Rare Earth and Main Group Metal Poly(hydrosilyl) Compounds

The potassium poly(hydrosilyl) compound KSi(SiHMe2)(3), which contains three beta-SiH groups, is synthesized by the reaction of Si(SiHMe2)(4) and KOtBu. A single-crystal X-ray diffraction study reveals chains composed of head-to-tail KSi(SiHMe2)(3) monomers. This potassium poly(hydrosilyl) anion reacts with divalent metal halide salts in THF to form the bis(silyl) compounds Mg{Si-(SiHMe2)(3)}(2)THF2 (1 center dot THF2), Ca{Si(SiHMe2)(3)}(2)THF3 (2 center dot THF3), and Yb{Si(SiHMe2)(3)}(2)THF3 (3 center dot THF3). A trivalent yttrium bis(silyl), as part of a KCl-containing polymeric chain, is supported by K(sic)H-Si bridging interactions. The N donors pyridine (py) and dimethylaminopyridine (DMAP) readily substitute THF, giving tetrahedral magnesium and octahedral calcium silyl compounds. The one-bond silicon-hydrogen coupling constants ((1)J(SiH)), infrared stretching frequencies (nu(SiH)), and solid-state structures of 2 center dot py(4) and 3 center dot THF3 indicate classical two center-two electron bonding between the metal center and the silyl ligand, as well as terminal (nonbridging) Si-H bonds within the silyl ligands. The magnesium and calcium compounds readily react with the Lewis acids PhB(C6F5)(2) and B(C6F5)(3) to give hydridoborate salts, whereas {kappa(3)-To(M)}(2)Yb (5) (To(M) = tris(4,4-dimethyl-2-oxazolinyl)phenyl borate) is formed by reaction of TlTo(M) and 3 center dot THF3.