| Abstract
| - Reaction of (Me3SiNPPh2)2CH2 with Ba[N(SiMe3)2]2 in 1:1 ratio gave only monodeprotonation andthe homoleptic product [(Me3SiNPPh2)2CH]2Ba (3-Ba) was formed. Reaction with the strong basedibenzylbarium gave fast and clean 2-fold deprotonation and the dimeric complex [(Me3SiNPPh2)2CBa·THF]2 (1-Ba) was isolated. Also the bulkier ligand (2,6-iPr2C6H3−NPPh2)2CH2 was doublydeprotonated by this reagent, which gave clean formation of the monomeric complex (2,6-iPr2C6H3−NPPh2)2CBa·(THF)3 (2-Ba). Although organobarium compounds generally show high reactivity, themonomeric barium carbene complex 2-Ba reacted sluggishly with benzophenone or adamantyl cyanideand reaction products could not be identified. Reaction of 2-Ba with cyclohexyl isocyanate, however,cleanly gave the [2+2]-cycloaddition product, which crystallized as a dimer (4). Crystal structures ofmonomers 2-Ba and 3-Ba and dimers 1-Ba and 4 show in all cases tridentate (C, N, N‘)-coordination ofthe bis-iminophosphorano ligand. In some cases the large coordination sphere of Ba2+ was saturated byagostic iPr···Ba2+ and π-Ph···Ba contacts.
- Dimeric and monomeric barium carbene complexes with chelating bis-iminophosphorano substituents were obtained by 2-fold deprotonation of (RNPPh2)2CH2 ligands with dibenzylbarium. These barium carbene complexes react sluggishly with benzophenone and adamantyl cyanide, but reaction with an isocyanate gave clean [2+2]-cycloaddition.
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