrite. The nitrito complexes are relatively unstable, but several of the nitrato species can be observed in the solid state at room temperature. For example, the tetrahydrofuran complex Mn(TPP)(THF)(η(1)-ONO2) is stable in the presence of THF vapors (∼5 mm), but it loses this ligand upon high vacuum pumping at RT. When L = dimethylsulfide (DMS), the nitrato complex is stable only to ∼-30 °C. Reactions of II with the N-donor ligands NH3, pyridine, or 1-methylimidazole are more complex. With these ligands, the nitrato complexes Mn(III)(TPP)(L)(η(1)-ONO2) and the cationic complexes Mn(TPP)(L)2 coexist in the layer at room temperature, the latter formed as a result of NO3(-) displacement when L is in excess.
在真空低温恒温器中，少量二氧化氮气体与升华的无定形Mn(II)(TPP)（TPP = 中-四苯基卟啉二价阴离子）层反应，生成五配位单齿硝酸根配合物Mn(III)(TPP)(η(1)-ONO2)（II）。这种转变通过两个不同的步骤进行，最初形成五配位亚硝酸根配合物Mn(III)(TPP)(η(1)-ONO)（I），这已通过电子吸收光谱以及使用不同标记的二氧化氮的傅里叶变换红外光谱得到证明。基于(15)NO2和NO2与层状Mn(TPP)后续相互作用时观察到的光谱变化，提出了反应第二阶段的合理机制。I和II与各种配体L（L = O-、S-和N-供体）的蒸气在低温下相互作用，分别生成六配位亚硝酸根Mn(III)(TPP)(L)(η(1)-ONO)和单齿硝酸根Mn(III)(TPP)(L)(η(1)-ONO2)配合物。六配位亚硝酸根配合物的形成伴随着ν(N═O)带向低频移动以及ν(N - O)带向高频移动。这些带之间的频率差Δν = ν(N═O) - ν(N - O)是L的函数，对于较强的碱来说较小。过量NH3与I反应生成Mn(TPP)(NH3)(η(1)-ONO)以及阳离子Mn(TPP)(NH3)2和离子型亚硝酸盐。亚硝酸根配合物相对不稳定，但几种硝酸根物种在室温下的固态中可以观察到。例如，四氢呋喃配合物Mn(TPP)(THF)(η(1)-ONO2)在四氢呋喃蒸气（约5毫米汞柱）存在下是稳定的，但在室温下高真空泵抽时会失去该配体。当L = 二甲基硫醚（DMS）时，硝酸根配合物仅在约 - 30°C下稳定。II与N-供体配体NH3、吡啶或1-甲基咪唑的反应更为复杂。对于这些配体，硝酸根配合物Mn(III)(TPP)(L)(η(1)-ONO2)和阳离子配合物Mn(TPP)(L)2在室温下在层中共存，后者是当L过量时由于NO3(-)被取代而形成的。
