Magnesium compounds: Classification and analysis of crystallographic and structural data

Holloway, Clive Ε.; Melnı́k, Milan

doi:10.1016/0022-328x(94)87036-5

Cited by 80 publications

(56 citation statements)

References 328 publications

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“…The umpolung at this carbon via substitution of bromine by magnesium leads to narrower angles at the ipso-carbon atoms in complex 2 (C2-C1-C6 115.8 (2) • and C34-C33-C38 115.6(2) • ) due to electrostatic repulsion between the negatively charged electron pair and the neighboring bonds to the ortho-carbon atoms. The Mg1-C bond lengths of 219.3(3) and 218.3(3) pm lie in the expected range as also observed for other organomagnesium complexes [20][21][22][23][24]. The magnesium atom is rather small for the bite of the anionic ligand.…”

Section: Reduction Of Bromo-26-bis(diphosphanylmethyl)benzene With Msupporting

confidence: 79%

Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium

et al. 2016

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Arylmagnesium and -calcium reagents are easily accessible; however, ether degradation processes limit storability, especially of the calcium-based heavy Grignard reagents. Ortho-bound substituents with phosphanyl donor sites usually block available coordination sites and stabilize such complexes. The reaction of bromo-2,6-bis(diphenylphosphanylmethyl)benzene (1a) with magnesium in tetrahydrofuran yields [Mg{C 6 H 3 -2,6-(CH 2 PPh 2 ) 2 } 2 ] (2) after recrystallization from 1,2-dimethoxyethane. However, the similarly performed reduction of bromo-(1a) and iodo-2,6-bis(diphenylphosphanylmethyl)benzene (1b) with calcium leads to ether cleavage and subsequent degradation products. α-Deprotonation of tetrahydrofuran (THF) yields 1,3-bis(diphenylphosphanylmethyl)benzene. Furthermore, the insoluble THF adducts of dimeric calcium diphenylphosphinate halides, [(thf) 3 Ca(X)(µ-O 2 PPh 2 )] 2 [X = Br (3a), I (3b)], precipitate verifying ether decomposition and cleavage of P-C bonds. Ether adducts of calcium halides (such as [(dme) 2 (thf)CaBr 2 ] (4)) form, supporting the initial Grignard reaction and a subsequent Schlenk-type dismutation reaction.

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Section: Reduction Of Bromo-26-bis(diphosphanylmethyl)benzene With Msupporting

confidence: 79%

Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium

et al. 2016

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“…[42,43,59,60] Further parameters derived from the calculations are given in Tables S3 and S4 in the Supporting Information.…”

Section: Mementioning

confidence: 99%

“…[60] Although much less common, linear two-coordinate MgR 2 (R = alkyl, aryl) have also been structurally characterised for sterically demanding R groups. [43,61] It was therefore of interest to compare the relative energies of the k Figure 7; selected bond lengths and angles are compiled in Table 3. Although C-coordinated isomers featuring one k…”

Section: Màme Bond Orbital a C H T U N G T R E N N U N G (Homoà1)mentioning

confidence: 99%

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Syntheses, Reactivity and DFT Studies of Group 2 and Group 12 Metal Complexes of Tris(pyrazolyl)methanides Featuring “Free” Pyramidal Carbanions

Bigmore

Meyer

Krummenacher

et al. 2008

Chemistry A European J

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Reactions of HC(Me2pz)3 with Grignard reagents, dialkyl magnesium compounds and dimethylzinc are reported, together with a DFT study on some of the aspects of this chemistry. Reactions of HC(Me2pz)3 with MeMgX (X=Cl or Br) gave the half-sandwich zwitterionic compounds [Mg((Me)Tpmd)X] (X=Cl (2) or Br (3); (Me)Tpmd(-)=[C(Me2pz)3](-)). Addition of HCl to 2 gave the structurally characterised half-sandwich compound [Mg{HC(Me2pz)3}Cl2(thf)] (4). The zwitterionic sandwich compound [Mg(MeTpmd)2] (5) formed in low yields in the reaction of MeMgX with HC(Me2pz)3 but was readily prepared from HC(Me2pz)3 and either MgnBu2 or MgPh2. The structurally characterised compound 5 contains two "naked" sp3-hybridised carbanions fully separated from the dicationic metal centre. Only by using MgPh2 as starting material could the half-sandwich compound [Mg(MeTpmd)Ph(thf)] (6) be isolated. The zwitterionic sandwich compound 5 reacted with HOTf (OTf(-)=[O3SCF3](-)) to form the dication [Mg{HC(Me2pz)3}2]2+ (7(2+)), which was structurally characterised. Pulsed field gradient spin-echo (PGSE) diffusion NMR spectroscopy revealed both compounds to be intact in solution. In contrast to the magnesium counterparts, HC(Me2pz)3 reacted only slowly with ZnMe2 (and not at all with ZnPh2) to form the half-sandwich zwitterion [Zn(MeTpmd)Me] (8), which contains a cationic methylzinc moiety separated from a single sp3-hybridised carbanion. Density functional calculations on the zwitterions [M(MeTpmd)Me] and [M(MeTpmd)2] (M=Mg, Zn) revealed that the HOMO in each case is a (Me)Tpmd-based carbanion lone pair. The kappa 1C isomers of [M(MeTpmd)Me] were calculated to be considerably less stable than their kappa 3N-bound counterparts, with the largest gain in energy for Mg due to the greater ease of electron transfer from metal to the (Me)Tpmd apical carbon atom on formation of the zwitterion. Moreover, the computed M-C bond dissociation enthalpies of the kappa 1C isomers of [M(MeTpmd)Me] are considerably higher than expected by simple extrapolation from the corresponding computed H-C bond dissociation enthalpy.

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“…The crystallinity of the compound was checked by powder X-ray diffraction (Bruker diffractometer, Cu-Kα 1 radiation), which confirmed the orthorhombic structure previously reported in the literature. [28,29] NMR measurements were conducted at room temperature using a 600 MHz Bruker Avance-II + spectrometer, at a frequency of 36.74 MHz for 25 Mg (158.73 MHz for 23 Na). All spectra were externally referenced to 11 M MgCl 2 aqueous solution in the case of 25 Mg and to 0.1 M NaCl aqueous solution for 23 Na.…”

Section: Methodsmentioning

confidence: 99%

Solid‐state natural abundance ²⁵Mg NMR studies of Na₂MgEDTA·4H₂O—a possible new reference compound for ²⁵Mg NMR spectroscopy

Freitas

Wong

Smith

2008

Magnetic Reson in Chemistry

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Natural abundance solid-state (25)Mg NMR measurements were made of the disodium salt of magnesium ethylenediaminetetraacetate tetrahydrate (Na(2)MgEDTA x 4 H(2)O). Both magic angle spinning (MAS) and static experiments were employed to determine the quadrupole coupling constant (C(q)) and the asymmetry parameter (eta(q)) of the electric field gradient (EFG) tensor associated with (25)Mg in this compound, giving the values C(q) = 1.675(5) MHz and eta(q) = 0.15(1). The isotropic chemical shift was determined to be delta(iso) = 0.25(10) ppm (relative to 11 M MgCl(2) aqueous solution) and a small chemical shift anisotropy (CSA) contribution (approximately -13 ppm) was detected, one of the first CSA reports in (25)Mg NMR. This compound exhibited remarkably good (25)Mg NMR sensitivity, due to its fast spin-lattice relaxation and modest quadrupole coupling, which allowed its use as a secondary shift reference and as a test sample for the implementation and optimisation of signal-enhancement methods in (25)Mg NMR spectroscopy, such as double frequency sweeps (DFS) and the use of adiabatic hyperbolic secant (HS) and WURST pulses.

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Magnesium compounds: Classification and analysis of crystallographic and structural data

Cited by 80 publications

References 328 publications

Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium

Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium

Syntheses, Reactivity and DFT Studies of Group 2 and Group 12 Metal Complexes of Tris(pyrazolyl)methanides Featuring “Free” Pyramidal Carbanions

Solid‐state natural abundance ²⁵Mg NMR studies of Na₂MgEDTA·4H₂O—a possible new reference compound for ²⁵Mg NMR spectroscopy

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Magnesium compounds: Classification and analysis of crystallographic and structural data

Cited by 80 publications

References 328 publications

Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium

Reduction of Bromo- and Iodo-2,6-bis(diphenylphosphanylmethyl)benzene with Magnesium and Calcium

Syntheses, Reactivity and DFT Studies of Group 2 and Group 12 Metal Complexes of Tris(pyrazolyl)methanides Featuring “Free” Pyramidal Carbanions

Solid‐state natural abundance 25Mg NMR studies of Na2MgEDTA·4H2O—a possible new reference compound for 25Mg NMR spectroscopy

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Solid‐state natural abundance ²⁵Mg NMR studies of Na₂MgEDTA·4H₂O—a possible new reference compound for ²⁵Mg NMR spectroscopy