Organometallic polymers assembled from cation-p interactions: use of ferrocene as a ditopic linker within the homologous series[{(Me3Si)2NM}2·ACHTUNGTRENUNG(Cp2Fe)]1(M=Na, K, Rb, Cs; Cp=cyclopentadienyl)

J. Jacob Morris, B.C. Noll, Gordon William Honeyman, C.T. O'Hara, A.R. Kennedy, R.E. Mulvey, K Henderson

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Abstract

Addition of ferrocene to solutions of alkali metal hexamethyldisilazides M(HMDS) in arenes (in which M=Na, K, Rb, Cs) allows the subsequent crystallization of the homologous series of compounds [{(Me3Si)2NM}2 (Cp2Fe)]∞ (1–4). Similar reactions using LiHMDS led to the recrystallization of the starting materials. The crystal structures of 1–4 reveal the formation of one-dimensional chains composed of dimeric [{M(HMDS)}2] aggregates, which are bridged through neutral ferrocene molecules by η5-cation–π interactions. In addition, compounds 3 and 4 also contain interchain agostic MC interactions, producing two-dimensional 44-nets. Whereas 1 and 2 were prepared from toluene, the syntheses of 3 and 4 required the use of tert-butylbenzene as the reaction media. The attempted crystallization of 3 and 4 from toluene resulted in formation of the mixed toluene/ferrocene solvated complexes [{(Me3Si)2NM)2}2 (Cp2Fe)x(Tol)y]∞ (in which M=Rb, x=0.6, y=0.8, 5; M=Cs, x=0.5, y=1, 6). The extended solid-state structures of 5 and 6 are closely related to the 44-sheets 3 and 4, but are now assembled from a combination of cation–π, agostic, and π–π interactions. The charge-separated complex [K{(C6H6)2Cr}1.5(Mes)][Mg(HMDS)3] (15) was also structurally characterized and found to adopt an anionic two-dimensional 63-network through doubly η3-coordinated bis(benzene)chromium molecules. DFT calculations at the B3 LYP/6–31G* level of theory indicate that the binding energies of both ferrocene and toluene to the M(HMDS) dimers increases in the sequence Li<Na<K. This pattern is a consequence of the larger metals allowing more open coordination spheres to support cation–π contacts. By comparison, binding of the isolated metal cations to the aromatic groups follow the reverse order K<Na<Li. A combined analysis of theoretical and experimental data suggest that ferrocene is a stronger cation–π donor than toluene for the lighter metals, but that this difference is eliminated on descending the group.
LanguageEnglish
Pages4418-4432
Number of pages15
JournalChemistry - A European Journal
Volume13
Issue number16
DOIs
Publication statusPublished - 25 May 2007

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Toluene
Organometallics
Cations
Polymers
Metals
Crystallization
Alkali Metals
Molecules
Chromium
Benzene
Binding energy
Discrete Fourier transforms
Dimers
Crystal structure
ferrocene

Keywords

  • alkali metals
  • metallocenes
  • noncovalent interactions
  • pi interactions
  • self-assembly

Cite this

@article{0a14394104d44823a0305e678e6c2b66,
title = "Organometallic polymers assembled from cation-p interactions: use of ferrocene as a ditopic linker within the homologous series[{(Me3Si)2NM}2·ACHTUNGTRENUNG(Cp2Fe)]1(M=Na, K, Rb, Cs; Cp=cyclopentadienyl)",
abstract = "Addition of ferrocene to solutions of alkali metal hexamethyldisilazides M(HMDS) in arenes (in which M=Na, K, Rb, Cs) allows the subsequent crystallization of the homologous series of compounds [{(Me3Si)2NM}2 (Cp2Fe)]∞ (1–4). Similar reactions using LiHMDS led to the recrystallization of the starting materials. The crystal structures of 1–4 reveal the formation of one-dimensional chains composed of dimeric [{M(HMDS)}2] aggregates, which are bridged through neutral ferrocene molecules by η5-cation–π interactions. In addition, compounds 3 and 4 also contain interchain agostic MC interactions, producing two-dimensional 44-nets. Whereas 1 and 2 were prepared from toluene, the syntheses of 3 and 4 required the use of tert-butylbenzene as the reaction media. The attempted crystallization of 3 and 4 from toluene resulted in formation of the mixed toluene/ferrocene solvated complexes [{(Me3Si)2NM)2}2 (Cp2Fe)x(Tol)y]∞ (in which M=Rb, x=0.6, y=0.8, 5; M=Cs, x=0.5, y=1, 6). The extended solid-state structures of 5 and 6 are closely related to the 44-sheets 3 and 4, but are now assembled from a combination of cation–π, agostic, and π–π interactions. The charge-separated complex [K{(C6H6)2Cr}1.5(Mes)][Mg(HMDS)3] (15) was also structurally characterized and found to adopt an anionic two-dimensional 63-network through doubly η3-coordinated bis(benzene)chromium molecules. DFT calculations at the B3 LYP/6–31G* level of theory indicate that the binding energies of both ferrocene and toluene to the M(HMDS) dimers increases in the sequence Li<Na<K. This pattern is a consequence of the larger metals allowing more open coordination spheres to support cation–π contacts. By comparison, binding of the isolated metal cations to the aromatic groups follow the reverse order K<Na<Li. A combined analysis of theoretical and experimental data suggest that ferrocene is a stronger cation–π donor than toluene for the lighter metals, but that this difference is eliminated on descending the group.",
keywords = "alkali metals, metallocenes, noncovalent interactions, pi interactions, self-assembly",
author = "Morris, {J. Jacob} and B.C. Noll and Honeyman, {Gordon William} and C.T. O'Hara and A.R. Kennedy and R.E. Mulvey and K Henderson",
year = "2007",
month = "5",
day = "25",
doi = "10.1002/chem.200700219",
language = "English",
volume = "13",
pages = "4418--4432",
journal = "Chemistry - A European Journal",
issn = "0947-6539",
number = "16",

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TY - JOUR

T1 - Organometallic polymers assembled from cation-p interactions

T2 - Chemistry - A European Journal

AU - Morris, J. Jacob

AU - Noll, B.C.

AU - Honeyman, Gordon William

AU - O'Hara, C.T.

AU - Kennedy, A.R.

AU - Mulvey, R.E.

AU - Henderson, K

PY - 2007/5/25

Y1 - 2007/5/25

N2 - Addition of ferrocene to solutions of alkali metal hexamethyldisilazides M(HMDS) in arenes (in which M=Na, K, Rb, Cs) allows the subsequent crystallization of the homologous series of compounds [{(Me3Si)2NM}2 (Cp2Fe)]∞ (1–4). Similar reactions using LiHMDS led to the recrystallization of the starting materials. The crystal structures of 1–4 reveal the formation of one-dimensional chains composed of dimeric [{M(HMDS)}2] aggregates, which are bridged through neutral ferrocene molecules by η5-cation–π interactions. In addition, compounds 3 and 4 also contain interchain agostic MC interactions, producing two-dimensional 44-nets. Whereas 1 and 2 were prepared from toluene, the syntheses of 3 and 4 required the use of tert-butylbenzene as the reaction media. The attempted crystallization of 3 and 4 from toluene resulted in formation of the mixed toluene/ferrocene solvated complexes [{(Me3Si)2NM)2}2 (Cp2Fe)x(Tol)y]∞ (in which M=Rb, x=0.6, y=0.8, 5; M=Cs, x=0.5, y=1, 6). The extended solid-state structures of 5 and 6 are closely related to the 44-sheets 3 and 4, but are now assembled from a combination of cation–π, agostic, and π–π interactions. The charge-separated complex [K{(C6H6)2Cr}1.5(Mes)][Mg(HMDS)3] (15) was also structurally characterized and found to adopt an anionic two-dimensional 63-network through doubly η3-coordinated bis(benzene)chromium molecules. DFT calculations at the B3 LYP/6–31G* level of theory indicate that the binding energies of both ferrocene and toluene to the M(HMDS) dimers increases in the sequence Li<Na<K. This pattern is a consequence of the larger metals allowing more open coordination spheres to support cation–π contacts. By comparison, binding of the isolated metal cations to the aromatic groups follow the reverse order K<Na<Li. A combined analysis of theoretical and experimental data suggest that ferrocene is a stronger cation–π donor than toluene for the lighter metals, but that this difference is eliminated on descending the group.

AB - Addition of ferrocene to solutions of alkali metal hexamethyldisilazides M(HMDS) in arenes (in which M=Na, K, Rb, Cs) allows the subsequent crystallization of the homologous series of compounds [{(Me3Si)2NM}2 (Cp2Fe)]∞ (1–4). Similar reactions using LiHMDS led to the recrystallization of the starting materials. The crystal structures of 1–4 reveal the formation of one-dimensional chains composed of dimeric [{M(HMDS)}2] aggregates, which are bridged through neutral ferrocene molecules by η5-cation–π interactions. In addition, compounds 3 and 4 also contain interchain agostic MC interactions, producing two-dimensional 44-nets. Whereas 1 and 2 were prepared from toluene, the syntheses of 3 and 4 required the use of tert-butylbenzene as the reaction media. The attempted crystallization of 3 and 4 from toluene resulted in formation of the mixed toluene/ferrocene solvated complexes [{(Me3Si)2NM)2}2 (Cp2Fe)x(Tol)y]∞ (in which M=Rb, x=0.6, y=0.8, 5; M=Cs, x=0.5, y=1, 6). The extended solid-state structures of 5 and 6 are closely related to the 44-sheets 3 and 4, but are now assembled from a combination of cation–π, agostic, and π–π interactions. The charge-separated complex [K{(C6H6)2Cr}1.5(Mes)][Mg(HMDS)3] (15) was also structurally characterized and found to adopt an anionic two-dimensional 63-network through doubly η3-coordinated bis(benzene)chromium molecules. DFT calculations at the B3 LYP/6–31G* level of theory indicate that the binding energies of both ferrocene and toluene to the M(HMDS) dimers increases in the sequence Li<Na<K. This pattern is a consequence of the larger metals allowing more open coordination spheres to support cation–π contacts. By comparison, binding of the isolated metal cations to the aromatic groups follow the reverse order K<Na<Li. A combined analysis of theoretical and experimental data suggest that ferrocene is a stronger cation–π donor than toluene for the lighter metals, but that this difference is eliminated on descending the group.

KW - alkali metals

KW - metallocenes

KW - noncovalent interactions

KW - pi interactions

KW - self-assembly

U2 - 10.1002/chem.200700219

DO - 10.1002/chem.200700219

M3 - Article

VL - 13

SP - 4418

EP - 4432

JO - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

IS - 16

ER -