On the existence of low-valent magnesium–calcium complexes

Mai, Jonathan; Rösch, Bastian; Patel, Neha; Langer, Jens; Harder, Sjoerd

doi:10.1039/d3sc00909b

Cited by 17 publications

(19 citation statements)

References 42 publications

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“…The nacnac ligand framework has subsequently been used by Crimmin to isolate Mg−Zn bonds, while Jones has also reported Mg−Zn bonds in a LZn-Mg(nacnac) com-plex. 52,53 Very recently, the first Mg−Ca bond has been reported, 54 although it could not be isolated due to its high reactivity. Boronski et al 55 have isolated a complex with the first Be−Al bond and more recently the first Be−Be (CpBeBeCp) and Be−Zn (CpBeZn( Dipp nacnac)) bonds.…”

Section: ■ Introductionmentioning

confidence: 99%

“…For alkaline earths, the field started with the seminal breakthrough in 2007 when Jones isolated a low-valent Mg(I) complex of β-diketiminato (nacnac) ligands that exhibited covalent Mg–Mg bonds. − [Mg 2 (nacnac) 2 ] compounds have subsequently become established as versatile reducing reagents. The nacnac ligand framework has subsequently been used by Crimmin to isolate Mg–Zn bonds, while Jones has also reported Mg–Zn bonds in a LZn-Mg(nacnac) complex. , Very recently, the first Mg–Ca bond has been reported, although it could not be isolated due to its high reactivity. Boronski et al have isolated a complex with the first Be–Al bond and more recently the first Be–Be (CpBeBeCp) and Be–Zn (CpBeZn( Dipp nacnac)) bonds .…”

Section: Introductionmentioning

confidence: 99%

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Heteronuclear and Homonuclear Bimetallic Metallocenes of Alkaline Earths and Zinc

Gosch,

Wilson

2023

Organometallics

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Hetero-and homonuclear dimetallocenes of group 2 (alkaline earth) and zinc metals, CpMM′Cp (M = Be, Mg, Ca, Sr, Ba, Zn), have been systematically investigated using quantum chemical calculations with a focus on novel metal−metal bonding, electronic structure, and stability. The metal−metal bonding is generally low-valent covalent bonding between M(I) centers. All BeM complexes along with MgMg, CaCa, CaSr, CaBa, SrSr, and BaBa metallocenes are stable with respect to dissociation, with loss of a neutral metal atom being the most favorable dissociation pathway. As an indicator of electronic stability, the largest highest occupied molecular orbital (HOMO)−lowest unoccupied molecular orbital (LUMO) gaps are calculated for the Be-containing (BeBe, BeZn, BeMg; 3.17−5.95 eV) and MgMg (4.84 eV) metallocenes. Remarkably, CpBeBeCp with the first Be−Be bond has just been isolated [Science 2023[Science , 380, 1147[Science −1149, with CpBeZnNacnac representing the first Be−Zn bond. The BeZn and BeMg metallocenes are promising targets for isolation, which would represent the first isolated Be−Mg covalent bond. Quantum theory of atoms in molecule (QTAIM) calculations highlight novel metal−metal bonding with BeBe, MgMg, CaCa, and SrSr metallocenes, with a non-nuclear local maximum in their electron density, termed a "non-nuclear attractor" (NNA) or "pseudoatom". CpBeBeCp is unique in potentially having two NNAs in the Be− Be bond that contains 1.4 electrons that are delocalized and weakly bound. The metal−metal bonds are not just a simple bond with one bond critical point but rather by a bond exhibiting the more complex feature of two (or more) bond critical points mediated by pseudoatoms. The implications for bonding and reducing the reactivity of CpBeBeCp are discussed.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heteronuclear and Homonuclear Bimetallic Metallocenes of Alkaline Earths and Zinc

Gosch,

Wilson

2023

Organometallics

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“…Its 9 Be and 31 P NMR shifts at 24.3 and −53.5 ppm, respectively, are comparable to those of the similarly coordinated [(Me 3 P)Be(nBu) 2 ] (δ 9Be = 23.3 ppm, δ 31P = −60.9 ppm). 54 Subsequent insertion of the beryllium center into the N1−C1 bond and migration of the PMe 3 ligand to C1 yields the zwitterionic beryllacycle 5, which displays a similar six-membered C 4 BeN ring and 9 Be NMR shift (δ 9Be = 16.8 ppm) to 3 (δ 9Be = 17.4 ppm). Its 31 P NMR resonance at 17.3 ppm is 70 ppm downfield-shifted from 4 and slightly downfield-shifted from that of [PMe 4 ]Cl (δ 31P = 26 ppm), confirming its nature as a tetraalkylphosphonium.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Tricoordinate Beryllium Radicals and Their Reactivity

Czernetzki,

Arrowsmith,

Endres

et al. 2024

Inorg. Chem.

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The one-electron reduction of [(CAAC)Be(Dur)Br] (CAAC = cyclic alkyl(amino)carbene, Dur = 2,3,5,6tetramethylphenyl = duryl) with lithium sand in diethyl ether yields the first neutral, tricoordinate, and moderately stable beryllium radical, [(CAAC)(Et 2 O)BeDur] • (2-Et 2 O), which undergoes a facile second one-electron reduction concomitant with the insertion of the beryllium center into the endocyclic C−N CAAC bond and a cyclopropane-forming C−H bond activation of an adjacent methyl group. In situ generation of 2-Et 2 O and addition of PMe 3 yield the stable analogue, [(CAAC)(Me 3 P)BeDur] • (2-PMe 3 ), which serves as a platform for PMe 3 -ligand exchange with stronger donors, generating the radicals [(CAAC)LBeDur] • (2-L, L = isocyanides, pyridines, and N-heterocyclic carbenes). X-ray structural analyses show trigonal-planar beryllium centers and strong π backbonding from the metal to the CAAC ligand. The EPR signals of all six isolated [(CAAC)LBeDur]• radicals display significant, albeit small, hyperfine coupling to the 9 Be nucleus. DFT calculations show that the spin density is mostly delocalized over the CAAC π framework and, where present, the isocyanide CN moiety, with only a small proportion (3−6%) on the beryllium center. 2-PMe 3 proved thermally unstable at 80 °C, first undergoing radical hydrogen abstraction with the solvent, followed by insertion of beryllium into the endocyclic C−N CAAC bond and PMe 3 transfer to the former carbene carbon atom. The reactions with diphenyl disulfide and phenyl azide occur at the beryllium center and yield the corresponding Be(II) phenyl sulfide and amino complexes, respectively, the latter concomitant with radical transfer and hydrogen abstraction by the beryllium-bound nitrogen center.

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“…Moreover, compounds of the Mg (0) type as well as low-valent magnesium-calcium complexes will be the object of future theoretical investigations since these systems with BDI seem to be able to activate inert molecules. 60,61…”

Section: Papermentioning

confidence: 99%

Activation of the N₂ molecule by means of low-valence complexes of calcium and magnesium

et al. 2023

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On the existence of low-valent magnesium–calcium complexes

Abstract: DFT-Calculations predict that a low-valent complex (BDI)Mg-Ca(BDI) with bulky b-diketiminate (BDI) ligands is thermodynamically stable. It was attempted to isolate such a complex by salt-metathesis between [(DIPePBDI*)MgˉNa+]2 and [(DIPePBDI)CaI]2 (DIPePBDI...

Cited by 17 publications

References 42 publications

Heteronuclear and Homonuclear Bimetallic Metallocenes of Alkaline Earths and Zinc

Heteronuclear and Homonuclear Bimetallic Metallocenes of Alkaline Earths and Zinc

Tricoordinate Beryllium Radicals and Their Reactivity

Activation of the N₂ molecule by means of low-valence complexes of calcium and magnesium

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On the existence of low-valent magnesium–calcium complexes

Abstract: DFT-Calculations predict that a low-valent complex (BDI)Mg-Ca(BDI) with bulky b-diketiminate (BDI) ligands is thermodynamically stable. It was attempted to isolate such a complex by salt-metathesis between [(DIPePBDI*)MgˉNa+]2 and [(DIPePBDI)CaI]2 (DIPePBDI...

Cited by 17 publications

References 42 publications

Heteronuclear and Homonuclear Bimetallic Metallocenes of Alkaline Earths and Zinc

Heteronuclear and Homonuclear Bimetallic Metallocenes of Alkaline Earths and Zinc

Tricoordinate Beryllium Radicals and Their Reactivity

Activation of the N2 molecule by means of low-valence complexes of calcium and magnesium

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Activation of the N₂ molecule by means of low-valence complexes of calcium and magnesium