Synthesis of Zirconium, Hafnium, and Tantalum Complexes with Sterically Demanding Hydrazide Ligands

Abstract

The bulky hydrazine t-BuN(H)NMe2 was synthesized via hydrazone and t-BuN(H)N(H)Me intermediates as the major component in a 90:5:5 mixture consisting of t-BuN(H)NMe2, t-BuN(Me)N(H)Me, and t-BuN(Me)NMe2. Reacting the mixture with n-BuLi followed by distillation and fractional crystallization led to the isolation of the ligand precursor LiN(t-Bu)NMe2. Lithium hydrazides, LiN(R)NMe2, were reacted with metal chlorides to afford the hydrazide complexes M(N(Et)NMe2)4 (M = Zr or Hf), MCl(N(R)NMe2)3 (M = Zr, R = i-Pr or t-Bu; M = Hf, R = t-Bu), and TaCl3(N(i-Pr)NMe2)2. The X-ray crystal structures of [LiN(i-Pr)NMe2]4, [LiN(t-Bu)NMe2.THF]2, ZrCl(N(R)NMe2)3 (R = i-Pr or t-Bu), and TaCl3(N(i-Pr)NMe2)2 were determined. The structural analyses revealed that the hydrazide ligands in ZrCl(N(R)NMe2)3 (R = i-Pr or t-Bu) and TaCl3(N(i-Pr)NMe2)2 are eta2 coordinated.

Preparation of chitosan-supported urea materials and their application in some organocatalytic procedures

“…Formaldehyde tert-butyl hydrazone (FTBH) was prepared according to literature procedure (Lehn, Javed, & Hoffman, 2007). The physical and spectral properties of the synthesized compounds (R)-5,6b, (R)-5,6c, (R)-5,6d (Li, He, Qin, Feng, & Zhang, 2004), (R)-7 (Crespo-Peña et al, 2012) and 9 (Herrera, Sgarzani, Bernardi, & Ricci, 2005) are in accord with those reported.…”

N–H activation of hydrazines by a heterobimetallic Zr–Co complex: promotion of one-electron chemistry at Zr

“…The hydrazide ligands in 2 and 4 exhibit N-N distances of 1.412(2) and 1.4335(3) Å, respectively, indicating N-N single bond character, consistent with typical Zr side-on hydrazide complexes. [21][22][23][24][25][26][27] The bond lengths between Zr and the anionic hydrazido nitrogen of 2 and 4 (2.040(1) and 2.137(2) Å) are shorter than the bonds between Zr and the datively bound hydrazido nitrogen atoms (2.332(1) and 2.265(2) Å), and all distances are in the range of previously reported zirconium Z 2hydrazido complexes (2.04-2.12 Å and 2.30-2.47 Å, respectively). [21][22][23][24][25][26][27] The geometry about the anionic nitrogen atom in both compounds 2 and 4 is planar which suggests p donation of the lone pair to the zirconium atom (vide infra).…”

“…[21][22][23][24][25][26][27] The bond lengths between Zr and the anionic hydrazido nitrogen of 2 and 4 (2.040(1) and 2.137(2) Å) are shorter than the bonds between Zr and the datively bound hydrazido nitrogen atoms (2.332(1) and 2.265(2) Å), and all distances are in the range of previously reported zirconium Z 2hydrazido complexes (2.04-2.12 Å and 2.30-2.47 Å, respectively). [21][22][23][24][25][26][27] The geometry about the anionic nitrogen atom in both compounds 2 and 4 is planar which suggests p donation of the lone pair to the zirconium atom (vide infra). Notably, there are few structurally characterized examples of transition metal complexes of unsubstituted terminal Z 2 -hydrazido(1À) N 2 H 3 À ligands, [28][29][30][31] and complex 2 represents the first example with Zr.…”

Lipase Catalysed Kinetic Resolution of Racemic 1,2-Diols Containing a Chiral Quaternary Center

“…Unless otherwise noted, analytical grade solvents and commercially available reagents were used without further purification. Formaldehyde tert -butyl hydrazone [ 27 ] and organocatalyst I [ 28 ] were synthesized according to the literature. Racemic azocompounds (±)- 1 – 6b [ 24 , 26 ] and 1,2-diols (±)- 1d and (±)- 4,5d [ 29 ] exhibited the same physical and spectral properties as described in the bibliography and the nuclear magnetic resonance (NMR) data of the 1,2-diols are shown in the Supplementary Information .…”