{"doi":"10.1021/jacs.3c03352","title":"Highly Selective Fe-Catalyzed Nitrogen Fixation to Hydrazine Enabled by Sm(II) Reagents with Tailored Redox Potential and p<i>K</i><sub>a</sub>","abstract":"Controlling product selectivity in multiproton, multielectron reductions of unsaturated small molecules is of fundamental interest in catalysis. For the N 2 reduction reaction (N 2 RR) in particular, parameters that dictate selectivity for either the 6H + /6e – product ammonia (NH 3 ) or the 4H + /4e – product hydrazine (N 2 H 4 ) are poorly understood. To probe this issue, we have developed conditions to invert the selectivity of a tris(phosphino)borane iron catalyst ( Fe ), with which NH 3 is typically the major product of N 2 R, to instead favor N 2 H 4 as the sole observed fixed-N product (>99:1). This dramatic shift is achieved by replacing moderate reductants and strong acids with a very strongly reducing but weakly acidic Sm II –(2-pyrrolidone) core supported by a hexadentate dianionic macrocyclic ligand ( Sm II –PH) as the net hydrogen-atom donor. The activity and efficiency of the catalyst with this reagent remain high (up to 69 equiv of N 2 H 4 per Fe and 67% fixed-N yield per H + ). However, by generating N 2 H 4 as the kinetic product, the overpotential of this Sm-driven reaction is 700 mV lower than that of the mildest reported set of NH 3 -selective conditions with Fe . Mechanistic data support assignment of iron hydrazido(2−) species FeNNH 2 as selectivity-determining: we infer that protonation of FeNNH 2 at N β, favored by strong acids, releases NH 3, whereas one-electron reduction to FeNNH 2 –, favored by strong reductants such as Sm II –PH, produces N 2 H 4 via reactivity initiated at N α . Spectroscopic data also implicate a role for Sm III -binding to anionic Fe N 2 – (via an Fe –N 2 - - Sm III species) with respect to catalytic efficacy.","journal":"Journal of the American Chemical Society","year":2023,"id":332827,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":24,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9561,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2023-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":25233,"name":"Jonas C. Peters","orcid":"0000-0002-6610-4414","position":1,"is_corresponding":false},{"id":832083,"name":"Emily A. Boyd","orcid":"0000-0003-0150-5396","position":0,"is_corresponding":true}],"reference_count":57,"raw_metadata":null,"created_at":"2026-07-19T01:09:35.125543Z","pmid":"37376713","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}