LIGAND SUBSTITUTION PROCESSES ON CARBONYLMETAL DERIVATIVES .2. REACTION OF TETRACARBONYLHYDRIDOFERRATES WITH PHOSPHITES

Ligand substitution processes m KHFe(CO)4 (1) have been evidenced by reaction with various phosphites. The nature of the reaction products strongly depends on (i) the nature of the solvent, (ii) the Tolman cone angle of the phosphite, and (iii) the reaction conditions. In protic media (H2O-THF), phosphites with small cone angles, such as P(OMe)3, P(OEt)3, and P(OPh)3, react (2 equiv) with 1 at room temperature to give the corresponding complexes H2Fe(CO)2[P(OR)3]2 in > 90% yield, whereas a phosphite with a larger cons angle (P[O-o-C6H4Ph]3) reacts only at a higher temperature to afford the disubstituted Fe(CO)3[P{O-o-C6H4Ph}3]2 derivative in 94% yield. When the reaction with phosphites having small cone angles is conducted with a 3-fold excess of phosphite at 65-degree-C, the trisubtituted derivatives Fe(CO)2[P(OR)3]3 are formed in 75-96% yield. In aprotic medium (THF), 1 reacts with phosphites (2 equiv) at room temperature to yield the monosubstituted anionic hydrides K+[HFe(CO)3{P(OR)3}]-, which can be isolated in > 90% yield. In refluxing THF the reaction of 1 with P(OMe)3 (3 equiv) demonstrates the first synthesis of the hydridoferrate K+[HFe(CO)2{P(OMe)3}2]-. Protonation of K+[HFe(CO)3{P(OR)3}]-with trifluoroacetic acid in THF at -10-degrees-C provides an excellent route for the high-yield synthesis of the monosubstituted dihydrides H2Fe(CO)3[P(OR)3]. In situ reaction of the latter with another phosphane PZ3 (Z = Ph, OPh) leads to the mixed dihydrides H2Fe(CO)2[P(OR)3][PZ3] (R = Me, Et; Z = Ph, OPh), which are reported for the first time. Finally, reaction of H2Fe(CO)2[P(OEt)3]2 with KH under sonication allows the generation of the highly reduced derivative K2[Fe(CO)2{P(OEt)3}2], the first disubstituted analogue of the Collman reagent.