Synthesis and Characterization of Group 4 Amido Silyl Complexes Free of Anionic π-Ligands

Abstract

A series of early-transition-metal silyl complexes free of anionic π-ligands such as cyclopentadienyl (Cp = η5-C5H5) have been synthesized. These Cp-free complexes (Me2N)3MSi(SiMe3)3 [M = Zr (1), Hf (2)], (Me2N)3TiSiPh2But (3), (Me2N)3ZrSiPh2But·0.5THF (4), (Me2N)3HfSiPh2But·nTHF [n = 0.5 (5a), 1 (5b)], and (Me2N)2[(Me3Si)2N]ZrSiR3 [SiR3 = Si(SiMe3)3 (7), SiPh2But (8)] were prepared by metathetic reactions of chloro triamido complexes (Me2N)3MCl (M = Ti, Zr, Hf) or (Me2N)2[(Me3Si)2N]ZrCl (6) with silyllithium reagents Li(THF)3Si(SiMe3)3 or Li(THF)3SiPh2But. The structures of 1, 3, 4, 5b, and 8 have been determined by X-ray crystallography and show that 1, 3, and 8 adopt a distorted tetrahedral coordination geometry while 4 and 5b have a distorted trigonal bipyramidal geometry around the metal. The unit cell parameters are as follows. 1: space group R3c, a = 15.505(2) Å, c = 19.308(4) Å, V = 4019.9(13) Å3, Z = 6. 3: space group P21, a = 8.633(5) Å, b = 14.790(7) Å, c = 9.388(4) Å, β = 92.44(4)°, V = 1197.6(10) Å3, Z = 2. 4: space group Pbca, a = 16.538(9) Å, b = 17.282(7) Å, c = 18.566(8) Å, V = 5306(4) Å3, Z = 8. 5b: space group Pna21, a = 17.463(6) Å, b = 9.453(3) Å, c = 17.800(6) Å, V = 2938(2) Å3, Z = 4. 8: space group Pca21, a = 19.775(5) Å, b = 10.182(2) Å, c = 15.752(5) Å, V = 3172(2) Å3, Z = 4. The M−Si bond distances for 1, 3, 4, 5b, and 8 are 2.781(2), 2.635(2), 2.803(2), 2.807(4), and 2.860(2) Å, respectively. The Zr−Si bond in 8, to our knowledge, is the longest reported Zr−Si bond.