New titanatranes and an unexpected reactivity trend in (dialkylamido)titanatranes

Abstract

The relative rates of displacement of the NR2 group in (dialkylamido)titanatranes R2NTi(OCH2CH2)3N by -OH and -SH compounds is in the order NEt2 » NMe2 > N(/-Pr)2. This unanticipated order is rationalized on the i i postulated prior formation of HR2N+Ti(OCH2CH2)3N (A), which facilitates departure of R2NH upon subsequent nucleophilic attack. For R = Et and /-Pr, the concentration of A is higher than for R = Me, owing to the basicity order Et2N s (i-Pr)2N > Me2N. The greater reactivity of A where R = Me relative to R = /-Pr is attributed to the greater steric protection from nucleophilic attack on the metal afforded by the H(/-Pr)2N+ group. The faster reactions of CF3CH2OH and PhOH compared with their sterically similar but more weakly acidic analogues CH3CH2OH and /-PrOH, respectively, support this hypothesis as do the comparable displacement rates of Et2N and Me2N in the presence of the strong nonnucleophilic base P(MeNCH2CH2)3N and the reactions of 4 and 14 with HBF4 and NH4C1 but not with NaBF4 or Me4NCl. New titanatranyl derivatives reported include five arylates, i-1 two thioarylates, and four diolates. The X-ray parameters for [/-PrSTi(OCH2CH2)3N]2 are as follows: triclinic, space group Pi (No. 2), a = 7.434(5) A, b = 12.540

Synthesis, X-ray structures, and syndiospecific polymerization behavior of styrene of new (pentamethylcyclopentadientyl) titanatranes containing modified tetradentate triethanolamine ligands

“…In contrast to the often observed oxygen-bridged dimeric structural feature for titanatranes [6,9,10,15], the crystal structures of 1e3 show monomeric character, which is consistent with their NMR spectra, presumably because of the bulky nature of the Cp* ancillary ligand. The Ti atom adopts essentially an h 5 bonding posture with Cp* ring and a tetradentate bonding mode with fully deprotonated ligands L1eL3 via a transannular interaction from the bridgehead N atom to Ti, giving a slightly distorted trigonalebipyramidal local geometry around the metal.…”

Chiral, Enantiopure Aluminum(III) and Titanium(IV) Azatranes

“…Similar results were obtained in the attempted exchange of the apical diethylamido ligand for N‐based nucleophiles. Addition of up to 10 equivalents of pyrrolidine to 5a in CDCl 3 only returned the unreacted starting materials, and additional heating resulted in partial decomposition of the complex (Scheme , path c) 51…”

Isospecific polymerization of vinyl ethers with titanium catalysts containing modified tridentate anionic donor ligands

“…Earlier work from our laboratory has already established the ability of aminodiolate‐based titanium dichlorides in C 2 and meso symmetry, aminotriolate‐based titanium chlorides in C 3 and C s symmetry, modified aminodiolate titanium dichlorides in C 2 and C s symmetry and amino‐ol‐based titanium dichloride in C 1 symmetry as effective pre‐catalysts for α‐olefin and ethylene polymerization 15–20. The literature precedence for the use of atranes as olefin polymerization catalysts is very limited and we feel that this class of atranes certainly adds interest to the non‐metallocene type of catalysts which can polymerize a variety of olefins at varying temperatures 21–27. For the polymerization of linear α‐olefins, rac ‐{N[CH 2 CH(Ph)O] 2 [NCH 2 Ph]TiCl 2 } ( 1 ‐TiCl 2 ) and meso ‐{N[CH 2 CH(Ph)O] 2 [NCH 2 Ph]TiCl 2 } ( 2 ‐TiCl 2 ) show less activity.…”