A New Spin on Cyclooctatetraene (COT) Redox Activity: Low-Spin Iron(1) Complexes That Exhibit Antiferromagnetic Coupling to a Singly Reduced eta(4)-COT Ligand

作者：Mukhopadhyay Tufan K; Flores Marco; Feller Russell K; Scott Brian L; Taylor R Dean; Paz Pasternak Moshe; Henson Neil J; Rein Francisca N; Smythe Nathan C^*; Trovitch Ryan J; Gordon John C

来源：Organometallics, 2014, 33(24): 7101-7112.

DOI：10.1021/om500909h

Formally zerovalent (kappa(3)-phosphine)Fe(eta(4)-COT) complexes supported by either Triphos (PhP(CH2CH2PPh2)(2)) or Triphos* (H3CC(CH2PPh2)(3)) have been prepared following chelate addition to (COT)(2)Fe (COT = 1,3,5,7-cyclooctatetraene) and by reduction of the respective dibromide complexes in the presence of excess COT. The solid-state structure of each complex was determined by single-crystal X-ray diffraction, and close inspection of the metrical parameters revealed significant COT ligand reduction, independent of the coordination geometry about iron. While the neutral and dianionic forms of the redox-active COT ligand have historically received a great deal of attention, a dearth of information regarding the often-evoked radical monoanion form of this ligand prompted the full electronic structure investigation of these complexes using a range of techniques. Comparison of the Mossbauer spectroscopic data collected for both (Triphos)Fe(eta(4)-COT) complexes with data obtained for two appropriate reference compounds indicated that they possess a low-spin Fe(I) center that is antiferromagnetically coupled to a COT radical monoanion. Further evidence for this electronic structure determination by EPR spectroscopy and cyclic voltammetry is presented. A comparison of the solid-state metrical parameters determined in this study to those of related first-row transition-metal complexes has provided insight into the electronic structure analysis of related organometallic complexes.

• 出版日期2014-12-22
• 单位Los Alamos