Low coordinate magnesium chemistry supported by a bulky β-diketiminate ligand

Dove, Andrew P.; Gibson, Vernon C.; Hormnirun, Pimpa; Marshall, Edward L.; Segal, John A.; White, Andrew J. P.; Williams, David J.

doi:10.1039/b303550f

Cited by 116 publications

(86 citation statements)

References 30 publications

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“…Thus, reaction of two equivalents of HCA C H T U N G T R E N N U N G (Me 2 pz) 3 (6) only forms in low yields, and considerable amounts of 5 must be separated by fractional crystallisation. [35] Even though the crystallisation procedure was repeated several times, the isolated portions of 6 all contained impurities of MgPh 2 . The latter had to be used in excess in order to suppress formation of sandwich complex 5.…”

Section: Resultsmentioning

confidence: 99%

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

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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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Section: Resultsmentioning

confidence: 99%

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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“…For magnesium, use of the HN( i Pr) 2 ligand leads to [(BDI)Mg{N( i Pr) 2 }(thf)] [113], or the donor free [(BDI)Mg{N( i Pr) 2 }] monomers [123]. For calcium, use of HN(Ph) 2 results in a monomeric species, [(BDI)Ca{N(Ph) 2 }(thf)] displaying Ca· · ·C() from one of the phenyl groups of the amido ligand [124].…”

Section: Heteroleptic Amidesmentioning

confidence: 99%

Advances in alkaline earth-nitrogen chemistry

Torvisco

O'Brien

Ruhlandt‐Senge

2011

Coordination Chemistry Reviews

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“…Here we were able to grow crystals and have shown that this forms a 3-coordinate structure which is quite different from the dimeric structure of [BDIMg n Bu] 2 [7] but more closely related to the structure of BDIMgPh [8] which too was a monomer.…”

Section: Synthesismentioning

confidence: 84%

“…We have now considered what happens when neat THF is added to the solution in toluene d 8 . When one equivalent of neat THF is added we observed above 60°C one signal for the a-CH 2 THF signals as the free and coordinated THF are exchanging but below À70°C we see the freezing out of the THF exchange.…”

Section: H Nmr Studiesmentioning

confidence: 99%

BDI∗MgX(L) where X = Bu and O Bu and L = THF, py and DMAP. The rates of kinetic exchange of L where BDI∗= CH{C( Bu)N-2,6- Pr2C6H3}2

et al. 2016

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a b s t r a c t BDI * Mg n Bu(THF) and rac-LA to produce heterotactic PLA have been shown to increase from P r = 0.5-0.65 from DCM to neat THF. The increase in concentration of THF from M THF = 0 in toluene to neat THF is shown to occur by THF dissociation as deduced by 1 H NMR studies. In related systems where X = n Bu and O t Bu and with ligands L = THF, py and DMAP similar processes occur by which external exchange of L occurs with added free ligand. For X = n Bu and L = THF, the activation parameters for the dissociation process are DH ╪ = 7.0 ± 0.5 kcal mol À1 and DS ╪ = À11.6 ± 0.4 cal mol À1 and for X = O t Bu and L = THF are DH ╪ = 11.1 ± 1.0 kcal mol À1 and DS ╪ = À3.3 ± 3.9 cal mol À1 . The BDI * (R = t Bu) is notably larger than BDI (R = Me) and this limits the use of THF to coordinate during catalysis. The three coordinate complex BDI * Mg n Bu has been structurally characterized by single crystal X-ray crystallography: where Mg-N = 2.010(4) and 2.026(4) Å and Mg-C = 2.117(5) Å, with N-Mg-N = 94.2(2)°and N-Mg-C = 130.0(2)°and 135.8(2)°. The related complexes BDI * Mg n Bu(L), where L = py and DMAP have similar structural features.

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Low coordinate magnesium chemistry supported by a bulky β-diketiminate ligand

Cited by 116 publications

References 30 publications

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

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

Advances in alkaline earth-nitrogen chemistry

BDI∗MgX(L) where X = Bu and O Bu and L = THF, py and DMAP. The rates of kinetic exchange of L where BDI∗= CH{C( Bu)N-2,6- Pr2C6H3}2

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