Chakraborty Indranil, Panda Bikash Kumar, Gangopadhyay Jaydip, Chakravorty Animesh
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700 032, India.
Inorg Chem. 2005 Feb 21;44(4):1054-60. doi: 10.1021/ic0486116.
The concerned azooximes (L1OH, 1) are of type p-X-C6H4C(N2Ph)(NOH) (X = H, Me, Cl). The reaction of [Re(MeCN)Cl3(PPh3)2] with [Ag(L1OH)(L1O)] in cold dichloromethane-acetonitrile solvent has furnished the green colored ionized azoimine complex ReV(O)Cl(PPh3)2(L1), 2. In effect L1O- has undergone oxidative addition, the oxygen atom being transferred to the metal site. Upon treatment of [ReV(NPh)Cl3(PPh3)2] with L1OH in solution, the neutral azoimine complex [ReV(NPh)Cl3(L1H)], 3, resulted due to the spontaneous transfer of the oxime oxygen atom to a PPh3 ligand, which is eliminated as OPPh3. In contrast, the oxime of 2-acetylpyridine (L2OH, 4) did not undergo oxygen atom transfer and simply afforded the imine-oxime complex [ReV(NC6H4Y)Cl2(PPh3)(L2O)], 5, upon reacting with [ReV(NC6H4Y)Cl3(PPh3)2] (Y = H, Me, Cl). The spectral and electrochemical properties of 2, 3, and 5 and the structures of three representative compounds are reported. In the cation of 2 (X = H) the two PPh3 ligands lie trans to each other and the equatorial plane is defined by the five-membered azoimine chelate ring and the oxo and chloro ligands. The oxo ligand which forms a model triple bond (Re-O length 1.616(6) A) lies cis to the imine-N atom. In 3 (X = Cl) the ReCl3 fragment has meridional geometry and the imido nitrogen lies trans to the imine nitrogen of the planar azoimine chelate ring. In 5 x H2O (Y = Me), the Cl, oximato-N, and P atoms define an equatorial plane and the pyridine-N lies trans to the imido-N. The water of crystallization is hydrogen bonded to the oximato oxygen atom (O...O, 2.829(5) A). Reaction models in which chelation of the azooxime precedes oxygen atom transfer are proposed on the basis of oxophilicity of trivalent rhenium, Lewis acid activity of pentavalent rhenium, electron withdrawal by the azo group, and observed relative disposition of ligands in products.
所涉及的偶氮肟（L1OH，1）为p-X-C6H4C（N2Ph）（NOH）类型（X = H、Me、Cl）。[Re（MeCN）Cl3（PPh3）2]与[Ag（L1OH）（L1O）]在冷二氯甲烷 - 乙腈溶剂中反应，得到了绿色的离子化偶氮亚胺配合物ReV（O）Cl（PPh3）2（L1），即2。实际上，L1O-发生了氧化加成，氧原子转移到了金属位点。在溶液中用L1OH处理[ReV（NPh）Cl3（PPh3）2]时，由于肟氧原子自发转移到一个PPh3配体上并以OPPh3形式消除，得到了中性偶氮亚胺配合物[ReV（NPh）Cl3（L1H）]，即3。相比之下，2-乙酰吡啶的肟（L2OH，4）未发生氧原子转移，与[ReV（NC6H4Y）Cl3（PPh3）2]（Y = H、Me、Cl）反应时仅得到亚胺 - 肟配合物[ReV（NC6H4Y）Cl2（PPh3）（L2O）]，即5。报道了2、3和5的光谱和电化学性质以及三种代表性化合物的结构。在2（X = H）的阳离子中，两个PPh3配体彼此反位，赤道平面由五元偶氮亚胺螯合环以及氧代和氯配体确定。形成模型三键（Re - O键长1.616(6) Å）的氧代配体与亚胺 - N原子顺位。在3（X = Cl）中，ReCl³片段具有经向几何结构，亚氨基氮与平面偶氮亚胺螯合环的亚胺氮反位。在5·H₂O（Y = Me）中，Cl、肟基 - N和P原子确定一个赤道平面，吡啶 - N与亚氨基 - N反位。结晶水通过氢键与肟基氧原子相连（O...O，2.829(5) Å）。基于三价铼的亲氧性、五价铼的路易斯酸活性、偶氮基团的吸电子作用以及产物中观察到的配体相对排布，提出了偶氮肟螯合先于氧原子转移之前的反应模型。
