The dinuclear complex [Mo(TpMe,Me)(NO)Cl}2(µ-L2)] 2 [L2 is the new bridging ligand 2,7-bis2-(4-pyridyl)ethen-1-yl}fluorenone] contains two redox-active molybdenum(I) centres linked by a bridging ligand which is itself redox-active by virtue of the fluorenone spacer unit. The complex undergoes four one-electron reductions of which two are metal-centred Mo(0)/Mo(I) couples and two are reductions of the fluorenone unit. Also studied were the mononuclear analogue [Mo(TpMe,Me)(NO)Cl(L1)] [L1 is 2-bromo-7-2-(4-pyridyl)ethen-1-yl}fluorenone], and the dinuclear complex [Mo(TpMe,Me)(NO)Cl}2(µ-L3)] 3 [L3 is the bridging ligand 2,7-bis2-(4-pyridyl)ethen-1-yl}fluorene] which lacks the ligand-centred redox activity. A combination of EPR and UV/VIS/NIR spectroelectrochemical techniques was used and showed how the separate metal-centred and ligand-centred reduction processes lead to quite distinct and characteristic spectroscopic signatures, such that it was possible to assign the sequence of reduction sites as ligandâmetalâmetalâligand. The initial reduction of the bridging ligand in 2 results in a much larger separation between the two Mo(0)/Mo(I) couples (240 mV) than occurs in complexes where the bridging ligand is not redox-active.
二核复合物 [Mo(TpMe,Me)(NO)Cl}2(µ-
L2)] 2 [
L2 是新型桥联
配体 2,7-bis2-(4-pyridyl)ethen-1-yl}fluorenone] 含有两个具有氧化还原活性的
钼(I)中心,这两个中心通过一个本身也具氧化还原活性的桥联
配体连接,该
配体的氧化还原活性源于其含有的
氟酮间隔单位。该复合物经历了四次单电子还原,其中两次为
金属中心的 Mo(0)/Mo(I) 对,另外两次为
氟酮单位的还原。此外,还研究了单核类似物 [Mo(TpMe,Me)(NO)Cl(L1)] [L1 是 2-bromo-7-2-(4-pyridyl)ethen-1-yl}fluorenone],以及二核复合物 [Mo(TpMe,Me)(NO)Cl}2(µ-L3)] 3 [L3 是缺乏
配体中心氧化还原活性的桥联
配体 2,7-bis2-(4-pyridyl)ethen-1-yl}fluorene]。结合 EPR 和 UV/VIS/NIR 光谱电
化学技术的研究显示,
金属中心和
配体中心的还原过程产生了截然不同且具有特征的光谱特征,因此能够将还原位点的顺序指定为
配体-
金属-
金属-
配体。在 2 中,桥联
配体的初始还原导致两个 Mo(0)/Mo(I) 对之间的分离显著增大(240 mV),而在桥联
配体不具氧化还原活性的复合物中则不会出现这种情况。