Imido Complexes Derived from the Reactions of Niobium and Tantalum Pentachlorides with Primary Amines: Relevance to the Chemical Vapor Deposition of Metal Nitride Films

Publisher Website
Google Scholar
Abstract
Reactions of niobium and tantalum pentachlorides with tert-butylamine (≥6 equiv) in benzene afford the dimeric imido complexes [NbCl2(NtBu)(NHtBu)(NH2tBu)]2 (90%) and [TaCl2(NtBu)(NHtBu)(NH2tBu)]2 (79%). The niobium complex exists as two isomers in solution, while the tantalum complex is composed of three major isomers and at least two minor isomers. Analogous treatments with isopropylamine (≥7 equiv) give the monomeric complexes NbCl2(NiPr)(NHiPr)(NH2iPr)2 (84%) and TaCl2(NiPr)(NHiPr)(NH2iPr)2 (84%). The monomeric complexes are unaffected by treatment with excess isopropylamine, while the dimeric complexes are cleaved to the monomers MCl2(NtBu)(NHtBu)(NH2tBu)2 upon addition of excess tert-butylamine in chloroform solution. Treatment of niobium and tantalum pentachlorides with 2,6-diisopropylaniline affords insoluble precipitates of [NH3(2,6-(CH(CH3)2)2C6H3)]2[NbCl5(N(2,6-(CH(CH3)2)2C6H3))] (100%) and [NH3(2,6-(CH(CH3)2)2C6H3)]2[TaCl5(N(2,6-(CH(CH3)2)2C6H3))] (100%), which react with 4-tert-butylpyridine to afford the soluble complexes [4-t-C4H9C5H4NH]2[NbCl5(N(2,6-(CH(CH3)2)2C6H3))] (45%) and [4-t-C4H9C5H4NH]2[TaCl5(N(2,6-(CH(CH3)2)2C6H3))] (44%). Sublimation of [NbCl2(NtBu)(NHtBu)(NH2tBu)]2, MCl2(NiPr)(NHiPr)(NH2iPr)2, and [NH3(2,6-(CH(CH3)2)2C6H3)]2[MCl5(N(2,6-(CH(CH3)2)2C6H3))] leads to decomposition to give [MCl3(NR)(NH2R)]2 as sublimates (32−49%), leaving complexes of the proposed formulation MCl(NR)2 as nonvolatile residues. By contrast, [TaCl2(NtBu)(NHtBu)(NH2tBu)]2 sublimes without chemical reaction. Analysis of the organic products obtained from thermal decomposition of [NbCl2(NtBu)(NHtBu)(NH2tBu)]2 showed isobutylene and tert-butylamine in a 2.2:1 ratio. Mass spectra of [NbCl2(NtBu)(NHtBu)(NH2tBu)]2, [TaCl2(NtBu)(NHtBu)(NH2tBu)]2, and [NbCl3(NiPr)(NH2iPr)]2 showed the presence of dimeric imido complexes, monomeric imido complexes, and nitrido complexes, implying that such species are important gas phase species in CVD processes utilizing these molecular precursors. The crystal structures of [4-t-C4H9C5H4NH]2[NbCl5(N(2,6-(CH(CH3)2)2C6H3))], [NbCl3(NiPr)(NH2iPr)]2, [NbCl3(N(2,6-(CH(CH3)2)2C6H3))(NH2(2,6-(CH(CH3)2)2C6H3))]2, and [TaCl3(N(2,6-(CH(CH3)2)2C6H3))(NH2(2,6-(CH(CH3)2)2C6H3))]2 were determined. [4-t-C4H9C5H4NH]2[NbCl5(N(2,6-(CH(CH3)2)2C6H3))] crystallizes in the space group P21/c with a = 12.448(3) Å, b = 10.363(3) Å, c = 28.228(3) Å, β = 94.92(1)°, V = 3628(5) Å3, and Z = 4. [NbCl3(NiPr)(NH2iPr)]2 crystallizes in the space group P21/c with a = 9.586(4) Å, b = 12.385(4) Å, c = 11.695(4) Å, β = 112.89(2)°, V = 1279.0(6) Å3, and Z = 2. [NbCl3(N(2,6-(CH(CH3)2)2C6H3))(NH2(2,6-(CH(CH3)2)2C6H3))]2 crystallizes in the space group P21/n with a = 10.285(3) Å, b = 11.208(3) Å, c = 23.867(6) Å, β = 97.53°, V = 2727(1) Å3, and Z = 2. [TaCl3(N(2,6-(CH(CH3)2)2C6H3))(NH2(2,6-(CH(CH3)2)2C6H3))]2 crystallizes in the space group P21/n with a = 10.273(1) Å, b = 11.241(2) Å, c = 23.929(7) Å, β = 97.69(2)°, V = 2695(2) Å3, and Z = 2. These findings are discussed in the context of niobium and tantalum nitride film depositions from molecular...

This publication has 28 references indexed in Scilit: