Ferrous Carbonyl Dithiolates as Precursors to FeFe, FeCo, and FeMn Carbonyl Dithiolates

Abstract

Reported are complexes of the formula Fe(dithiolate)(CO)2(diphos) and their use to prepare homo- and heterobimetallic dithiolato derivatives. The starting iron dithiolates were prepared by a one-pot reaction of FeCl2 and CO with chelating diphosphines and dithiolates, where dithiolate = S2(CH2)22- (edt2-), S2(CH2)32- (pdt2-), S2(CH2)2(C(CH3)2)2- (Me2pdt2-) and diphos = cis-C2H2(PPh2)2 (dppv), C2H4(PPh2)2 (dppe), C6H4(PPh2)2 (dppbz), C2H4[P(C6H11)2]2 (dcpe). The incorporation of 57Fe into such building block complexes commenced with the conversion of 57Fe into 57Fe2I4( i PrOH)4, which then was treated with K2pdt, CO, and dppe to give 57Fe(pdt)(CO)2(dppe). NMR and IR analyses show that these complexes exist as mixtures of all-cis and trans-CO isomers, edt2- favoring the former and pdt2- the latter. Treatment of Fe(dithiolate)(CO)2(diphos) with the Fe(0) reagent (benzylideneacetone)Fe(CO)3 gave Fe2(dithiolate)(CO)4(diphos), thereby defining a route from simple ferrous salts to models for hydrogenase active sites. Extending the building block route to heterobimetallic complexes, treatment of Fe(pdt)(CO)2(dppe) with [(acenaphthene)Mn(CO)3]+ gave [(CO)3Mn(pdt)Fe(CO)2(dppe)]+ ([3d(CO)]+). Reduction of [3d(CO)]+ with BH4- gave the Cs -symmetric μ-hydride (CO)3Mn(pdt)(H)Fe(CO)(dppe) (H3d). Complex H3d is reversibly protonated by strong acids, the proposed site of protonation being sulfur. Treatment of Fe(dithiolate)(CO)2(diphos) with CpCoI2(CO) followed by reduction by Cp2Co affords CpCo(dithiolate)Fe(CO)(diphos) (4), which can also be prepared from Fe(dithiolate)(CO)2(diphos) and CpCo(CO)2. Like the electronically related (CO)3Fe(pdt)Fe(CO)(diphos), these complexes undergo protonation to afford the μ-hydrido complexes [CpCo(dithiolate)HFe(CO)(diphos)]+. Low-temperature NMR studies indicate that Co is the kinetic site of protonation.

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