Synthesis of Tantalum(V) Amido Silyl Complexes and the Unexpected Formation of (Me₂N)₃Ta(η²-ONMe₂)[OSi(SiMe₃)₃] from the Reaction of (Me₂N)₄Ta[Si(SiMe₃)₃] with O₂

Abstract

The synthesis and characterization of amido silyl complexes of tantalum(V) free of π-anionic ligands are reported. The amido silyl chloride complexes (Me 2 N) 3 Ta(SiR 3 )Cl [SiR 3 ) Si(SiMe 3 ) 3 (1a), SiPh 2 Bu t (2)] were prepared from (Me 2 N) 3 TaCl 2 and the corresponding silyllithium reagents Li(THF) 3 Si(SiMe 3 ) 3 and Li(THF) 3 SiPh 2 Bu t . The amido silyl complexes (Me 2 N) 4 Ta-(SiR 3 ) [SiR 3 ) Si(SiMe 3 ) 3 (3), SiPh 2 Bu t (4)] were synthesized by the reactions of (Me 2 N) 4 -TaCl with Li(THF) 3 SiR 3 . Complex 3 was found to react with 1 equiv of O 2 to give an oxidation product (Me 2 N) 3 Ta(η 2 -ONMe 2 )[OSi(SiMe 3 ) 3 ] (5), and the structure of 5 was confirmed by X-ray crystallography. The spectroscopic data and crystal structure determination reveal that the coordination geometry around Ta metal in 1a and 2-4 is trigonal bipyramid with silyl ligands in an equatorial position.Early-transition-metal amido complexes have attracted much attention in recent years in part because of their important applications as precursors in chemical vapor deposition of microelectronic metal nitride (MN x ) and M-Si-N ternary films as diffusion barriers in Sibased microelectronic devices. 1,2 In particular, M-Si-N ternary films, which are often amorphous, have shown better diffusion barrier properties than, e.g., TiN films that are usually polycrystalline and thus have grain boundaries for diffusion. 1c,d,2 Although numerous well-

Crystal structure of chlorido{[3-(η5-cyclopenta-dienyl)-2,2,3-trimethyl-1-phenylbutylidene] azanido-κN}[η2(N,O)-N,N-dimethylhydroxylaminato]titanium(IV), C20H27ClN2OTi

“…The η 2 -N,N-dimethylhydroxylaminato moiety (cf. the figure) formed from the original dimethylamido ligand by an unknown mechanism, however, adventitious oxidation by air might be suspected as a plausible pathway since a similar transformation of the dimethylamido ligand by dioxygen was observed for tantalum(V) amido silyl complexes [8]. Related cyclopentadienyl titanium complexes with the η 2 -hydroxylaminato moiety were previously obtained by different approaches including reactions of Me 2 NOSiMe 3 with CpTiCl 3 [9] or N,N-dialkylhydroxylamines or nitroso compounds with methyl titanium precursors [10,11].…”

Reactivities of d0 transition metal complexes toward oxygen: Synthetic and mechanistic studies

“…Calculated energies of the intermediates are given in ref. 12. [13,14] The amide silyl complexes are of interest to further our understanding of the reactions between O 2 and d 0 complexes. In addition, such reactions may lead to mixed metal oxides-SiO 2 which have been studied as insulating gate materials [24] .…”

“…(Me 2 N) 4 TaSi(SiMe 3 ) 3 (11) [14] readily reacts with O 2 at room temperature, yielding bright-yellow oxidation product (Me 2 N) 3 Ta(η 2 -ONMe 2 )[OSi(SiMe 3 ) 3 ] (13) (eq. (2)).…”

“…In comparison, W(NMe 2 ) 6 is inert to oxygen. We have also investigated the reactions of O 2 with tantalum silyl amide complexes (Me 2 N) 4 TaSiR 3 [R 3 = (SiMe 3 ) 3 , 11; Bu t Ph 2 , 12] that give (Me 2 N) 3 Ta(η 2 -ONMe 2 ) [OSi(SiMe 3 ) 3 ] (13) [13] and (Me 2 N) 4 Ta(OSiBu t Ph 2 ) (15), (Me 2 N) 3 Ta(ONMe 2 )(OSiBu t Ph 2 ) (16), and the unusual μ-oxo amino (Me 2 N) 2 (Ph 2 Bu t SiO) 2 (μ,η 2 -Me 2 NCH 2 NMe) 2 Ta 2 (μ-O) 2 (14) [14] . However, when an equilibrium mixture of silyl alkylidyne (Bu t CH 2 ) 2 W(≡CBu t )(SiBu t Ph 2 ) (17a) and its bis(alkylidene) tautomer (Bu t CH 2 )W (=CHBu t ) 2 (SiBu t Ph 2 ) (17b) is exposed to O 2 , migration of the silyl ligand to the alkylidyne ligand occurs yielding silyl-substituted alkylidene oxo complex (Bu t CH 2 ) 2 W(=O)[=CBu t (SiBu t Ph 2 )] (18) [15,16] .…”

Lead(II) Siloxides

“…We therefore turned our attention to the bulkiers ilanol (Me 3 Si) 3 SiOH, used previously to prepareavariety of transition metal siloxides, [3b] and, very recently,two bariumsiloxides. [10,11] The siloxide [{RO F }PbOSi(SiMe 3 ) 3 ]( 1)i sa vailable in 70-75% yields upon reaction of [{RO F }PbN(SiMe 3 ) 2 ]w ith one equivalent of (Me 3 Si) 3 SiOH in petroleum ether.T his colourless complex crystallised as al ooselya ssociated O-bridgedd imer 1 2 (vide infra), but 1 HDOSYN MR data recordedi n[ D 6 ]benzene suggest the presence of as ingle, mononuclear species in solution in this solvent. The complex is characterised by as ingle resonance at d207 Pb 2130 ppm by 207 Pb NMR spectroscopy, that is, shielded by 700 ppm compared to the boryloxide [{RO F }PbOB{CH(SiMe 3 ) 2 } 2 ].…”