Structural studies of nitroxyl ([TEMPO]n, [ABNO]n (n = 0,1)) ligation to iron reveal diversity in bonding (η1 vs. η2), oxygen atom transfer and aggregation

In attempts to generate complexes containing both nitroxyl and nitroxide ligands (TEMPO(0/−) or ABNO(0/−)), metathetical methods were employed with MnBr 2 (THF) 2 and various iron halides. While η 2 - and η 1 -TEMPO (or ABNO) were found to be the dominant binding motifs, deoxygenation proved to be a common path. A successful synthesis of {(η 2 -μ-O,N-TEMPO) 2 Na} 2 Mn ( 1 ) was realized, and the structure of {(η 2 -μ-O,N-TEMPO) 2 Na(TEMPO)}(TEMPO) 2 Fe ( 2 ) can be rationalized as having a nitroxyl bound to Na cation, in an Fe(III) complex whose total spin of S = 2 reflects an S = 5/2 core antiferromagnetically coupled to the nitroxyl. In one instance, the products of deoxygenation were contained in a diiron product, (TMP)(TEMPO) 5 (μ-O)Fe 2 Li 2 ( 5 , TMP = tetramethylpiperidide). In other cases, unprecedented aggregates formed as tentative formulations suggest they contain “[(TMP) 6 Fe(μ 3 -O)] 6 ” ( 3 ) and “{(TEMPO) 2 Na} 4 Fe 6 (μ 3 -O) 4 (μ 4 -O) 2 (TEMPO) 2 }” ( 4 ). [Na(ABNO)] 6 (THF) 4 (NaABNO) was crystallographically characterized as a pseudo hexamer of stacked cubes. Metathetic utilization of NaABNO afforded (ABNO) 6 (μ-O)Fe 2 Na 2 ( 7 ), and the ABN (9-azyl-bicyclo[3.3.1]nonane) unit coproduced was tentatively identified in the byproduct (η 2 -ABNO) 2 (ABNO)(ABN)Fe ( 6 ). While the goal of homoleptic nitroxyl/nitroxide complexes was unrealized, clearly these reagents are effective means of producing oxidic aggregates. • Near homoleptic nitroxyl complexes. • [Na(ABNO)] 6 (THF) 4 , a pseudo hexamer of stacked cubes. • Deoxgenation products. • Unique hexairon(III) clusters.