Ligand Bridged and Bis‐ligand Coordinated Titanium Complexes: Synthesis, Structure and Relevance to Phenylacetylene Hydroanilination Catalysis

Abstract

Two ligand bridged binuclear titanium complexes Ti 2 (bppda) 3 (NMe 2 ) 2 •3THF (1) and Ti 2 (bppda) 3 (NEt 2 ) 2 •3THF (2) and one bis-ligand coordinated mononuclear complex Ti(bppda) 2 (3) (ligand: H 2 bppda＝N,N'-Bis(2-pyrrylmethylidene)-1,2-phenylenediamine) were synthesized by adjusting the ratio of the starting materials and the reaction speed. The complexes were fully characterized with NMR, elemental analysis and X-ray crystal diffraction. The catalytic activity of the complex 1 to phenylacetylene hydroanilination reaction was also investigated.

Ligands with Two Monoanionic N,N‐Binding Sites: Synthesis and Coordination Chemistry

“…Amongt hem, the dinuclear titanium complex XX (Figure 24) did show catalytic activity for the polymerization of rac-lactide [120] and the cobalt and manganese complexes weref ound to readily activate O 2 . [114,118] When three ligand molecules frame two metals,d inuclear complexes of type D are obtained.E xamples of titanium [117] and yttrium [115] speciesh ave been reported and the titaniumc omplex catalyzes the hydroamination reactionofp henylacetylene with aniline under mild conditions. In addition, trinuclear (type E)and tetranuclear (type F)z inc complexesh avea lso been observed and the examples nicely illustrate how the bridging group impacts the overall coordination mode.…”

“…Hundreds of examples have been reported for mononuclear complexes of type A , for example for Cu, Mn, Ni, Y, Zr, and listing them in here would exceed the limits of this review. In contrast, only one example is known for a type B complex, in which the titanium is eightfold coordinated by two bis(pyrroliminate)s forming a trigonal dodecahedron as reported for the bis(amidinate) complex of type E (see above) . Dinuclear bis(pyrroliminate) compounds have also been reported, and homoleptic type C complexes could be isolated for Ag, Co, Cu Mg, Mn, Ni, Ti, and Zn .…”

“…When three ligand molecules frame two metals, dinuclear complexes of type D are obtained. Examples of titanium and yttrium species have been reported and the titanium complex catalyzes the hydroamination reaction of phenylacetylene with aniline under mild conditions. In addition, trinuclear (type E ) and tetranuclear (type F ) zinc complexes have also been observed and the examples nicely illustrate how the bridging group impacts the overall coordination mode .…”

Titanium Amido- and Imido-Complexes Supported by a Tridentate Pyrrolyl Ligand: Syntheses, Characterisation and Catalytic Activities

“…2 Amongst these, titanium complexes have been proved to be some of the most useful catalysts for the hydroamination of alkynes due to their enhanced stability and improved functional group tolerance. [19][20][21][22][23][24] As a continuation of our efforts on studying the hydroamination of alkynes catalysed by pyrrolyl ligand-chelated titanium compounds, [25][26][27] we are exploring the syntheses and catalytic activities of titanium amido-or imido-complexes chelated by H 2 pmpmi [H 2 pmpmi = (2-pyrrolylmethene)-(2pyrrolylmethyl)imine]. [8][9][10][11][12][13][14] This research has indicated that the ligand chelating to the metal centre plays a key role in controlling the regioselectivity of the hydroamination products.…”

“…In general, anti-Markonikov products are preferentially obtained with titanocene catalysts; [15][16][17][18] in contrast, Markovnikov isomers are formed with pyrrolyl ligands. [19][20][21][22][23][24] As a continuation of our efforts on studying the hydroamination of alkynes catalysed by pyrrolyl ligand-chelated titanium compounds, [25][26][27] we are exploring the syntheses and catalytic activities of titanium amido-or imido-complexes chelated by H 2 pmpmi [H 2 pmpmi = (2-pyrrolylmethene)-(2pyrrolylmethyl)imine]. [28][29] H 2 pmpmi is a tridentate, dianionic pyrrolyl Schiff base ligand, that potentially forms a bisamidocomplex with [Ti(NMe 2 ) 4 ], and provides a straightforward access to titanium imido-complexes.…”