Lanthanum and alkali metal coordination chemistry of the bis(dimethylphenylsilyl)amide ligand

The coordination chemistry of the bis(dimethylphenylsilyl)amide ligand, [N(SiMe2Ph)(2)](1-), with sodium, potassium, and lanthanum has been investigated for comparison with the more commonly used [N(SiMe3)(2)](1-) and [N(SiHMe2)(2)](1-) ligands. HN(SiMe2Ph)(2) reacts with KH to produce KN(SiMe2Ph)(2), 1, which crystallizes from toluene as the dimer [KN(SiMe2Ph)(2)(C7H8)](2), 2. The structure of 2 shows that the [N(SiMe2Ph)(2)](1-) ligand can function as a polyhapto ligand with coordination from each phenyl group as well as the normal nitrogen ligation and agostic methyl interactions common in methylsilylamides. Each potassium in 2 is ligated by an eta(4)-toluene, two bridging nitrogen atoms, and an eta(2)-phenyl, an eta(1)-phenyl, and an eta(1)-methyl group. KN(SiMe2Ph)(2) crystallizes from toluene in the presence of 18-crown-6 to make the monometallic complex (18-crown-6)KN(SiMe2Ph)(2), 3, in which [N(SiMe2Ph)(2)](1-) functions as a simple monodentate ligand through nitrogen. The reaction of HN(SiMe2Ph)(2) with NaH in THF at reflux for 2 days generates Na[N(SiMe2Ph)(2)], 4, which crystallizes as the solvated dimer {(THF)Na[mu-eta(1):eta(1)-N(SiMe2Ph)(2)]}(2), 5. A lanthanide metallocene derivative of [N(SiMe2Ph)(2)](1-) was obtained by reaction of K(N(SiMe2Ph)(2)] with [(c(5)Me(5))(2)La][(u-Ph)(2)BPh2]. Crystals of (C5Me5)(2)La[N(SiMe2Ph)(2)], 6, show agostic interactions between lanthanum and methyl groups of each silyl substituent. The [N(SiMe3)(2)](1-) analogue of 3, (18-crown-6)KN(SiMe3)(2), 7, was also structurally characterized for comparison.