Synthesis and characterization of three homoleptic bismuth silanolates: [Bi(OSiR3)(3)] (R = Me, Et, iPr)

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 P (1) over bar with Z = 2 and the lattice constants a = 10.323(1) angstrom, b = 13.805(1)angstrom, c = 21.096(1) angstrom and alpha = 91.871(4)degrees, beta = 94.639(3)degrees, gamma = 110.802(3)degrees. In the solid state compound I is a trimer as result of weak intermolecular bismuth-oxygen interactions with Bi-O distances in the range 2.686(6)-3.227(3) angstrom. 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) angstrom. Compound 3 crystallizes in the orthorhombic space group Pbcm with Z = 4 and the lattice constants a = 7.201(1) angstrom, b = 23.367(5) angstrom and c = 20.893(1) angstrom, 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) angstrom. The bismuth silanolates are highly soluble in common organic solvents and strongly moisture sensitive. Compound 1 shows the lowest thermal stability.