New C-functionalized propanedithiolate-type model complexes (1-8) have been synthesized by functional transformation reactions of the known complex [(mu-SCH2)(2)CH(OH)]Fe-2(CO)(6) (A). Treatment of A with the acylating agents PhC(O)Cl, 4-pyridinecarboxylic acid chloride, 2-furancarbonyl chloride, and 2-thiophenecarbonyl chloride in the presence of Et3N affords the expected C-functionalized complexes [(mu-SCH2)(2)CHO2CPh]Fe-2(CO)(6) (1), [(mu-SCH2)(2)CHO2CC5H4N-4]Fe-2(CO)(6) (2), [(mu-SCH2)(2)CHO2CC4H3O-2]Fe-2(CO)(6) (3), and [(mu-SCH2)(2)CHO2CC4H3S-2]Fe-2(CO)(6) (4). However, when A is treated with the phosphatizing agents Ph2PCl, PCl3 and PBr3, both C- and Fe-functionalized complexes[(mu-SCH2)(2)CHOPPh2-eta(1)]Fe-2(CO)(5) (5), [(mu-SCH2)(2)CHOPCl2-eta(1)]Fe-2(CO)(5) (6), and [(mu-SCH2)(2)CHOPBr2-eta(1)]Fe-2(CO)(5) (7) are unexpectedly obtained via intramolecular CO substitution by P atoms of the initially formed phosphite complexes. The simplest C-functionalized model complex [(mu-SCH2)(2)C=O]Fe-2(CO)(6) (8) can be produced by oxidation of A with Dess-Martin reagent. While 8 is found to be an electrocatalyst for proton reduction to hydrogen, starting complex A can be prepared by another method involving the reaction of HC(OH)(CH2Br)(2) with the in situ generated (mu-LiS)(2)Fe-2(CO)(6). X-ray crystallographic studies reveal that the bridgehead C atom of 8 is double-bonded to an 0 atom to form a ketone functionality, whereas the bridgehead C atoms of A, 1, 3, and 4 are equatorially-bonded to their functionalities and those of 5-7 axially-bonded to their functionalities due to formation of the corresponding P-Fe bond-containing heterocycles.