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-
The (13)C NMR spectra of two different iodoalkynes, 1-iodo-1-hexyne (1) and diiodoethyne (2), exhibit a strong solvent dependence. Comparisons of the data with several common empirical models, including Gutmann's Donor numbers, Reichardt's E(N)(T), and Taft and Kamlet's beta and pi, demonstrate that this solvent effect arises from a specific acid-base interaction. Solvent basicity measures such as Donor numbers and beta values correlate well with the alpha-carbon chemical shift of 1, but polarity measures such as E(N)(T) and pi do not correlate. The similarity of the solvent effect for 1 and 2 suggests that carbon-carbon bond polarization may not play a role in the change in chemical shift, as previously hypothesized.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.