All-Nitrogen Coordinated Amidinato/Imido Complexes of Molybdenum and Tungsten: Syntheses and Characterization

Abstract

The first all-nitrogen coordinated bis(alkylamidinato)/bis(alkylimido) complexes of molybdenum and tungsten, [Mo(NtBu)(2){(iPrN)(2)CMe}(2)]and [W(NtBu)(2){(iPrN)(2)CMe}(2)], have been synthesized and fully characterized by (1)H and (13)C NMR spectroscopy, elemental analyses, high-resolution electron impact mass spectrometry, and Fourier transform infrared spectroscopy. Density functional theory calculations of the tungsten complex allow for geometry optimization and structural characterization by assignment of the NMR data, in particular a comparison of the experimental (13)C NMR signals with the calculated ones. Both compounds sublime without decomposition at 130 °C and 1 mTorr and show rapid decomposition above 250 °C, hence representing promising vapor-phase deposition routes for metal nitride based thin-film materials.

Thermal Stability and Decomposition Pathways in Volatile Molybdenum(VI) Bis-Imides

“…For example, bis(tert-butylimido)bis(dimethylamido)molybdenum(VI) (A) has been used as a precursor for the ALD of MoNx, [11,12] MoO3, [13,14] MoS2, [15][16][17] MoCxNy, [18,19] TiMoxNy, [20] and Al:MoS2. [21] N,N'-chelating ligands have also been used to prepare volatile bis(tert-butylimido)molybdenum(VI) compounds, such as amidinates (B), [22] pyrazolates (C), [10] guanidinates (D), [23] and diazabutadienyls (E). [24] However, only the amidinate B has been used for ALD to prepare MoO3 films with O3.…”

Synthesis of Mono‐Imido Tungsten Complexes Directly from WCl6

“…This requires development of new precursors of metal-organic nature and mild reaction by-products. As a result, several tungsten complexes of nitrogen-bound ligands (including amide, [17,18,33] imide, [18][19][20][21][22][23][24][25] hydrazido, [26,27] amidinate, [20] and guanidinate [28][29][30] ligands) as single-source precursors were developed. [31] These precursors afforded halogenand oxygen-free tungsten nitride or tungsten carbonitride films when used in the ALD/CVD process in the presence of appropriate reductive gases (H 2 or NH 3 ).…”

MOCVD of tungsten nitride thin films: Comparison of precursor performance and film characteristics

“…Amido–imido complexes of tungsten such as [W(N t Bu) 2 (NH t Bu) 2 ] and [Cl 4 (RCN)W(NR′)] (R = CH 3 , Ph; R′ = i Pr, C 3 H 5 , Ph) have been used as MOCVD precursors under single source precursor (SSP) conditions or in combination with NH 3 as reactive gas for the deposition of WN thin films. Earlier, we demonstrated that all nitrogen coordinated amidinato‐based tungsten complexes [W(N t Bu) 2 {( i PrN) 2 CMe} 2 ] and guanidinato‐based tungsten compounds like [W(N t Bu) 2 (NMe 2 ){( i PrN) 2 CNMe 2 }] and [W(N t Bu) 2 (H){( i PrN) 2 CNMe 2 }] can serve as potential precursor for the deposition of WN thin films in a home built CVD reactor .…”