Reactivity of zinc hexazene complexes

Reactivity of zinc hexazene complexes

(MesnacnacZn)2(μ-η22-N6Ph2) containing the sterically less demanding Ph-substituent is a powerful hexazene transfer reagent in reactions with transition metal and main group metal complexes. Reactions of (MesnacnacZn)2(μ-η22-N6Ph2) with equimolar amounts of Me2Zn, Me3Al and MeLi occurred with elimination of MesnacnacZnMe and subsequent formation of the heteroleptic and heterobimetallic hexazene complexes (Scheme 10).

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Scheme 10: Reactions of (MesnacnacZn)2(μ-η22-N6Ph2) with one equivalent ZnMe2, AlMe3 and MeLi.

The reaction of (MesnacnacZn)2(μ-η22-N6Ph2) with 2 eq ZnMe2 leads under MesnacnacZnMe elimination to the new hexazene complex (MeZn)2(μ-η22-N6Ph2).[21] Intermolecular Zn∙∙∙N interactions result in the formation of ladder-like one-dimensional polymeric structure (Figure 7).

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Figure 7: Molecular structure of (MeZn)2(μ-η22-N6Ph2) and intermolecular interactions.

The intermolecular Zn∙∙∙N interactions can be disrupted in reactions with stronger Lewis bases such as acetonitrile or pyridine, resulting in the formation of the Lewis base-coordinated hexazene complexes (MeZn)2(μ-η22-PhN6Ph)(CH3CN)2 and (MeZn)2(μ-η22-PhN6Ph)(C5H5N)2 (Figure 8).

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Figure 8: Molecular structures of (MeZn)2(μ-η22-N6Ph2)(CH3CN)2 (left) and (MeZn)2(μ-η22-N6Ph2)(C5H5N)2 (right).

(MeZn)2(μ-η22-N6Ph2) also reacts with H-acidic ligands such as HC(C(Me)NPh)2 with CH4 elimination, yielding the new hexazene complex (PhnacnacZn)2(μ-η22-N6Ph2) (Figure 9).

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Figure 9: Molecular structure of (PhnacnacZn)2(μ-η22-N6Ph2).

Reactions with elemental chalcogenes and Diphenyl-Dichalcogenides

Reactions of Zn(I) complexes with elemental chalcogenes E or chalcogenophosphoranes Bu3P=E (E = Se, Te) failed to give the expected insertion products. Reactions of Mesnacnac2Zn2 with elemental sulfur occurred with oxidation of the γ-carbon atom and formation of ZnS and [MesnacnacS]2Zn (Figure 10).[22] This reactivity of nacnac ligands is also known in the chemistry of Cu(I) complexes.[23]

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Figure 10: Molecular structure of (MesnacnacS)2Zn.

In contrast, reactions of Mesnacnac2Zn2 with one equivalent of Ph2E2 (E= S, Se, Te) yielded the zinc chalcogenide dimers [MesnacnacZnEPh]2, which can be furhter oxidized in reactions with O2 to the corresponding metalated chalcogenic acids [MesnacnacZnEPhO2]2 (Figure 11).[24]

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Figure 11: Molecular structure of [MesnacnacZn-SePh]2 and the metalated selenic and tellurinic acid.

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