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Reaction of TaCl2(═NSiMe3)[N(SiMe3)2] (1) with alkylating reagents form the alkyl amide imide complexes TaR2(═NSiMe3)[N(SiMe3)2] (R = Me (2), CH2Ph (3)) and mixed amide imide compounds Ta(NR′2)2(═NSiMe3)[N(SiMe3)2] (R′ = Me (4), Et (5)). The reaction of 2 and 0.5 equiv of O2 leads to preferential oxygen insertion into one Ta-Me bond, yielding the alkoxy-bridged alkyl dimer Ta2(μ-OMe)2Me2(═NSiMe3)2[N(SiMe3)2]2 (6) as cis and trans isomers. Crystallization of the cis-6 and trans-6 mixture gave only crystals of trans-6. When the crystals of trans-6 were dissolved in benzene-d6, conversion of trans-6 to cis-6 occurred until the trans-6 ⇌ cis-6 equilibrium was reached with Keq = 0.79(0.02) at 25.0(0.1) °C. Kinetic studies of the exchange gave the rate constants k = 0.018(0.002) min-1 for the trans-6 → cis-6 conversion and k′ = 0.022(0.002) min-1 for the reverse cis-6 → trans-6 conversion at 25.0(0.1) °C. Complex 6 reacts with additional O2, forming the dialkoxy dimer Ta2(μ-OMe)2(OMe)2(═NSiMe3)2[N(SiMe3)2]2 (7) as cis and trans isomers. Solid-state structures of 3 and trans-6 have been determined by X-ray diffraction analyses. The mixed amide imide compounds Ta(NR′2)2(═NSiMe3)[N(SiMe3)2] (R′ = Me (4), Et (5)) have also been prepared by salt metathesis reactions employing TaCl3[N(SiMe3)2]2 (8). The pathway from 8 to 4 and 5 eliminates Me3Si-NR′2 (R′ = Me, Et), converting the amide N(SiMe3)2 ligand to the imide ═NSiMe3 ligand. Such intramolecular imidation is rare. The mechanism of this process has been computationally probed, and α-elimination involving the mixed amide species TaCl2(NMe2)[N(SiMe3)2]2 (9) is discussed. Diffusion-ordered spectroscopy (DOSY) studies of 1-6 and 8 show that only the alkoxy-bridged cis-6 and trans-6 are dimers in benzene-d6 solution at 25 °C. [ABSTRACT FROM AUTHOR]

Direct insertion of 1 equiv of CyNCNCy(1; Cy = cyclohexyl) into the Zr–NMe2bonds in (Me2N)3Zr[N(SiMe3)2] (2) and (Me2N)3Zr[Si(SiMe3)3] (3) gave exclusively [CyNC(NMe2)NCy]Zr(NMe2)2[N(SiMe3)2] (5) and [CyNC(NMe2)NCy]Zr(NMe2)2[Si(SiMe3)3] (6), respectively. The reactionbetween 2and guanidine CyNHC(NMe2)NCy(9) gave 5and HNMe2throughthe preferred cleavage of a Zr–NMe2bond in 2. The reaction between 3and 9ledto the preferred cleavage of the Zr–Si(SiMe3)3bond in 3, yielding [CyNC(NMe2)NCy]Zr(NMe2)3(7) and HSi(SiMe3)3and, upon cleavage of another Zr–NMe2bond,forming [CyNC(NMe2)NCy]2Zr(NMe2)2(8). The aminolysis of Zr(NMe2)4(4) by 9first afforded 7and then 8. The structures of 5, 6, and 9have been determined by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Group 4 amide chloride complexes (Me2N)2Hf[N(SiMe3)2]Cl (1b), [(Me3Si)2N]2MCl2Li(THF)3Cl (M = Zr, 2a; Hf, 2b), and [(Me3Si)2N]2MCl2(THF) (M = Zr, 3a; Hf, 3b) and their X-ray crystal structures are reported. An improved synthesis of {[(Me3Si)2N]Ti(μ-NSiMe3)Cl}2(4) and its use to prepare amide imide {[(Me3Si)2N]Ti(μ-NSiMe3)(NMe2)}2(5) are also presented. X-ray crystal structures of 5and previously reported complexes (Me2N)2Zr[N(SiMe3)2]Cl (1a), [(Me3Si)2N]2TiCl2(6), and [(Me3Si)2N]ZrCl3(THF)2(7) have been determined. Both 1aand 1bare dimers {[(Me3Si)2N]-(Me2N)2M(μ-Cl)}2(M = Zr, Hf) in the solid state. [ABSTRACT FROM AUTHOR]

Amidinate amide complexes M[CyNC(Me)NCy]2(NR2)2(M = Ti, R = Me (1); M = Zr, R = Me (2), R = Et, (3); M = Hf, R = Me (4); Cy = cyclohexyl) have been prepared, and their crystal structures show distorted-octahedral coordination spheres. Variable-temperature NMR studies give ΔH⧧= 2.8(0.2) kcal mol−1, ΔS⧧= −36(1) eu and ΔH⧧= 0.5(0.3) kcal mol−1, ΔS⧧= −44(1) eu for interconversions in 2and 3, respectively. [ABSTRACT FROM AUTHOR]

Reactions of TaCl(NMe2)4(2) with LiNR2(R = SiMe3, Et), yielding Ta(NMe2)4(NR2) (R = SiMe3, 4; Et, 7), Ta(NMe2)5(1), (Me2N)3TaN(SiMe3)SiMe2CH2(5), and Ta(NMe2)3(NEt2)2(8), respectively, suggest the presence of an equilibrium among TaCl(NMe2)4(2), Ta(NMe2)5(1), and Ta2(μ-Cl)2(NMe2)6Cl2(3): 2 2 ⇌ 1+ 0.5 3. New products Ta(NMe2)4(NR2) have been characterized. Ta(NMe2)4(NEt2) (7), Ta(NMe2)5(1), and Ta(NMe2)3(NEt2)2(8) are in a slow exchange: 2 7 ⇌ 1+ 8with an equilibrium constant of Keq= 0.25(0.01) at 90 °C. The following are also reported: X-ray crystal structure and a one-step synthesis of TaCl(NMe2)4(2), reaction of 2with H2O giving Ta2(μ-Cl)2(μ-O)(NMe2)6(9), X-ray structure of 9, and preparation of LiNEt2solid. [ABSTRACT FROM AUTHOR]

Reactions of MCl 5(M = Nb, Ta) with LiNMe 2have been found to yield M(NMe 2) 4(η 2-MeNCH 2NMe 2) (M = Nb, 2a; Ta, 2b) containing a chelating ligand (dimethylaminomethylene)methylamide, as confirmed by NMR spectroscopy, DFT calculations, and their reactivity studies. [ABSTRACT FROM AUTHOR]