The First Structurally Characterized Homoleptic Aryl-Manganese(III) Compound and the Corresponding Isoleptic and Isoelectronic Chromium(II) Derivative

Forniés, Juan; Martín, António; Martín, and L. Francisco; Menjón, Babil; Zhen, Hongshi; Bell, and Andrew; Rhodes, Larry F.

doi:10.1021/om050206e

Cited by 23 publications

(9 citation statements)

References 42 publications

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“…3) where the cation is formed by an octahedral magnesium surrounded by six molecules of THF whereas the anionic moiety consists of two zinc atoms bonded to two chlorine bridges and two terminal ones in a distorted tetrahedral geometry. Several examples of other mixed-metal compounds containing either one of these two ions, separately but never together, have been reported (23)(24)(25)(26). However, surprisingly a search of the Cambridge Crystallographic Database revealed that the 1∶2, Mg∶Zn stoichiometry found in compound 3 is extremely rare across the whole of mixed magnesium-zinc chemistry, with only three such compounds structurally characterized to date (27)(28)(29).…”

Section: Resultsmentioning

confidence: 99%

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids

Hevia

Chua

García‐Álvarez

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Studying seemingly simple metathesis reactions between ZnCl 2 and t BuMgCl has, surprisingly, revealed a much more complex chemistry involving mixed magnesium-zinc compounds that could be regarded as Mg-Zn hybrids. Thus, the reaction of equimolar amounts of ZnCl 2 and t BuMgCl reveals the formation of the unprecedented mixed Mg-Zn complex [ðTHFÞ 4 Mgðμ-ClÞ 2 Znð t BuÞðClÞ] (1), as a result of the co-complexation of the two anticipated exchange products of the metathesis. This magnesium zincate adopts a contacted ion-pair structure, closely related to Knochel's pioneering "Turbo" Grignard reagents. Furthermore, a second coproduct identified in this reaction is the solvent-separated mixed magnesiumzinc chloride complex [fMgðTHFÞ 6 g 2þ fZn 2 Cl 6 g 2− ] (3) that critically diminishes the amount of ZnCl 2 available for the intended metathesis reaction to take place. In another surprising result, when the reaction is carried out by using an excess of 3 M equivalents of the Grignard reagent (closer to the catalytic conditions employed by synthetic chemists), solvent-separated magnesium trialkyl zincate [fMg 2 Cl 3 ðTHFÞ 6 g þ fZnð t BuÞ 3 g − ] (4) is obtained that can be viewed as a model for the active species involved in the increasingly important organic transformations of Grignard reagents catalysed by ZnCl 2 . Furthermore, preliminary reactivity studies reveal that complex 4 can be used as an effective new reagent for direct Zn-I exchange reactions that allow the preparation and structural identification of the magnesium tris(aryl) zincate [fMg 2 Cl 3 ðTHFÞ 6 g þ fZnðp-TolÞ 3 g − ] (5) that represents the first example of complete 3-fold activation of a zincate in a Zn-I exchange reaction which, in turn, can efficiently be used as a precursor for Negishi crosscoupling reactions.

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Section: Resultsmentioning

confidence: 99%

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids

Hevia

Chua

García‐Álvarez

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…However, by reacting MnBr 2 with the Grignard reagent Mg(C 6 F 5 )Br, compound [Mg(thf) 6 ]-[Mn III (C 6 F 5 ) 4 ] 2 was obtained as a result of a combined arylation and oxidation process (Scheme 2). 31 In contrast with the behaviour observed for Mn, the reaction of FeCl…”

Section: Magnetic Propertiesmentioning

confidence: 80%

“…While the C 6 F 5 rings are almost perpendicular to the metal coordination plane in [Cr II (C 6 F 5 ) 4 ] 2− (Fig. 9), 31 the C 6 Cl 5 rings in [Cr II (C 6 Cl 5 ) 4 ] 2− adopt a helical arrangement around the normal to that plane (Fig. 10), 28 again introducing a source of chirality.…”

Section: Configuration Would Be Expected (See Below)mentioning

confidence: 99%

New advances in homoleptic organotransition-metal compounds: The case of perhalophenyl ligands

et al. 2007

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Homoleptic derivatives of formula [M(C(6)X(5))(n)](z-) (X = F, Cl) have been prepared and isolated for every first-row transition metal as well as for several of the heavier ones. The stoichiometry attained in each case (n ranging between 2 and 6) can be understood considering the tendency of a given metal ion to compensate its coordinative and electronic unsaturation, while not incurring severe interligand repulsive effects. The molecular structures associated with each stoichiometry seem, in turn, to be governed by electronic rather than steric factors. Most of these [M(C(6)X(5))(n)](z-) compounds are unsaturated, open-shell organometallic species, not fulfilling the 18-electron (or Effective Atomic Number) rule. This behaviour can be attributed to the absence of pi stabilising ligands (such as CO, phosphines, alkenes, alkynes, a variety of substituted aromatic rings, and so on) which are otherwise ubiquitous in organotransition-metal chemistry. The magnetic properties of the [M(C(6)X(5))(n)](z-) species have been determined by EPR spectroscopy and/or bulk magnetisation measurements. Excellent correlation between molecular geometry and magnetic properties (whether diamagnetic or paramagnetic) has been observed. Many of these compounds undergo chemically- or electrochemically-induced electron exchange processes. These redox reactions proceed without alteration in the stoichiometry of the [M(C(6)X(5))(n)](z-) compound, but usually involve a sharp change in the molecular geometry according to the different electron configuration of the interrelated species.

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“…7 Similar Cr-C bond distances (average Cr-C = 215.8(6) pm) were also found in the homoleptic square-planar (SP-4) organochromium(II) derivative [Mg(thf) 6 ][Cr II (C 6 F 5 ) 4 ]•2thf, regardless of the different oxidation state of the metal centre. 12 It is reasonable to assume that the change in coordination number would compensate for the decrease in the Cr-C distance expected to occur on going from Cr II to Cr III . The C 6 F 5 groups in 2 and 3 adopt a heavily tilted disposition with respect to the equatorial plane (tilt angles: 44.0-55.8 • ), while in the aforementioned homoleptic Cr II derivative they were found to be roughly perpendicular to the coordination plane (tilt angles: 74.8-88.8 • ).…”

Section: Synthesis and Structural Characterisationmentioning

confidence: 99%

Synthesis, characterisation and magnetic properties of octahedral chromium(iii) compounds with six C-donor ligands

et al. 2011

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The homoleptic, square pyramidal organochromium(III) compound [NBu(4)](2)[Cr(C(6)F(5))(5)] (1) reacts with excess organic isocyanides, CNR [R = (t)Bu, 2,6-dimethylphenyl (Xy)], under dissociation of the apical C(6)F(5) ligand to give the more saturated, singly charged complexes [NBu(4)][trans-Cr(C(6)F(5))(4)(CNR)(2)] [R = (t)Bu (2), Xy (3)], containing six monodentate C-donor ligands. These compounds exhibit an axially distorted octahedral structure (single-crystal X-ray diffraction) with the four C(6)F(5) groups defining the equatorial positions and the CNR ligands occupying the axial ones. Compounds 2 and 3 both behave as spin quartet species (S = 3/2) at microscopic level (EPR spectroscopy), their macroscopic magnetic properties depending upon the nature of the terminal R group, as established by magnetisation measurements. When the R substituent is the saturated alkyl group (t)Bu, the compound (2) behaves as a simple paramagnet, with no magnetic interaction between individual Cr(III) centres along the whole temperature range measured (1.8-265 K). By contrast, a weak antiferromagnetic interaction is detected for compound 3 at low temperature with T(N) = 0.19(1) K. Since the closest intermetallic distances are similar in the crystals of 2·CH(2)Cl(2) and 3·1.75CH(2)Cl(2) (ca. 1.1 nm), we conclude that the insaturation of the aromatic Xy group together with the extended intermolecular π-π stacking interactions between Xy rings observed in the crystal lattice of 3·1.75CH(2)Cl(2) (centroid-to-centroid distance: 0.35 nm) favour magnetic interaction between the individual magnetic centres.

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The First Structurally Characterized Homoleptic Aryl-Manganese(III) Compound and the Corresponding Isoleptic and Isoelectronic Chromium(II) Derivative

Cited by 23 publications

References 42 publications

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids

New advances in homoleptic organotransition-metal compounds: The case of perhalophenyl ligands

Synthesis, characterisation and magnetic properties of octahedral chromium(iii) compounds with six C-donor ligands

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