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Published on: October 18, 2018
Unravelling the Photochemical Transformations of Chromium(I) 1,3 Bis(diphenylphosphino), [Cr(CO)4(dppp)]+, by EPR
Stephen L J Luckham1,2, Andrea Folli1, James A Platts1
1School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, U.K.
Abstract:
UV-induced photochemical transformations of the paramagnetic [Cr(CO)4(Ph2PCH2CH2CH2PPh2)]+ complex (abbreviated [Cr(CO)4(dppp)]+) in dichloromethane was investigated by CW EPR spectroscopy. Room-temperature UV irradiation results in the rapid transformation of [Cr(CO)4(dppp)]+ into trans-[Cr(CO)2(dppp)2]+. However, low-temperature (77-120 K) UV irradiation reveals the presence of an intermediate mer-[Cr(CO)3(κ1-dppp)(κ2-dppp)]+ complex which photochemically transforms into trans-[Cr(CO)2(dppp)2]+. The derived spin Hamiltonian parameters for these complexes were confirmed by DFT calculations. The photoinduced reaction is shown to be concentration-dependent, leading to a distribution of the three complexes ([Cr(CO)4(dppp)]+, mer-[Cr(CO)3(κ1-dppp)(κ 2-dppp)]+, and trans-[Cr(CO)2(dppp)2]+). A bimolecular photoinduced mechanism is proposed to account for the formation of mer-[Cr(CO)3(κ1-dppp)(κ2-dppp)]+ and trans-[Cr(CO)2(dppp)2]+.
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