Synthesis and X-ray structures of amidinate, oxoamidate, and thioamidate complexes of boron

Abstract

The reactions of PhBCl2 with Li[CE(NtBu)(nBu)] or Li[CS(NtBu)(NHtBu)] (1:1 molar ratio) in toluene at 23°C produced the heterocycles Ph(Cl)B(μ-NtBu)(μ-E)C(nBu) (1a, E = NtBu; 1b, E = O; 1c, E = S) or Ph(Cl)B(μ-NtBu)(μ-S)C(NHtBu) (2), which were characterized by 1H, 11B and 13C NMR and by mass spectra. X-ray structural determinations revealed that 1a, 1c and 2 contain four-membered rings. In 2 the thioamidate ligand adopts an N,S bonding mode. Crystal data: 1a, monoclinic, space group P21, a = 8.816(3), b = 11.311(2), c = 10.168(3) Å, β = 98.86(3)°, V = 1001.7(5) Å3, Z = 2, R = 0.042, and Rw = 0.020; 1c, monoclinic, space group P21/n, a = 7.617(2), b = 11.200(1), c = 19.568(2), β = 90.74(2)°, V = 1669.1(5) Å3, Z = 4, R = 0.046, and Rw = 0.059; 2, monoclinic, space group P21/a, a = 11.357(2), b = 12.289(2), c = 12.620(3) Å, β = 95.43(2)°, V = 1753.4(5) Å3, Z = 4, R = 0.043, and Rw = 0.027. Key words: boron, amidinate, oxoamidate, thioamidate, X-ray structures.