Electronic Structures of Ruthenium and Osmium Complexes of 9,10-Phenanthrenequinone
详细信息 查看全文
- 作者：Manas Kumar Biswas ; Sarat Chandra Patra ; Amarendra Nath Maity ; Shyue-Chu Ke ; Nirmal Das Adhikary ; Prasanta Ghosh
- 刊名：Inorganic Chemistry
- 出版年：2012
- 出版时间：June 18, 2012
- 年：2012
- 卷：51
- 期：12
- 页码：6687-6699
- 全文大小：526K
- 年卷期：v.51,no.12(June 18, 2012)
- ISSN：1520-510X
文摘
The reaction of 9,10-phenanthrenequinone (PQ) with [MII(H)(CO)(X)(PPh3)3] in boiling toluene leads to the homolytic cleavage of the MII鈥揌 bond, affording the paramagnetic trans-[M(PQ)(PPh3)2(CO)X] (M = Ru, X = Cl, 1; M = Os, X = Br, 3) and cis-[M(PQ)(PPh3)2(CO)X] (M = Ru, X = Cl, 2; M = Os, X = Br, 4) complexes. Single-crystal X-ray structure determinations of 1, 2路toluene, and 4路CH2Cl2, EPR spectra, and density functional theory (DFT) calculations have substantiated that 1鈥?b>4 are 9,10-phenanthrenesemiquinone radical (PQ鈥⑩€?/sup>) complexes of ruthenium(II) and osmium(II) and are defined as trans-[RuII(PQ鈥⑩€?/sup>)(PPh3)2(CO)Cl] (1), cis-[RuII(PQ鈥⑩€?/sup>)(PPh3)2(CO)Cl] (2), trans-[OsII(PQ鈥⑩€?/sup>)(PPh3)2(CO) Br] (3), and cis-[OsII(PQ鈥⑩€?/sup>)(PPh3)2(CO)Br] (4). Two comparatively longer C鈥揙 [average lengths: 1, 1.291(3) 脜; 2路toluene, 1.281(5) 脜; 4路CH2Cl2, 1.300(8) 脜] and shorter C鈥揅 lengths [1, 1.418(5) 脜; 2路toluene, 1.439(6) 脜; 4路CH2Cl2, 1.434(9) 脜] of the OO chelates are consistent with the presence of a reduced PQ鈥⑩€?/sup> ligand in 1鈥?b>4. A minor contribution of the alternate resonance form, trans- or cis-[MI(PQ)(PPh3)2(CO)X], of 1鈥?b>4 has been predicted by the anisotropic X- and Q-band electron paramagnetic resonance spectra of the frozen glasses of the complexes at 25 K and unrestricted DFT calculations on 1, trans-[Ru(PQ)(PMe3)2(CO)Cl] (5), cis-[Ru(PQ)(PMe3)2(CO)Cl] (6), and cis-[Os(PQ)(PMe3)2(CO)Br] (7). However, no thermodynamic equilibria between [MII(PQ鈥⑩€?/sup>)(PPh3)2(CO)X] and [MI(PQ)(PPh3)2(CO)X] tautomers have been detected. 1鈥?b>4 undergo one-electron oxidation at 鈭?.06, 鈭?.05, 0.03, and 鈭?.03 V versus a ferrocenium/ferrocene, Fc+/Fc, couple because of the formation of PQ complexes as trans-[RuII(PQ)(PPh3)2(CO)Cl]+ (1+), cis-[RuII(PQ)(PPh3)2(CO)Cl]+ (2+), trans-[OsII(PQ)(PPh3)2(CO)Br]+ (3+), and cis-[OsII(PQ)(PPh3)2(CO)Br]+ (4+). The trans isomers 1 and 3 also undergo one-electron reduction at 鈭?.11 and 鈭?.96 V, forming PQ2鈥?/sup> complexes trans-[RuII(PQ2鈥?/sup>)(PPh3)2(CO)Cl]鈭?/sup> (1鈥?/b>) and trans-[OsII(PQ2鈥?/sup>)(PPh3)2(CO)Br]鈭?/sup> (3鈥?/b>). Oxidation of 1 by I2 affords diamagnetic 1+I3鈥?/sup> in low yields. Bond parameters of 1+I3鈥?/sup> [C鈥揙, 1.256(3) and 1.258(3) 脜; C鈥揅, 1.482(3) 脜] are consistent with ligand oxidation, yielding a coordinated PQ ligand. Origins of UV鈥搗is/near-IR absorption features of 1鈥?b>4 and the electrogenerated species have been investigated by spectroelectrochemical measurements and time-dependent DFT calculations on 5, 6, 5+, and 5鈥?/b>.