New Class of Hydrido Iron(II) Compounds with Cis Reactive Sites: Combination of Iron and Diphosphinodithio Ligand

The cationic complex [Fe(P2S2)(NCMe)2]2+ (P2S2 = (Ph2PC6H4CH2S)2(C2H4), [1(NCMe)2]2+) with two MeCN ligands in a cis orientation was synthesized and characterized. The MeCN ligand in [1(NCMe)2]2+ undergoes further substitution by hydride ligand or CO to give iron(II) hydrides [H1(NCMe)]+, [H1H]0 and [H1(CO)]+ respectively. The reactivity of the hydrides goes from [H1H]0 > [H1(NCMe)]+ > [H1(CO)]+, and was illustrated by their reactions toward protic acids, the organic cation of 10-methylacridinium (MeAcr+) as a hydride acceptor, and intermolecular hydride transfer reactions among these ferrous compounds. For example, MeAcr+ was reduced initially by a one-electron transfer process from [H1H]0 resulting in competing reactions of MeAcr* dimerization, HAT from [H1H]+ to MeAcr*, and decomposition of [H1H]+; MeAcrH was produced in excellent yields via a "single-step H-" transfer from [H1(NCMe)]+ to MeAcr+ but [H1(CO)]+ is inactive toward MeAcr+.