Advances in alkaline earth-nitrogen chemistry

Torvisco, Ana; O'Brien, Anna; Ruhlandt‐Senge, Karin

doi:10.1016/j.ccr.2011.02.015

Cited by 97 publications

(66 citation statements)

References 171 publications

(256 reference statements)

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“…Side-on coordination has already been observed when oligomerization of the complexes occurred, but this coordination behavior was restricted to the heaviest alkaline earth metals [8]. Aggregation with the lighter s-block metal atoms lithium and calcium as well as zinc was always encountered with Table 1.…”

Section: Molecular Structuresmentioning

confidence: 96%

3-Phenyl-5-(2-pyridyl)pyrazolato Complexes of Lithium, Magnesium, Calcium, and Zinc

Kloubert¹,

Görls²,

Westerhausen³

2012

Zeitschrift Für Naturforschung B

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Metalation of 3-phenyl-5-(2-pyridyl)pyrazole (HPz, 1) with alkyllithium and -zinc compounds in tetrahydrofuran (thf) yields dinuclear products [(thf)Li(Pz)] 2 (2) and [MeZn(Pz)] 2 (3), respectively. Magnesiation of 1 with diethylmagnesium in tetrahydrofuran in the presence of 1,4-dioxane leads to cocrystallization of mononuclear [(thf) 2 Mg(Pz) 2 ] (4a) and [(diox) 2 Mg(Pz) 2 ] (4b). Metalation of 1 with KH followed by a metathesis reaction with CaI 2 in tetrahydrofuran leads to the formation of dinuclear [{(thf) 2 Ca}(µ-Pz) 3 Ca(Pz)] (5) with the calcium atoms in different coordination environments. The ligand precursor 1 crystallizes as a dimer with N-H· · ·N bridges between the pyrazole fragments. The pyrazolate anions of the metal complexes 2 to 5 exhibit similar structural parameters regardless of a bridging or terminal coordination mode and the electronegativity of the coordinated metal.

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Section: Molecular Structuresmentioning

confidence: 96%

3-Phenyl-5-(2-pyridyl)pyrazolato Complexes of Lithium, Magnesium, Calcium, and Zinc

Kloubert¹,

Görls²,

Westerhausen³

2012

Zeitschrift Für Naturforschung B

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“…The presence of a sterically demanding spectator ligand helps to stabilise the Ae metal centre against lability and brings to the fore the importance of Ae···π, Ae···H-X and CH···π interactions. 16,38,39,[40][41][42] Such interactions have previously been overlooked due to difficulties in synthetic procedures as a consequence of high reactivity. 43 As a corollary, these interactions have also been largely ignored computationally.…”

Section: Resultsmentioning

confidence: 99%

“…These interactions are competitive, as Ca···π interactions are known to exhibit comparable energies to dative interactions. [40][41][42] Moreover, we have shown here that the alkylphosphine moiety can coordinate interchangeably between these modes (CaP and Ca···π). Energy profiles corresponding to a rotation about the C b -P bond leading to substitution of the CaP for a Ca···π (PhP1) (blue) interaction, as well as a rotation about the C a -C b bond leading to deactivation of the CaP interaction (red) are presented in Figure 9.…”

Section: Alkene Insertion Productsmentioning

confidence: 99%

“…[40][41][42] The most well documented non-covalent bonding motif is the cation···π interaction, involving a strong electrostatic attraction between a positively charged cation and the p electron density of an aromatic system. Cation···π interactions play a fundamental role in biomolecular structure and in materials chemistry.…”

Section: Role Of Fluxional Bonding Interactionsmentioning

confidence: 99%

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Hydrophosphination of Styrene and Polymerization of Vinylpyridine: A Computational Investigation of Calcium-Catalyzed Reactions and the Role of Fluxional Noncovalent Interactions

Ward

Hunt

2016

ACS Catal.

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A computational investigation of the intermolecular hydrophosphination of styrene and 2-vinylpyridine, catalysed by the heteroleptic b-diketiminato-stabilised calcium complex [(PhNC(Me)CHC(Me)NPh)CaPPh2], is presented. Alkene insertion does not proceed via the traditional route as proposed by experimental and theoretical research related to intermolecular hydroamination catalysed by alkaline earth or lanthanide complexes. In contrast, for the hydrophosphination mechanism, insertion proceeds via an outer sphere, conjugative addition where there is no direct interaction of Ca with the vinyl functionality. Following the initial rate determining alkene insertion, two distinct mechanisms emerge, protonolysis or polymerisation. Polymerisation of styrene is energetically less favourable than protonolysis whereas the reverse is determined for 2-vinylpyridine, thereby providing strong evidence for outcomes observed experimentally. The vinylarene ring is important as it allows for preferential coordination of the unsaturated substrate through numerous non-covalent Ca···π, CH···π and CaE (E=P, N) interactions, moreover the vinylarene ring counteracts unfavourable charge localisation within the activated transition state. The additional stability of the CaN over CaP dative interaction in vinylpyridine provides a rationalisation for the experimentally observed enhanced reactivity of vinylpyridine, particularly in the context of the almost identical local alkene insertion barriers. Previously, little emphasis has been placed on the involvement of non-covalent interactions however, our calculations reveal that Ca···π, CH···π and Cadonor interactions are critical; stabilising key intermediates and transition states, while also introducing numerous competitive pathways.

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“…Recently, related compounds Me 2 Si(NDipp) 2 Ae(thf) n (Ae = alkaline earth metal) were reported containing a bidentate bis(amido)silane backbone [21]. Decreasing steric demand of the anilido ligands leads from monomeric [(thf) 4 [25].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Strontium Bis(N-isopropylanilide) and Comparison with the Lighter Magnesium and Calcium Congeners

Loh

Glock

Ziemann

et al. 2013

Zeitschrift Für Naturforschung B

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The metathesis reaction of strontium diiodide [(thf) (9) can be isolated. Reaction of this complex with 1,2-dimethoxyethane or metalation of N-isopropylaniline with dibutylmagnesium in DME yield the dme adduct, [(dme)Mg{N(Ph)iPr} 2 ] (10). The crystal structures show that the nitrogen atoms of the magnesium-bound N-isopropylanilide ions are in planar environments whereas strontium-bound N-isopropylanilide ions show rather short contacts between the alkaline earth metal and the ipsocarbon atoms of the phenyl groups leading to a pyramidalization of the coordination of the nitrogen atoms.

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Advances in alkaline earth-nitrogen chemistry

Cited by 97 publications

References 171 publications

3-Phenyl-5-(2-pyridyl)pyrazolato Complexes of Lithium, Magnesium, Calcium, and Zinc

3-Phenyl-5-(2-pyridyl)pyrazolato Complexes of Lithium, Magnesium, Calcium, and Zinc

Hydrophosphination of Styrene and Polymerization of Vinylpyridine: A Computational Investigation of Calcium-Catalyzed Reactions and the Role of Fluxional Noncovalent Interactions

Synthesis and Characterization of Strontium Bis(N-isopropylanilide) and Comparison with the Lighter Magnesium and Calcium Congeners

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