Reactions of Tetrakis(dimethylamide)−Titanium, −Zirconium and −Hafnium with Silanes:  Synthesis of Unusual Amide Hydride Complexes and Mechanistic Studies of Titanium−Silicon−Nitride (Ti−Si−N) Formation

Abstract

M(NMe(2))(4) (M = Ti, Zr, Hf) were found to react with H(2)SiR'Ph (R' = H, Me, Ph) to yield H(2), aminosilanes, and black solids. Unusual amide hydride complexes [(Me(2)N)(3)M(mu-H)(mu-NMe(2))(2)](2)M (M = Zr, 1; Hf, 2) were observed to be intermediates and characterized by single-crystal X-ray diffraction. [(Me(2)N)(3)M(mu-D)(mu-NMe(2))(2)](2)M (1-d(2), 2-d(2)) were prepared through reactions of M(NMe(2))(4) with D(2)SiPh(2). Reactions of (Me(2)N)(3)ZrSi(SiMe(3))(3) (5) with H(2)SiR'Ph were found to give aminosilanes and (Me(2)N)(2)Zr(H)Si(SiMe(3))(3) (6). These reactions are reversible through unusual equilibria such as (Me(2)N)(3)ZrSi(SiMe(3))(3) (5) + H(2)SiPh(2) right arrow over left arrow (Me(2)N)(2)Zr(H)Si(SiMe(3))(3) (6) + HSi(NMe(2))Ph(2). The deuteride ligand in (Me(2)N)(2)Zr(D)Si(SiMe(3))(3) (6-d(1)) undergoes H-D exchange with H(2)SiR'Ph (R' = Me, H) to give 6 and HDSiR'Ph. The reaction of Ti(NMe(2))(4) with SiH(4) in chemical vapor deposition at 450 degrees C yielded thin Ti-Si-N ternary films containing TiN and Si(3)N(4). Ti(NMe(2))(4) reacts with SiH(4) at 23 degrees C to give H(2), HSi(NMe(2))(3), and a black solid. HNMe(2) was not detected in this reaction. The reaction mixture, upon heating, gave TiN and Si(3)N(4) powders. Analyses and reactivities of the black solid revealed that it contained -H and unreacted -NMe(2) ligands but no silicon-containing ligand. Ab initio quantum chemical calculations of the reactions of Ti(NR(2))(4) (R = Me, H) with SiH(4) indicated that the formation of aminosilanes and HTi(NR(2))(3) was favored. These calculations also showed that HTi(NH(2))(3) (3b) reacted with SiH(4) or H(3)Si-NH(2) in the following step to give H(2)Ti(NH(2))(2) (4b) and aminosilanes. The results in the current studies indicated that the role of SiH(4) in its reaction with Ti(NMe(2))(4) was mainly to remove amide ligands as HSi(NMe(2))(3). The removal of amide ligands is incomplete, and the reaction thus yielded "=Ti(H)(NMe(2))" as the black solid. Subsequent heating of the black solid and HSi(NMe(2))(3) may then yield TiN and Si(3)N(4), respectively, as the Ti-Si-N materials.

Synthesis, structural characterization and thermal properties of copper and silver silyl complexes

“…For each metal, both the M-C and M-Si bonds are shorter in the IMe complexes (1 and 2) than they are in the ItBu complexes (3 and 4) (Table 1). However, 1 and 2 also deviate more from linearity with C-M-Si bond angles of 171.91 (11)°and 171.6(2)°, for 1 (M = Cu) and 2 (M = Ag) respectively, than do 3 (178.60(5)°) and 4 (178.77(5)°). These differences may be due, in part, to the larger size of the ItBu ligand which leads to increased crowding around the metal center increasing the bond distances and pushing the ligands as far apart as possible in 3 and 4.…”

“…Based on the similar solid state structures obtained, all of the N-donor complexes (11)(12)(13)(14)(15) may be viewed as a cationanion pair of the form [L n M] + [M(Si(SiMe 3 ) 3 ) 2 ] − (M = Cu, Ag, n = 1, 2), where the anionic metal center interacts with the cationic center via the M-M contact. This view is supported by the observation that in complexes such as [K][Cu(Si(SiMe 3 ) 3 ) 2 ], an interaction between the Cu and K centers is observed.…”

“…1 H NMR (C 6 D 6 , δ ppm) 6.38 (s, 2H, CH), 1.58 (t, 3H, 3 J HH 7.9 Hz, SiCH 2 CH 3 ), 1.44 (s, 18H, C(CH 3 ) 3 ), 1.31 (quart of d, 2H, 3 J HH 7.9 Hz, 3 J HAg 1.6 Hz, SiCH 2 CH 3 ), 0.57 (s, 18H, SiEt(CH 3 ) 2 ). 13 (11). Neat N-methylimidazole (80 μl, 1.000 mmol) was added to a stirring off-white suspension of CuCl in THF (99 mg, 1.000 mmol; 4 mL) giving a cloudy white mixture.…”

“…9,10 Perhaps more interesting, complexes containing metal-silicon bonds have also been examined for the development of new materials. 11 Group 11 metal-silyls, specifically those of copper and silver, are a particularly interesting class of reagents. Early work on these complexes focused on the synthesis of metalsilyl species supported by phosphine ligands, but little reactivity was explored.…”

CH Bond Activation during and after the Reactions of a Metallacyclic Amide with Silanes: Formation of a μ‐Alkylidene Hydride Complex, Its H–D Exchange, and β‐H Abstraction by a Hydride Ligand

“…In our previous work, M(NMe 2 ) 4 (M=Zr, Hf) were found to react with silanes to give aminosilanes and unusual amide–hydride complexes [{(Me 2 N) 3 M(μ‐H)(μ‐NMe 2 ) 2 } 2 M], shown in Equation (2). 3b The role of silanes in these reactions is to remove amide ligands as aminosilanes and form MH bonds. We also found that the reactions of Ta(NMe 2 ) 5 with silanes afford the dinuclear Ta–hydride–imine complex [(Me 2 N) 3 Ta(μ‐H) 2 (μ‐ N ‐η 2 ‐ N , C ‐CH 2 NMe)Ta(NMe 2 ) 3 ] ( 1 ) through β‐H elimination [Eq.…”