Osazone Anion Radical Complex of Rhodium(III)

One electron paramagnetic parent osazone complex of rhodium of type trans-Rh(LNHPhH2)(PPh3)2Cl2 (1), defined as an osazone anion radical complex of rhodium(III), trans-RhIII(LNHPhH2•−)(PPh3)2Cl2, 1(t-RhL•), with a minor contribution (∼2%) of rhodium(II) electromer, trans-RhII(LNHPhH2)(PPh3)2Cl2, 1(t-Rh•L), and their nonradical congener, trans-[RhIII(LNHPhH2)(PPh3)2Cl2]I3 ([t-1]+I3−), have been isolated and are substantiated by spectra, bond parameters, and DFT calculations on equivalent soft complexes [Rh(LNHPhH2)(PMe3)2Cl2] (3) and [Rh(LNHPhH2)(PMe3)2Cl2]+ (3+). 1 is not stable in solution and decomposes to [t-1]+ and a new rhodium(I) osazone complex, [RhI(LNHPhH2)(PPh3)Cl] (2). 1 absorbs strongly at 351 nm due to MLCT and LLCT, while [t-1]+ and 2 absorb moderately in the range of 300−450 nm, respectively, due to LMCT and MLCT elucidated by TD-DFT calculations on 3(t-RhL•), [t-3]+, and RhI(LNHPhH2)(PMe3)Cl (4). EPR spectra of solids at 295 and 77 K, and dichloromethane−toluene frozen glass at 77 K of 1 are similar with g = 1.991, while g = 2.002 for the solid at 25 K. The EPR signal of 1 in dichloromethane solution is weaker (g = 1.992). In cyclic voltammetry, 1 displays two irreversible one electron transfer waves at +0.13 and −1.22 V, with respect to Fc+/Fc coupling, due to oxidation of 1(t-RhL•) to [t-1]+ at the anode and reduction of rhodium(III) to rhodium(II), i.e., [t-1]+ to electromeric 1(t-Rh•L) at the cathode.我们成功分离得到一类反式构型的铑基单电子顺磁性母核脎（osazone）配合物trans-Rh(LNHPhH2)(PPh3)2Cl2（记为1），其被定义为铑(III)的脎阴离子自由基配合物trans-RhIII(LNHPhH2•−)(PPh3)2Cl2，即1(t-RhL•)；该体系同时存在约2%占比的铑(II)电子异构体trans-RhII(LNHPhH2)(PPh3)2Cl2，即1(t-Rh•L)。此外，我们还分离得到了其非自由基同构型配合物trans-[RhIII(LNHPhH2)(PPh3)2Cl2]I3（记为[t-1]+I3−）。上述配合物均通过光谱表征、键参数分析，以及对等效软配位配合物[Rh(LNHPhH2)(PMe3)2Cl2]（3）和[Rh(LNHPhH2)(PMe3)2Cl2]+（3+）的密度泛函理论（DFT）计算得到了验证。 配合物1在溶液中不稳定，会分解为[t-1]+与一种新型铑(I)脎配合物[RhI(LNHPhH2)(PPh3)Cl]（记为2）。 1在351 nm处存在强吸收峰，源于金属到配体电荷转移（Metal-to-Ligand Charge Transfer, MLCT）与配体到配体电荷转移（Ligand-to-Ligand Charge Transfer, LLCT）；而[t-1]+与2分别在300−450 nm范围内呈现中等强度吸收，对应配体到金属电荷转移（Ligand-to-Metal Charge Transfer, LMCT）与金属到配体电荷转移（MLCT），该结论通过对1(t-RhL•)、[t-3]+以及RhI(LNHPhH2)(PMe3)Cl（4）的含时密度泛函理论（Time-Dependent Density Functional Theory, TD-DFT）计算得以阐明。 在295 K与77 K下的固体样品、77 K下的二氯甲烷-甲苯冷冻玻璃态样品的电子顺磁共振（Electron Paramagnetic Resonance, EPR）光谱均显示g因子为1.991；而25 K下的固体样品g因子为2.002。1在二氯甲烷溶液中的EPR信号较弱，其g因子为1.992。 循环伏安测试中，相对于二茂铁/二茂铁正离子（Fc+/Fc）参比氧化还原对，1在+0.13 V与−1.22 V处出现两个不可逆的单电子转移波：阳极侧对应1(t-RhL•)被氧化为[t-1]+，阴极侧则对应铑(III)被还原为铑(II)，即[t-1]+转化为电子异构体1(t-Rh•L)。