Di-iron aza diphosphido complexes:: Mimics for the active site of Fe-only hydrogenase, and effects of changing the coordinating atoms of the bridging ligand in [Fe2{μ-(ECH2)2NR}(CO)6]

The bis(phosphido)-bridged complex [Fe-2(mu-PPhH)(2)(CO)(6)] (1) undergoes double deprotonation to give the phosphorus-centered dianionic derivative [Fe-2(mu-PPh)(2)(CO)(6)](2-) (2) which in turn reacts with the tertiary base RN(CH2Cl)(2) to give [Fe-2{(PPhCH2)(2)NR}-(CO)(6)] (3) in moderate yield. Treatment of 3 with HBF4.Et2O affords the N-protonated species [Fe-2{(PPhCH2)(2)NHR}(CO)(6)] BF4 (4). The structural changes to the heavy atom skeleton of 3 arising from protonation are slight, the most obvious being a ca. 0.03 Angstrom lengthening of the N-C bonds.The bis(phosphido)-bridged complex [Fe-2(mu-PPhH)(2)(CO)(6)] (1) undergoes double deprotonation to give the phosphorus-centered dianionic derivative [Fe-2(mu-PPh)(2)(CO)(6)](2-) (2) which in turn reacts with the tertiary base RN(CH2CI)(2) to give [Fe-2{1(PPhCH2)(2)NR}-(CO)(6)] (3) in moderate yield. Treatment of 3 with HBF4.Et2O affords the N-protonated species [Fe-2{(PPhCH2)(2)NHR}(CO)(6)] BF4 (4). The structural changes to the heavy atom skeleton of 3 arising from protonation are slight, the most obvious being a ca. 0.03 Angstrom lengthening of the N-C bonds.