First‐Row Transition Metal Bis(amidinate) Complexes; Planar Four‐Coordination of Fe<sup>II</sup> Enforced by Sterically Demanding Aryl Substituents

Nijhuis, Christian A.; Jellema, Erica; Sciarone, Timo J. J.; Meetsma, Auke; Budzelaar, Peter H. M.; Hessen, Bart

doi:10.1002/ejic.200500094

Cited by 69 publications

(67 citation statements)

References 89 publications

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“…SP complexes are generally stabilized by anionic ligands with one or more following characteristics: (i) strong -donor ligands in order to destabilize the sterically stable tetrahedral geometry, (ii) weak -donating ligands to minimize the anti-bonding character of the dx²-y² orbital [18], (iii)sterically demanding ligands [75,76]. Magnetic anisotropy was investigated for several square-planar complexes [77][78][79][80].…”

Section: Square-planar Geometrymentioning

confidence: 99%

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

Bar

Pichon

Sutter

2016

Coordination Chemistry Reviews

377

249

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Section: Square-planar Geometrymentioning

confidence: 99%

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

Bar

Pichon

Sutter

2016

Coordination Chemistry Reviews

377

249

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“…Until the structure was confirmed [8] as tetrameric with octahedral coordination at the Co center, [Co(acac) 2 ] was postulated to have square-planar geometry based on magnetic and spectroscopic data that differed from tetrahedral complexes. [9] A search of the Cambridge Structural Database (V 5.32) [10] for Fe and Co complexes in a fourcoordinate environment with t 4 parameter [11] < 0.25 and magnetic susceptibility data revealed five high-spin d 6 Fe II complexes with macrocyclic or chelating N 4 [12,13] and O 4 [14,15] coordination, and three high-spin d 7 Co II complexes [12,16,17] with varied ligand systems. A complete description of the CSD search and results can be found in the Supporting Information.…”

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confidence: 99%

High‐Spin Square‐Planar Co^II and Fe^II Complexes and Reasons for Their Electronic Structure

et al. 2011

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More than half a century of intense investigation in coordination compounds has laid a firm foundation for our understanding of the ligand fields in transition-metal complexes. [1] Complexes of the heavier 4d and 5d metals are generally low spin, whereas the spin of 3d metal complexes can be high or low, depending on ligand characteristics. The number and type of donor atoms, ligand substituents, and the presence or absence of chelate rings all influence metal spin states. A combination of data-mining and detailed computational study have quantified recently these empirical observations. [2,3] In spite of such variety, there are still some types of metal complexes that are rarely observed.The stereospinomers [3] of high-spin, square-planar complexes, for example, are extremely rare because the large separation of the d [7] is known whose high-spin examples are subtly dependent on ligand substitution. Until the structure was confirmed [8] as tetrameric with octahedral coordination at the Co center, [Co(acac) 2 ] was postulated to have square-planar geometry based on magnetic and spectroscopic data that differed from tetrahedral complexes.[9] A search of the Cambridge Structural Database (V 5.32) [10] [22] Ni. [20] Spectroscopic [20] and computational [18] work have shown that these fluorinated ligands are medium field ligands, on par with OH À and F À , and stronger than NCO À . The electron-withdrawing power of extensively fluorinated ligands reduces the p-donor character of the O atom, such that bridging is not observed and mononuclear species are readily prepared.More recently, we have begun studies of the chelating perfluoropinacolate ligand, ddfp 2À . [23] Magnetic susceptibility and elemental analysis data were reported for K 2 [M(ddfp) 2 ], (M = Mn, Ni, Cu) for which square-planar geometry was proposed.[24] An octahedral bis-H 2 O adduct, (Me 4 N) 2 [Co-(OH 2 ) 2 (ddfp) 2 ] has been proposed based on elemental analysis data. [25] Despite the relative ease in making the [M(ddfp) 2 ] 2À complexes with first-row transition metals, no examples of M = Co II or Fe II have been published. We now report a highspin, square-planar Co II complex, {K(DME) 2 } 2 [Co(ddfp) 2 ] (1), and the analogous high-spin, square-planar Fe II complex {K(DME) 2 } 2 [Fe(ddfp) 2 ] (2). We also provide a discussion of three other square-planar {MO 4 } species from the recent literature whose composition and spin-state characteristics clarify the ligand requirements for the highly unusual highspin, square-planar combination in late row 3d metals.Compound 1 has been prepared as pale pink crystals as shown in Equation (1), and is stable in an inert atmosphere and in various organic solvents, but yields a brown oil upon prolonged exposure to air. Iron-containing 2, and the Zn II derivative, {K(DME) 2 } 2 [Zn(ddfp) 2 ] (3), were similarly prepared as purple-pink, and colorless crystals, respectively. No

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“…The use of o-disubstituted aryls 2,6-R 2 [4] and [ DippXyl L] 2 Fe (1b) [4] were prepared according to literature procedures. [Hz], integral, tentative assignment).…”

Section: Resultsmentioning

confidence: 99%

“…Dipp2 L] -and [ DippXyl L] -, homoleptic bis-(amidinate) complexes were isolated with an unusual planar geometry (Scheme 2), [4] whereas other structurally characterised homoleptic Fe II -bis(amidinates) invariantly exhibit tetrahedral geometries. [5][6][7][8][9] Scheme 1.…”

Section: Amidinates [(Rn)crј(nrјј)]mentioning

confidence: 99%

“…The groups of Gambarotta and Winter have demonstrated this for Cr II by using amidinates with simple alkyl or silyl substituents on the C and N atoms. For the bulkier N-substituents (CMe 3 or SiMe 3 ), the geometry of these d 4 complexes deviates from the planar situation found with smaller substituents (R = Cy, iPr). [1,2] By using o-disubstituted aryls on the N-donor atoms, Boeré characterised a highly unusual planar Mg-bis(amidinate).…”

Section: Amidinates [(Rn)crј(nrјј)]mentioning

confidence: 99%

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Reactivity of Paramagnetic Fe^II–Bis(amidinate) Complexes

et al. 2010

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Synthesis and characterisation of ether adducts of bis(amidinate) FeII complexes are described [amidinate = 2,6‐iPr2C6H3–NC(Ph)N–Ph]. The isolation of these five‐coordinate complexes contrasts with the homoleptic bis(amidinate) Fe complexes obtained previously with the sterically more demanding amidinate ligands 2,6‐iPr2C6H3–NC(Ph)N–Ar (Ar = 2,6‐iPr2C6H3, 2,6‐Me2C6H3) The more accessible ether adducts show enhanced reactivity towards Lewis bases and towards the π‐acid carbon monoxide. Reaction with excess amounts of CO results in carbonyl insertion into the Fe–N bonds, thereby giving rise to a diamagnetic bis(CO) adduct supported by two carbamoyl ligands.

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First‐Row Transition Metal Bis(amidinate) Complexes; Planar Four‐Coordination of Fe^II Enforced by Sterically Demanding Aryl Substituents

Cited by 69 publications

References 89 publications

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

High‐Spin Square‐Planar Co^II and Fe^II Complexes and Reasons for Their Electronic Structure

Reactivity of Paramagnetic Fe^II–Bis(amidinate) Complexes

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First‐Row Transition Metal Bis(amidinate) Complexes; Planar Four‐Coordination of FeII Enforced by Sterically Demanding Aryl Substituents

Cited by 69 publications

References 89 publications

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

High‐Spin Square‐Planar CoII and FeII Complexes and Reasons for Their Electronic Structure

Reactivity of Paramagnetic FeII–Bis(amidinate) Complexes

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First‐Row Transition Metal Bis(amidinate) Complexes; Planar Four‐Coordination of Fe^II Enforced by Sterically Demanding Aryl Substituents

High‐Spin Square‐Planar Co^II and Fe^II Complexes and Reasons for Their Electronic Structure

Reactivity of Paramagnetic Fe^II–Bis(amidinate) Complexes