Synthesis, Characterization, and Materials Chemistry of Group 4 Silylimides

This paper focuses on the development of potential single source precursors for M–N–Si (M = Ti, Zr or Hf) thin films. The titanium, zirconium, and hafnium silylimides (Me2N)2MNSiR1R2R3 [R1 = R2 = R3 = Ph, M = Ti­(1), Zr (2), Hf (3); R1 = R2 = R3 = Et, M = Ti (4), Zr (5), Hf (6); R1 = R2 = Me, R3 = tBu, M = Ti (7), Zr (8), Hf (9); R1 = R2 = R3 = NMe2, M = Ti (10), Zr (11), Hf (12)] have been synthesized by the reaction of M­(NMe2)4 and R3R2R1SiNH2. All compounds are notably sensitive to air and moisture. Compounds 1, 2, 4, and 7–10 have been structurally characterized, and all are dimeric, with the general formula [M­(NMe2)2(μ-NSiR3)]2, in which the μ2-NSiR3 groups bridges two four-coordinate metal centers. The hafnium compound 3 possesses the same basic dimeric structure but shows additional incorporation of liberated HNMe2 bonded to one metal. Compounds 11 and 12 are also both dimeric but also incorporate additional μ2-NMe2 groups, which bridge Si and either Zr or Hf metal centers in the solid state. The Zr and Hf metal centers are both five-coordinated in these species. Aerosol-assisted CVD (AA-CVD) using 4–7 and 9–12 as precursors generates amorphous films containing M, N, Si, C, and O; the films are dominated by MO2 with smaller contributions from MN, MC and MSiON based on XPS binding energies.本研究聚焦于M-N-Si（M=钛(Ti)、锆(Zr)或铪(Hf)）系薄膜的潜在单源前驱体开发。通过M(NMe₂)₄与R³R²R¹SiNH₂的反应，合成了钛、锆、铪的硅酰亚胺类化合物(Me₂N)₂MNSiR¹R²R³，各取代基与金属的组合如下：[R¹=R²=R³=苯基(Ph)时，M=钛为化合物1、锆为化合物2、铪为化合物3；R¹=R²=R³=乙基(Et)时，M=钛为化合物4、锆为化合物5、铪为化合物6；R¹=R²=甲基(Me)、R³=叔丁基(tBu)时，M=钛为化合物7、锆为化合物8、铪为化合物9；R¹=R²=R³=二甲氨基(NMe₂)时，M=钛为化合物10、锆为化合物11、铪为化合物12]。所有目标化合物对空气与湿气均具有显著敏感性。已对化合物1、2、4及7至10进行结构表征，结果显示所有化合物均为二聚体，通式为[M(NMe₂)₂(μ-NSiR³)]₂，其中μ₂-NSiR³桥联两个四配位金属中心。铪基化合物3具有相同的基础二聚体结构，但额外结合了游离生成的HNMe₂分子并配位至其中一个金属中心。化合物11与12同样为二聚体结构，且引入了额外的μ₂-NMe₂桥联基团，在固态下该基团同时桥连硅原子与锆或铪金属中心。此类物种中的锆与铪金属中心均为五配位结构。以化合物4至7及9至12作为前驱体，通过气溶胶辅助化学气相沉积(Aerosol-assisted CVD, AA-CVD)可制备出含M、N、Si、C及O的无定形薄膜；基于X射线光电子能谱(X-ray Photoelectron Spectroscopy, XPS)的结合能分析结果，该类薄膜主要成分为MO₂，另有少量MN、MC及MSiON组分。