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Published February 16, 2005 | Supplemental Material
Journal Article Open

Ground-State Singlet L_3Fe-(í-N)-FeL_3 and L_3Fe(NR) Complexes Featuring Pseudotetrahedral Fe(II) Centers

Abstract

Pseudotetrahedral iron(II) coordination complexes that contain bridged nitride and terminal imide linkages, and exhibit singlet ground-state electronic configurations, are described. Sodium amalgam reduction of the ferromagnetically coupled dimer, {[PhBP_]Fe(μ-1,3-N_3)}_2 (2) ([PhBP_3] = [PhB(CH_2PPh_2)_3]-), yields the diamagnetic bridging nitride species [{[PhBP_3]Fe}_2(μ-N)][Na(THF)_5] (3). The Fe−N−Fe linkage featured in the anion of 3 exhibits an unusually bent angle of approximately 135°, and the short Fe−N bond distances (Fe−N_(av) ≈ 1.70 Å) suggest substantial Fe−N multiple bond character. The diamagnetic imide complex {[PhBP_3]Fe^(II)_≡N(1-Ad)}{^nBu_4N} (4) has been prepared by sodium amalgam reduction of its low-spin iron(III) precursor, [PhBP_3]Fe^(III)_≡N(1-Ad) (5). Complexes 4 and 5 have been structurally characterized, and their respective electronic structures are discussed in the context of a supporting DFT calculation. Diamagnetic 4 provides a bona fide example of a pseudotetrahedral iron(II) center in a low-spin ground-state configuration. Comparative optical data strongly suggest that dinuclear 3 is best described as containing two high-spin iron(II) centers that are strongly antiferromagnetically coupled to give rise to a singlet ground-state at room temperature.

Additional Information

© 2005 American Chemical Society. Received August 4, 2004. Publication Date (Web): January 19, 2005. Financial support from the NSF (CHE-0132216), the DOE (PECASE), and the Alfred P. Sloan Foundation is gratefully acknowledged. We thank the Beckman Institute (Caltech) for use of the SQUID magnetometer, and Larry M. Henling and Theodore A. Betley for assistance with crystallographic studies. The Zewail group provided access to a Cary 500 UV/vis/NIR spectrophotometer.

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Supplemental Material - ja0453073si20040804_122827.pdf

Supplemental Material - ja0453073si20040804_122853.cif

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August 19, 2023
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