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. 2025 Mar 3;44(6):737-748.
doi: 10.1021/acs.organomet.4c00504. eCollection 2025 Mar 24.

Exploring the Nuclearity and Structural Motifs of Phenoxyimine Alkaline Earth Complexes

Amy V Rizzo  1 , Rebecca L Jones  1 , Matthew D Haynes  1 , Clement G Collins Rice  1 , Jean-Charles Buffet  1 , Zoë R Turner  1 , Dermot O'Hare  1
Affiliations

Exploring the Nuclearity and Structural Motifs of Phenoxyimine Alkaline Earth Complexes

Amy V Rizzo et al. Organometallics. .

Abstract

The nuclearity and structural motifs of alkaline earth complexes supported by bidentate phenoxyimine ligands has been explored by modulation of the stereoelectronic profile of the ligand, the atomic number of the metal, and the synthetic protocol. Changing the size of the N-imine substituents was found to have no effect on protonolysis reactions between [MgN″2]2 or CaN″2(thf)2 (N″ = N(SiMe3)2) and H t Bu2,ArL (1-OH-2-CH = NAr-4,6- t Bu-C6H2; Ar = 2,6-iPr-C6H3 = Dipp or 2,6-CHPh2-4-Me-C6H2 = Ar*) regardless of reaction stoichiometry, with homoleptic bis(ligand) complexes ( t Bu2,DippL)2Mg (1), ( t Bu2,Ar*L)2Mg (2), ( t Bu2,DippL)2Ca(thf) (3) and ( t Bu2,Ar*L)2Ca(thf) (4) isolated. The importance of reaction protocol was demonstrated by the facile isolation of heteroleptic complex ( t Bu2,Ar*L)MgI(OEt2) (5) from the reaction of equimolar amounts of H t Bu2,Ar*L and MeMgI. Importantly, no subsequent ligand redistribution was observed when complex 5 readily reacted with KN" or KODipp to form ( t Bu2,Ar*L)Mg{N(SiMe3)2}(OEt2) (6) and ( t Bu2,Ar*L)Mg(ODipp)(thf) (7). When small 4,6-phenoxide substituents were considered (HH2,DippL), multimetallic clusters were afforded: (H2,DippL)3Ca2(N″)(thf) (8) and (H2,DippL)6Sr3 (9).

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Chart 1
Chart 1. Strategies for Isolating M2+ Heteroleptic Schiff-Base Complexes Exemplified by (a) Mecking and Co-Workers, (b) Ma and Co-Workers, and (c) Darensbourg and Co-Workers; (d) Phenoxyimine NOON and (e) NON Alkaline Earth Complexes Reported by Jones et al., and (f) This Work.
Scheme 1
Scheme 1. Protonolysis Reactions between HtBu2,ArL and MN″2(thf)2 (M = Mg and Ca) Affording (tBu2,DippL)2Mg (1), (tBu2,Ar*L)2Mg (2), (tBu2,DippL)2Ca(thf) (3) and (tBu2,Ar*L)2Ca(thf) (4)
Relative ligand orientations depicted consistent with solid-state structural data.
Figure 1
Figure 1
Thermal displacement ellipsoid drawings (30% probability) of (tBu2,DippL)2Mg (1), (tBu2,Ar*L)2Mg (2), (tBu2,DippL)2Ca(thf) (3) and (tBu2,Ar*L)2Ca(thf) (4). All hydrogen atoms and solvent of recrystallization are omitted for clarity.
Scheme 2
Scheme 2. Protonolysis Reactions between HtBu2,Ar*L and MeMgI Affording (tBu2,Ar*L)MgI(OEt2) (5), and Subsequent Salt Metathesis Reactions with KX to Form (tBu2,Ar*L)MgN″(OEt2) (6) and (tBu2,Ar*L)Mg(ODipp)(thf) (7)
Figure 2
Figure 2
Thermal displacement ellipsoid drawings (30% probability) of (tBu2,Ar*L)Mg(N″)(thf), (tBu2,Ar*L)Mg(ODipp)(thf) (7). All hydrogen atoms have been omitted for clarity.
Figure 3
Figure 3
Thermal displacement ellipsoid drawings (30% probability) of (H2,DippL)3Ca2N″(thf) (8) and (H2,DippL)6Sr3 (9). All hydrogen atoms have been omitted and each ligand in complex 10 has been color-coded for additional clarity.
Scheme 3
Scheme 3. Protonolysis Reactions between HDippL and MN″2(thf)2 (M = Ca and Sr) to Afford Clusters (a) (H2,DippL)3Ca2(N″)(thf) (8) and (b) Sr3(H2,DippL)6 (9)
See this image and copyright information in PMC

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