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

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 FeCl 2 and CO with chelating diphosphines and dithiolates, where dithiolate = S 2 (CH 2 ) 2 2- (edt 2- ), S 2 (CH 2 ) 3 2- (pdt 2- ), S 2 (CH 2 ) 2 (C(CH 3 ) 2 ) 2- (Me 2 pdt 2- ) and diphos = cis -C 2 H 2 (PPh 2 ) 2 (dppv), C 2 H 4 (PPh 2 ) 2 (dppe), C 6 H 4 (PPh 2 ) 2 (dppbz), C 2 H 4 [P(C 6 H 11 ) 2 ] 2 (dcpe). The incorporation of 57 Fe into such building block complexes commenced with the conversion of 57 Fe into 57 Fe 2 I 4 ( i PrOH) 4 , which then was treated with K 2 pdt, CO, and dppe to give 57 Fe(pdt)(CO) 2 (dppe). NMR and IR analyses show that these complexes exist as mixtures of all-cis and trans-CO isomers, edt 2- favoring the former and pdt 2- the latter. Treatment of Fe(dithiolate)(CO) 2 (diphos) with the Fe(0) reagent (benzylideneacetone)Fe(CO) 3 gave Fe 2 (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) 3 Mn(pdt)Fe(CO) 2 (dppe)] + ([ 3d (CO)] + ). Reduction of [ 3d (CO)] + with BH 4 - gave the C s -symmetric μ-hydride (CO) 3 Mn(pdt)(H)Fe(CO)(dppe) (H 3d ). Complex H 3d is reversibly protonated by strong acids, the proposed site of protonation being sulfur. Treatment of Fe(dithiolate)(CO) 2 (diphos) with CpCoI 2 (CO) followed by reduction by Cp 2 Co 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) 3 Fe(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.