10.1021/ic061344e.s002 Celedonio M. Alvarez Celedonio M. Alvarez M. Angeles Alvarez M. Angeles Alvarez María Alonso María Alonso M. Esther García M. Esther García M. Teresa Rueda M. Teresa Rueda Miguel A. Ruiz Miguel A. Ruiz Patrick Herson Patrick Herson Trapping of Hemiquinone Radicals at Mo and P Sites by Phosphide-Bridged Dimolybdenum Species:  Chemistry of Complexes [Mo<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>(OC<sub>6</sub>H<sub>4</sub>OH)(μ-PR<sub>2</sub>)(CO)<sub>4</sub>] and [Mo<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>{μ-PR(OC<sub>6</sub>H<sub>4</sub>OH)}(CO)<sub>4</sub>]<sup>-</sup> (R = Cy, Ph) American Chemical Society 2006 OH DBU ER cyclohexyl anion experiences OC 4H OPh complex Mo 2Cp Mo 2Cp displays 2006-11-13 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Trapping_of_Hemiquinone_Radicals_at_Mo_and_P_Sites_by_Phosphide_Bridged_Dimolybdenum_Species_Chemistry_of_Complexes_Mo_sub_2_sub_sup_5_sup_C_sub_5_sub_H_sub_5_sub_sub_2_sub_OC_sub_6_sub_H_sub_4_sub_OH_PR_sub_2_sub_CO_sub_4_sub_and_Mo_sub_2_sub_sup_5_sup_C/3048487 The phosphide-bridged dimolybdenum complexes (H-DBU)[Mo<sub>2</sub>Cp<sub>2</sub>(μ-PR<sub>2</sub>)(CO)<sub>4</sub>] (R= Cy, Ph; DBU = 1,8-diazabicyclo[5.4.0.]undec-7-ene) react with <i>p</i>-benzoquinone to give the hemiquinone complexes [Mo<sub>2</sub>Cp<sub>2</sub>(OC<sub>6</sub>H<sub>4</sub>OH)(μ-PR<sub>2</sub>)(CO)<sub>4</sub>]. The latter experience facile homolytic cleavage of the corresponding Mo−O bonds and react readily at room temperature with HSPh or S<sub>2</sub>Ph<sub>2</sub> to give the thiolate complexes [Mo<sub>2</sub>Cp<sub>2</sub>(μ-PCy<sub>2</sub>)(μ-SPh)(CO)<sub>4</sub>] or [Mo<sub>2</sub>Cp<sub>2</sub>(μ-PR<sub>2</sub>)(μ-SPh)(CO)<sub>2</sub>]. In contrast, PRH-bridged substrates experience overall insertion of quinone into the P−H bond to give the anionic compounds (H-DBU)[Mo<sub>2</sub>Cp<sub>2</sub>{μ-PR(OC<sub>6</sub>H<sub>4</sub>OH)}(CO)<sub>4</sub>], which upon acidification yield the corresponding neutral hydrides. The cyclohexyl anion experiences rapid nucleophilic displacement of the hemiquinone group by different anions ER<sup>-</sup> (ER = OH, OMe, OC<sub>4</sub>H<sub>5</sub>, OPh, SPh) to give novel anionic compounds (H-DBU)[Mo<sub>2</sub>Cp<sub>2</sub>{μ-PCy(ER)}(CO)<sub>4</sub>], which upon acidification yield the corresponding neutral hydrides. The structure of four of these hydride complexes [PPh(OC<sub>6</sub>H<sub>4</sub>OH), PCy(OH), PCy(OMe), and PCy(OPh) bridges] was determined by X-ray diffraction methods and confirmed the presence of cis and trans isomers in several of these complexes. In addition, it was found that the hydroxyphosphide anion [Mo<sub>2</sub>Cp<sub>2</sub>{μ-PCy(OH)}(CO)<sub>4</sub>]<sup>-</sup> displays in solution an unprecedented tautomeric equilibrium with its hydride-oxophosphinidene isomer [Mo<sub>2</sub>Cp<sub>2</sub>(μ-H){μ-PCy(O)}(CO)<sub>4</sub>]<sup>-</sup>.