Topological Variations of the PDP Ligand and Its Prospects in Molybdenum(0) Dearomatization Agents

The compounds fac-(κ3-PDP)Mo(CO)3 {1; PDP = 2-[[2-(1-(pyridin-2-ylmethyl)pyrrolidin-2-yl)pyrrolidin-1-yl]methyl]pyridine}, [(cis-β-PDP)Mo(NO)(CO)]PF6 ([cis-β-3]PF6), [(cis-α-PDP)Mo(NO)(CO)]PF6 ([cis-α-3]PF6), [(cis-α-PDP)Mo(NO)Br]PF6 ([4]PF6), [(trans-PDP)Cu](BF4)2·CH3CN ([5](BF4)2·CH3CN), and [(trans-PDP)Cu](OSO2CF3)2 ([5](OSO2CF3)2) have been synthesized and structurally characterized by single-crystal X-ray diffraction. These are the first reported complexes of PDP on metal centers other than iron(II). The observed configurations indicate a broader range of accessible PDP topologies than has been reported. The {(cis-α-PDP)Mo(NO)}+ fragment is found to be less π-basic than the dearomatizing {Tp(MeIm)Mo(NO)} fragment [Tp = hydridotris(1-pyrazolyl)borato; MeIm = 1-methylimidazole].