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Addition of 2.0 equiv of Na(silox) to TiCl4(THF)2 afforded (silox)2TiCl2 (1), which yielded (silox)2(tBu3SiNH)TiCl (2-Cl) upon treatment with tBu3SiNLi. Grignard or alkyllithium additions to 2-Cl or 1,2-RH-addition to transient (silox)2TiNSitBu3 (3) produced (silox)2(tBu3SiNH)TiR (2-R; R = Me, Et, CH2Ph = Bz, CHCH2 = Vy, cBu, nBu, Ph, H, cPr, cPe, CH2-3,5-Me2C6H3 = Mes, neoHex, cHex, η3-H2CHCH2, η3-H2CCHCHMe). Insertions of C2H4, butadiene, HC2H, and HC2 tBu into the titanium−hydride bond of 2-H generated (silox)2(tBu3SiNH)TiR (2-R; R = Et, η3-H2CCHCHMe, Vy, E-CHCHtBu). Trapping of 3 by donors L afforded (silox)2LTiNSitBu3 (3-L; L = OEt2, THF (X-ray, two independent molecules:  d(TiN) = 1.772(3), 1.783(3) Å), py, PMe3, NMe3, NEt3) and RC2R‘ = HC2H, MeC2Me, EtC2Et, HC2 tBu) and Kinetics of 1,2-RH-elimination from 2-R revealed a first-order process (24.8 °C):  R = Bz < Mes < H < Me (1.54(10) × 10-5 s-1) < neoHex < Et < nBu < cBu < cPe < cHex < cPr < Vy < Ph. Kinetics data, large 1,2-RH/D-elimination KIE's (e.g., MeH/D, 13.7(9), 24.8 °C), and Eyring parameters (e.g., 2-Me, ΔH ⧧ = 20.2(12) kcal/mol, ΔS ⧧ = −12(4) eu) portray a four-center, concerted transition state where the N···H···R linkage is nearly linear. Equilibrium measurements led to the following relative standard free energy scale:  2-cHex > 2-cPe > 2-nPr ∼ 2-nBu > 2-neoHex > 2-Et > 2-cBu > 2-CH2SiMe3 > 2-Ph > 2-Me > 2-Bz > 2-cPr ∼ 2-Mes > 2-Vy > 3-C2H4 > 3-NEt3 > 2-H > 3-OEt2 > 3-EtC2Et >3-MeC2Me > 3-THF > 3-NMe3 > 3-PMe3 > 3-py. A correlation of D(TiR)rel to D(RH) revealed greater differences in titanium−carbon bond energies. THF loss from 3-THF allowed a rough estimate of ΔG°(3). Using thermochemical cycles, relative activation energies for 1,2-RH-addition were assessed:  cHexH > cPeH > nBuH > neoHexH > EtH > BzH > cBuH > MesH > MeH > PhH > cPrH > VyH > 3-C2H4 formation > H2. On the basis of a parabolic model, C−H bond activation selectivities are influenced by the relative ground state energies of 2-R and a parameter representing the reaction coordinate. A more compressed reaction coordinate for sp2- vs sp3-substrates eases their activation.

ingness to disclose results prior to publication and their agreement to concurrent publication. Supplementary Material Available: Spectroscopic and analytical data for complexes la-c, 2a, 3b, 4a-c, 5bc, 6b, 8a-c, and 9b and details of the structure determination for complexes 2a and 9b, including experimental description, ortep drawings showing full atomic numbering and packing in the crystal, crystal and data collection parameters, general temperature factor expressions (fi's), positional parameters and their estimated standard deviations, and intramolecular distances and angles (35 pages); tables of observed and calculated structure factors for 2a and 9a (24 pages). Ordering information is given on any current masthead page.Methane and Benzene Activation via Transient (t-Bu3SiNH)2Zr=NSi-f-Bu3

Current interest in the reactivity of early transition metalligand multiple bonds,1 specifically those of metal-imido complexes,2 has centered around the 1,2-addition of various substrates to the M=N bond.3-13 Transient, electrophilic group 4 (e.g., Cp2Zr=NR,3-6 (tBu3SiNH)2Zr=NSitBu3,7 (tBu3SiNH)-XTi=NSi'Bu3)8 and 5 (e.g., (1Bu3SiNH)M(=NSi'Bu3)2, = Ta,9 V)10-11 complexes containing imido functionalities have exhibited intriguing alkane7•9•11 and arene activations3-11 of theoretical interest,16 2 + 2 cycloadditions,3-6•10•*3 catalytic amination of alkynes,5 and corresponding adduct chemistry.3-17 Reported herein is a chemically diverse titanium imido system, developed through inclusion of ancillary silox (lBu3SiO-) ligands.Chloride (silox)2('Bu3SiNH)TiCl (l)18 was prepared in 76% yield by sequential, stoichiometric additions of Na(silox) and 'BujSiNHLi to TiCl4(THF)2. Alkylation (i.e., RLi, RMgX) of 1 afforded colorless (silox)2('Bu3SiNH)TiR (2-R, R = Me (76%), Et (51%), CH2Ph (yellow, 58%),18 Vy = CH=CH2 (30%)).191,2-RH-Elimination from 2-R in CéD6 gave (silox)2('Bu3SiND)-TiCeDs (2-(ND)-C6D5), but with lower activation energies vis-

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