A modular synthesis of tris(aryl)tren ligands: Synthesis, structure and lithiation chemistry

Abstract

A modular synthesis of tris(aryl)tren ligands has been demonstrated via the condensation of nitrilotracetyl chloride with different anilines followed by reduction. Varying the aniline in the condensation step from 2-methylthioaniline, to 2-phenylthioaniline, to 2-chloroaniline, generates 2,2',2"-nitrilotris(N-(2-(methylthio)phenyl)acetamide (1), 2,2',2"-nitrilotris(N-(2-(phenylthio)phenyl)acetamide (2) and 2,2',2"-nitrilotris(N-2-chlorophenyl)acetamide (3) respectively. The 2-chloroaniline synthesis is complicated by the production of N-(2chlorophenyl)-3,5-dioxo-1-piperazine-N-(2-chlorophenyl)acetamide (4), but can be adjusted to produce only 3. The reduction of complexes 1-3 proceeds with lithium aluminum hydride for 1 and 2 and with borane for 3 to yield the tris(aryl)tren ligands tris-(2-(2-(methylthio)phenylamino)ethyl)amine (5), tris-(2-(2-(phenylthio)phenylamino)ethyl)amine (6), and tris-(2-(2-chlorophenylamino)ethyl)amine (7). All three of these ligands can be deprotonated with tert-butyllithium for 5 and 7, and n-butyllithium for 6 to generate their trilithium complexes, 8, 9 and 10 for 5, 6 and 7 respectively, with 10 forming two different solvates (10a and 10b). All complexes are characterized by 1 H and 13 C NMR and the solid state structures of complexes 2, 3, 4, 7, 8, 9, 10a and 10b are described.

A Synthetic, Structural, Spectroscopic, and Computational Study of Alkali Metal–Thioether, −Selenoether, and −Telluroether Interactions

“…The AS 2 Ph2 ligand backbone is bent away from the Li 2 N 2 core of the dimer, with a ligand backbone bend angle of 39° (defined as the angle between the planes of the two acridanide aryl rings). The Li–S distances of 2.494(4) and 2.497(4) Å in 3 are comparable to the Li–S distances found in Power’s complexes [Li 2 Cu 2 Ph 4 (SMe 2 ) 3 ], [Li 3 (CuPh 2 )­(CuPh 3 )­(SMe 2 ) 4 ], [Li 5 (CuPh 2 ) 3 (CuPh 3 )­(SMe 2 ) 4 ], and [Li 4 Ph 4 (SMe 2 ) 4 ] (2.445(9)-2.635(4) Å), and to those for the four-coordinate amido-bridged lithium centers in the 2-(phenylthiol)­phenyl­(tren) (tren = tris­{2-aminoethyl}­amine) thioether complex [Li 3 {N­(CH 2 CH 2 N­(C 6 H 4 SPh-2) 3 }­(THF) 2 ] (2.510(6) and 2.542(6) Å) . The geometry of the sulfur atoms in 3 is pyramidal, with the sum of the C–S–C and C–S–Li angles equal to 294.8(2) and 299.1(2)°.…”

“…Neutral oxa-thia macrocycles such as 1,4,10,13-tetraoxa-7,16-dithiacyclooctadecane ([18]­aneO 4 S 2 ) and/or 1,10-dioxa-4,7,13,16-tetrathiacyclooctadecane ([18]­aneO 2 S 4 ) have been used to access a series of Li, Na, K, Rb, and Cs complexes featuring M–SR 2 linkages. − Additionally, [Na([24]­aneS 8 )]­[B­{C 6 H 3 (CF 3 ) 2 -3,5} 4 ] ([24]­aneS 8 = 1,4,7,10,13,16,19,22-octathiacyclotetracosane), which features an octadentate thiacrown, is unique as it is the only s-block complex in which the metal is coordinated exclusively to thioether donors . Other alkali metal thioether complexes feature more complex multidentate ligands, including thiacalixarenes, − and acyclic ligands containing a mixture of anionic (e.g., R 3 C – , R 2 N – , RO – ) donors and thioether groups. − …”

“…Li 3 {N(CH 2 CH 2 N(C 6 H 4 SPh-2) 3 }(THF) 2 ] (2.510(6) and 2.542(6) Å) 21. The geometry of the sulfur atoms in 3 is pyramidal, with the sum of the C−S−C and C−S−Li angles equal to 294.8(2) and 299.1(2)°.…”