Synthesis and Characterization of Three Homoleptic Bismuth Silanolates: [Bi(OSiR3)3] (R = Me, Et,iPr)

Abstract

The bismuth tris(triorganosilanolates) [Bi(OSiR3)3] (1, R = Me; 2, R = Et; 3, R = iPr) were prepared by reaction of R3SiOH with [Bi(OtBu)3]. Compound 1 crystallizes in the triclinic space group with Z = 2 and the lattice constants a = 10.323(1) A, b = 13.805(1) A, c = 21.096(1) A and α = 91.871(4)°, β = 94.639(3)°, γ = 110.802(3)°. In the solid state compound 1 is a trimer as result of weak intermolecular bismuth-oxygen interactions with Bi–O distances in the range 2.686(6)–3.227(3) A. The coordination at the bismuth atoms Bi(1) and Bi(3) is best described as 3 + 2 coordination whereas Bi(2) shows a 3 + 3 coordination. The intramolecular Bi–O distances fall in the range 2.041(3)–2.119(3) A. Compound 3 crystallizes in the orthorhombic space group Pbcm with Z = 4 and the lattice constants a = 7.201(1) A, b = 23.367(5) A and c = 20.893(1) A, whereas the triethylsilyl-derivative 2 is liquid. In contrast to [Bi(OSiMe3)3] (1) compound 3 is monomeric in the solid state, but shows similar intramolecular Bi–O distances in the range 1.998(2)–2.065(5) A. The bismuth silanolates are highly soluble in common organic solvents and strongly moisture sensitive. Compound 1 shows the lowest thermal stability.