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Spin-State Tuning at Pseudotetrahedral d^7 Ions: Examining the Structural and Magnetic Phenomena of Four-Coordinate [BP_3]Co^(II)-X Systems

Jenkins, David M. and Peters, Jonas C. (2005) Spin-State Tuning at Pseudotetrahedral d^7 Ions: Examining the Structural and Magnetic Phenomena of Four-Coordinate [BP_3]Co^(II)-X Systems. Journal of the American Chemical Society, 127 (19). pp. 7148-7165. ISSN 0002-7863.

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Electronic structure, spin-state, and geometrical relationships for a series of pseudotetrahedral Co(II) aryloxide, siloxide, arylthiolate, and silylthiolate complexes supported by the tris(phosphino)borate [BP_3] ligands [PhBP_3] and [PhBP^(iPr)_3] ([PhB(CH_2PPh_2)_3]^- and [PhB(CH_2PiPr_2)_3]^-, respectively) are described. Standard ^1H NMR, optical, electrochemical, and solution magnetic data, in addition to low-temperature EPR and variable temperature SQUID magnetization data, are presented for the new cobalt(II) complexes [PhBP_3]CoOSiPh_3 (2), [PhBP_3]CoO(4-^tBu-Ph) (3), [PhBP_3]CoO(C_6F_5) (4), [PhBP_3]CoSPh (5), [PhBP_3]CoS(2,6-Me_2-Ph) (6), [PhBP_3]CoS(2,4,6-iPr_3-Ph) (7), [PhBP_3]CoS(2,4,6-^tBu_3-Ph) (8), [PhBP_3]CoSSiPh_3 (9), [PhBP_3]CoOSi(4-NMe_2-Ph)_3 (10), [PhBP_3]CoOSi(4-CF_3-Ph)_3 (11), [PhBP_3]CoOCPh_3 (12), [PhBPiPr_3]CoOSiPh_3 (14), and [PhBPiPr_3]CoSSiPh_3 (15). The low-temperature solid-state crystal structures of 2, 3, 5−10, 12, and 15 are also described. These pseudotetrahedral cobalt(II) complexes are classified as featuring one of two limiting distortions, either umbrella or off-axis. Magnetic and spectroscopic data demonstrate that both S = 1/2 and S = 3/2 ground-state electronic configurations are accessible for the umbrella distorted structure type, depending on the nature of the X-type ligand, its denticity (η^1 versus η^3), and the tripodal phosphine ligand employed. Off-axis distorted complexes populate an S = 1/2 ground-state exclusively. For those four-coordinate complexes that populate S = 1/2 ground states, X-ray data show two Co−P bond distances that are invariably shorter than a third Co−P bond. The pseudotetrahedral siloxides 2, 10, and 11 are exceptional in that they display gradual spin crossover in the solid state. The diamagnetic cobalt(III) complex {[PhBP_3]CoOSiPh_3}{BAr_4} ({16}{BAr_4}) (Ar = Ph or 3,5-(CF_3)_2−C_6H_3) has also been prepared and structurally characterized. Accompanying electronic structure calculations (DFT) for complexes 2, 6, and {16}^+ support the notion of a close electronic structure relationship between these four-coordinate systems and octahedral, sandwich, and half-sandwich coordination complexes.

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Peters, Jonas C.0000-0002-6610-4414
Alternate Title:Spin-State Tuning at Pseudotetrahedral d7 Ions: Examining the Structural and Magnetic Phenomena of Four-Coordinate [BP3]Co(II)-X Systems
Additional Information:© 2005 American Chemical Society. Received August 3, 2004. Publication Date (Web): April 20, 2005. Financial support from the NSF (CHE-0132216), the DOE (PECASE), and the Alfred P. Sloan Foundation is gratefully acknowledged. D.M.J. was supported by an NSF predoctoral fellowship. The Beckman Institute (Caltech) provided access to a SQUID magnetometer, and the Zewail lab provided access to a NIR spectrophotometer. Dr. Michael Day and Larry Henling provided crystallographic assistance, and Dr. Angel Di Bilio provided EPR assistance. Finally, we are very grateful to Dr. Santiago Alvarez and Jordi Cirera (Universitat de Barcelona, Spain) for help with the continuous symmetry measurement analysis and a stimulating scientific exchange.
Funding AgencyGrant Number
Department of Energy (DOE) PECASEUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
NSF Predoctoral FellowshipUNSPECIFIED
Issue or Number:19
Record Number:CaltechAUTHORS:20140805-084117047
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Official Citation:Spin-State Tuning at Pseudotetrahedral d7 Ions:  Examining the Structural and Magnetic Phenomena of Four-Coordinate [BP3]CoII−X Systems David M. Jenkins and and Jonas C. Peters Journal of the American Chemical Society 2005 127 (19), 7148-7165
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47958
Deposited By: Ruth Sustaita
Deposited On:05 Aug 2014 16:23
Last Modified:26 Nov 2019 11:15

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