Pal Raja, Cherry Brian R, Flores Marco, Groy Thomas L, Trovitch Ryan J
School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, USA.
Dalton Trans. 2016 Jun 14;45(24):10024-33. doi: 10.1039/c6dt00301j.
Analysis of previously reported [((Ph2PPr)PDI)MoI][I] by cyclic voltammetry revealed a reversible wave at -1.20 V vs. Fc(+/0), corresponding to the Mo(ii)/Mo(i) redox couple. Reduction of [((Ph2PPr)PDI)MoI][I] using stoichiometric K/naphthalene resulted in ligand deprotonation rather than reduction to yield a Mo(ii) monoiodide complex featuring a Mo-C bond to the α-position of one imine substituent, (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI. Successful isolation of the inner-sphere Mo(i) monoiodide complex, ((Ph2PPr)PDI)MoI, was achieved via reduction of [((Ph2PPr)PDI)MoI][I] with equimolar Na/naphthalene. This complex was found to have a near octahedral coordination geometry by single crystal X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopy revealed an unpaired Mo-based electron which is highly delocalized onto the PDI chelate core. Attempts to prepare a Mo(i) monohydride complex upon adding NaEt3BH to ((Ph2PPr)PDI)MoI resulted in disproportionation to yield an equimolar quantity of (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoH and newly identified ((Ph2PPr)PDI)MoH2. Independent preparation of ((Ph2PPr)PDI)MoH2 was achieved by adding 2 equiv. NaEt3BH to [((Ph2PPr)PDI)MoI][I] and a minimum hydride resonance T1 of 176 ms suggests that the Mo-bound H atoms are best described as classical hydrides. Interestingly, ((Ph2PPr)PDI)MoH2 can be converted to (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI upon iodomethane addition, while ((Ph2PPr)PDI)MoH2 is prepared from (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI in the presence of excess NaEt3BH. Similarly, (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI can be converted to (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoH with 1 equiv. of NaEt3BH, while the opposite transformation occurs following iodomethane addition to (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoH. Facile interconversion between [((Ph2PPr)PDI)MoI][I], (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI, (κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoH, and ((Ph2PPr)PDI)MoH2 is expected to guide future reactivity studies on this unique set of compounds.
通过循环伏安法对先前报道的[((Ph2PPr)PDI)MoI][I]进行分析，发现在相对于Fc(+/0)为 -1.20 V处有一个可逆波，对应于Mo(ii)/Mo(i)氧化还原对。使用化学计量的K/萘还原[((Ph2PPr)PDI)MoI][I]导致配体去质子化，而非还原生成一种Mo(ii)单碘配合物，该配合物在一个亚胺取代基的α位具有Mo-C键，即(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI。通过用等摩尔的Na/萘还原[((Ph2PPr)PDI)MoI][I]成功分离出内球型Mo(i)单碘配合物((Ph2PPr)PDI)MoI。通过单晶X射线衍射发现该配合物具有近乎八面体的配位几何结构，电子顺磁共振（EPR）光谱显示有一个未成对的基于Mo的电子，该电子高度离域到PDI螯合核上。向((Ph2PPr)PDI)MoI中加入NaEt3BH试图制备Mo(i)单氢化物配合物，结果发生歧化反应，生成等摩尔量的(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoH和新鉴定出的((Ph2PPr)PDI)MoH2。通过向[((Ph2PPr)PDI)MoI][I]中加入2当量的NaEt3BH独立制备出((Ph2PPr)PDI)MoH2，并且最小氢化物共振T1为176 ms表明与Mo相连的H原子最好描述为经典氢化物。有趣的是，加入碘甲烷后((Ph2PPr)PDI)MoH2可转化为(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI，而((Ph2PPr)PDI)MoH2是在过量NaEt3BH存在下由(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI制备的。同样，(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI用1当量的NaEt3BH可转化为(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoH，而向(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoH中加入碘甲烷后会发生相反的转化。[((Ph2PPr)PDI)MoI][I]、(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoI、(κ(6)-P,N,N,N,C,P-(Ph2PPr)PDI)MoH和((Ph2PPr)PDI)MoH2之间的 facile 相互转化有望指导对这组独特化合物的未来反应性研究。
