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-

The reactions of tantalum alkylidene complexes (RCH 2 ) 3 Ta(L)dCHR (1) and RCH 2 Ta(L) 2 -[dCHR] 2 (3) (R ) SiMe 3 , L ) PMe 3 ) with phenylsilanes H 2 SiR′Ph (R′ ) Me, Ph) and (PhSiH 2 ) 2 -CH 2 were found to produce bis(silyl)-substituted alkylidene complexes (RCH 2 ) 3 TadCR-(SiHR′Ph) (4) and novel metallasilacyclobutadiene and metalladisilacyclohexadiene complexes. Reaction of the mixed-ligand trimethylsilylmethyl neopentylidene complex RCH 2 Ta(L) 2 [d CHBu t ] 2 ( 6) with H 2 SiMePh also yielded a metallasilacyclobutadiene complex, but reaction of the neopenyl neopentylidene complex Bu t CH 2 Ta(L) 2 [dCHBu t ] 2 (2) with H 2 SiMePh yielded unidentified products. Deuterium-labeling and kinetic studies of the conversion of 1 f 4 were found to be consistent with a dissociative mechanism. The structures of the novel metallacyclic complexes 5a, 5b, 7, and 8 were determined by X-ray crystallography.

Silyl dianions [(Me 3 Si) 2 Si(CH 2 ) n Si( SiMe 3 ) 2 ] 2-(n ) 1, 4; 2, 5; 3, 6) as [K(18-crown-6)] + salts have been prepared by reactions of (Me 3 Si) 3 Si(CH 2 ) n Si(SiMe 3 ) 3 (n ) 1, 1; 2, 2; 3, 3) with t-BuOK and 18-crown-6 in DME. Characterization of these new silyl dianions, X-ray crystal structures of 2, 3, and 5, and improved synthesis of 1-3 are reported.

No abstract

The reaction of Cu(ClO(4))(2) x 6H(2)O, NaAsF(6) and excess pyrazole yields hexakis(pyrazole-kappa N(2))copper(II) bis(hexafluoroarsenate), [Cu(C(3)H(4)N(2))(6)](AsF(6))(2) or [Cu(pzH)(6)](AsF(6))(2) (pzH is pyrazole), (I). The analogous hexakis(pyrazole-kappa N(2))copper(II) hexafluorophosphate perchlorate complex, [Cu(C(3)H(4)N(2))(6)](PF(6))(1.29)(ClO(4))(0.71) or [Cu(pzH)(6)](PF(6))(1.29)(ClO(4))(0.71), (II), is obtained in a similar fashion, using KPF(6) in place of NaAsF(6). Both compounds contain the hitherto unknown [Cu(pzH)(6)](2+) complex cation, in which the copper(II) ion lies at the center of a regular octahedron of coordinated N atoms. The cation has crystallographically imposed -3 symmetry. The X-ray data indicate that the lack of the expected distortion can be accounted for by the presence of either static Jahn-Teller disorder or dynamic Jahn-Teller distortion.