Coordination of arenes and phosphines by charge separated alkaline earth cations

Michael Hill, Lucia Garcia, Mathew Anker, Mary Mahon, Laurent Maron

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Generation of β-diketiminato group 2 cations, [(MeBDI)Ae]+ and [(t-BuBDI)Ae]+ (MeBDI = HC{(Me)CN-2,6-iPr2C6H3}2; t-BuBDI = HC{(t-Bu)CN-2,6-i-Pr2C6H3}2; Ae = Mg or Ca), in conjunction with the weakly coordinating
anion, [Al{OC(CF3)3}4] −, allows the characterisation of charge separated alkaline earth η6-π adducts to toluene or benzene when crystallised from the arene solvents. Addition of 1,4-difluorobenzene to [(MeBDI)Mg]+ results in the isolation of [(MeBDI)Mg(1,4-F2C6H4)3]+ in which the fluorobenzene molecules coordinate via κ1
-F–M interactions. Although DFT analysis indicates that the polyhapto arene binding to Mg is effectively electrostatic in origin, the interactions with Ca (Sr and Ba) are observed to invoke small but significant π overlap of the arene HOMOs with the alkaline earth valence nd orbitals.
Reaction of triphenylphosphine with [(MeBDI)Mg]+ and [(t-BuBDI)Mg]+ in toluene solvent allows the isolation
of the respective terminally coordinated magnesium-phosphine adducts. The resultant Mg–P bond
lengths [2.5972(13), 2.6805(12) Å] are comparable to those previously observed in magnesium derivatives
of terminal but formally anionic phosphide ligands, while the effectively electrostatic nature of the
bonding is supported by DFT calculations.
LanguageEnglish
Pages12684-12693
Number of pages10
JournalDalton Transactions
Volume47
Issue number36
Early online date15 Aug 2018
DOIs
StatusPublished - 28 Sep 2018

Cite this

Coordination of arenes and phosphines by charge separated alkaline earth cations. / Hill, Michael; Garcia, Lucia; Anker, Mathew; Mahon, Mary; Maron, Laurent.

In: Dalton Transactions , Vol. 47, No. 36, 28.09.2018, p. 12684-12693.

Research output: Contribution to journalArticle

Hill, Michael ; Garcia, Lucia ; Anker, Mathew ; Mahon, Mary ; Maron, Laurent. / Coordination of arenes and phosphines by charge separated alkaline earth cations. In: Dalton Transactions . 2018 ; Vol. 47, No. 36. pp. 12684-12693.
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abstract = "Generation of β-diketiminato group 2 cations, [(MeBDI)Ae]+ and [(t-BuBDI)Ae]+ (MeBDI = HC{(Me)CN-2,6-iPr2C6H3}2; t-BuBDI = HC{(t-Bu)CN-2,6-i-Pr2C6H3}2; Ae = Mg or Ca), in conjunction with the weakly coordinatinganion, [Al{OC(CF3)3}4] −, allows the characterisation of charge separated alkaline earth η6-π adducts to toluene or benzene when crystallised from the arene solvents. Addition of 1,4-difluorobenzene to [(MeBDI)Mg]+ results in the isolation of [(MeBDI)Mg(1,4-F2C6H4)3]+ in which the fluorobenzene molecules coordinate via κ1-F–M interactions. Although DFT analysis indicates that the polyhapto arene binding to Mg is effectively electrostatic in origin, the interactions with Ca (Sr and Ba) are observed to invoke small but significant π overlap of the arene HOMOs with the alkaline earth valence nd orbitals.Reaction of triphenylphosphine with [(MeBDI)Mg]+ and [(t-BuBDI)Mg]+ in toluene solvent allows the isolationof the respective terminally coordinated magnesium-phosphine adducts. The resultant Mg–P bondlengths [2.5972(13), 2.6805(12) {\AA}] are comparable to those previously observed in magnesium derivativesof terminal but formally anionic phosphide ligands, while the effectively electrostatic nature of thebonding is supported by DFT calculations.",
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N2 - Generation of β-diketiminato group 2 cations, [(MeBDI)Ae]+ and [(t-BuBDI)Ae]+ (MeBDI = HC{(Me)CN-2,6-iPr2C6H3}2; t-BuBDI = HC{(t-Bu)CN-2,6-i-Pr2C6H3}2; Ae = Mg or Ca), in conjunction with the weakly coordinatinganion, [Al{OC(CF3)3}4] −, allows the characterisation of charge separated alkaline earth η6-π adducts to toluene or benzene when crystallised from the arene solvents. Addition of 1,4-difluorobenzene to [(MeBDI)Mg]+ results in the isolation of [(MeBDI)Mg(1,4-F2C6H4)3]+ in which the fluorobenzene molecules coordinate via κ1-F–M interactions. Although DFT analysis indicates that the polyhapto arene binding to Mg is effectively electrostatic in origin, the interactions with Ca (Sr and Ba) are observed to invoke small but significant π overlap of the arene HOMOs with the alkaline earth valence nd orbitals.Reaction of triphenylphosphine with [(MeBDI)Mg]+ and [(t-BuBDI)Mg]+ in toluene solvent allows the isolationof the respective terminally coordinated magnesium-phosphine adducts. The resultant Mg–P bondlengths [2.5972(13), 2.6805(12) Å] are comparable to those previously observed in magnesium derivativesof terminal but formally anionic phosphide ligands, while the effectively electrostatic nature of thebonding is supported by DFT calculations.

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