Chiral (SO)–N–(SO) Sulfoxide Pincer Complexes of Mg, Rh, and Ir: N–H Activation and Selective Sulfoxide Reduction upon Ligand Coordination

Abstract

Multigram quantities of the optically pure amino−bis-sulfoxide ligand (S,S)-bis(4-tert-butyl-2-(ptolylsulfinyl) phenyl)amine ((S,S)-3) are accessible by in situ lithiation of bis(2-bromo-4-tert-butylphenyl)amine (1) followed by a nucleophilic displacement reaction with Andersen's sulfinate 2. Deprotonation of (S,S)-3 with MgPh2 yields the magnesium amido−bis-sulfoxide salt (S,S)-4 quantitatively. AbstractMulti-gram quantities of the optically pure amino-bissulfoxide ligand (S,S)-bis(4-tert-butyl-2-(ptolylsulfinyl)phenyl)amine ((S,S)-3) are accessible by in situ lithiation of bis-(2-bromo-4-tertbutylphenyl)amine 1 followed by a nucleophilic displacement reaction with Andersen's sulfinate 2.

C2-Symmetric (SO)N(SO) Sulfoxide Pincer Complexes of Mg and Pd: Helicity Switch by AmbidentateS/O-Coordination and Isolation of a Chiral Pd-Sulfenate

“…The S–O bond lengths in 6 (1.509(2)–1.514(2) Å) and in 7 (1.505(4)–1.515(4) Å) are elongated by ca. 0.01 Å when compared to those of their respective free ligands, 4 and 5 (and similar to the distances of the H-bonded S–O functions in meso - 4 and in ( S , S )- 5 ), while the S–C Ar bonds to the backbone (1.774(3)–1.784(2) Å in 6 ; 1.766(5)–1.786(5) Å in 7 ) are contracted by about 0.02 Å. As observed in the H-bonded sulfoxide in meso - 4 , the geometry of the S atoms is flattened upon O -coordination to the Mg­(II) centers (sum of angles around S: 317.5–318.7° in 6 ; 315.61–319.58° in 7 ), mainly through opening of the C Backbone –S–O angles by about 5° when compared to the free ligands.…”

“…The synthesis of the t -butyl substituted ligand ( R , R )- 4 is outlined in Scheme and follows the previously established protocol for the p -tolyl derivative ( S , S )- 5 (see Scheme below) . Halogen-lithium exchange of bis­(2-bromo-4-( t -butyl)­phenylamine ( 1 ) with 3 equiv of BuLi affords sparingly soluble off-white trilithium salt 2 in quantitative isolated yields.…”

“…Chiral sulfoxides have emerged as competent ligands for organocatalysis and metal-catalyzed organic transformations, not the least because effective chiral induction appears to be achieved also through electrostatic effects . In particular, chiral sulfoxide pincer designs prove promising, and in this context, our laboratory is developing new C 2 -symmetric sulfoxide (SO)–N–(SO) pincer architectures . Here we wish to communicate the enantioselective synthesis of a bulky, t -Bu-substituted and electron-rich variant of this ligand type and present our insights into the coordination chemistry of such ligands with magnesium and palladium.…”

Synthesis and Characterization of a Novel Bis‐Sulfoxide and Its Evaluation as a Ligand in p‐Block Chemistry

“…[5,7,[9][10][11][12][13][14][15][16][17][18] In most of the cases the coordination to the metal center is realized through the sulfur atom of the sulfinyl group, [5,11,14,15,[18][19][20][21][22][23] however, coordination through the oxygen atom is also a possibility, some examples are presented in the literature. [12,14,[23][24][25][26] The synthesis of the sulfoxides can be realized by different methods such as the arylation of sulfenate anions by a coupling reaction, a nucleophilic substitution or an electrophilic attack, with the formation of a C-SO bond, [27][28][29][30][31] or by oxidation of a sulfide through a thioether as intermediary derivative. [32][33][34][35][36][37][38][39] wards tin, silicon and phosphorus containing derivatives.…”

“…For example, the bis‐sulfoxide derivatives are used as ligands in the stabilisation of transition metal or lanthanide complexes or as ligand in transition metal‐catalyzed reactions or in various catalytic processes , , . In most of the cases the coordination to the metal center is realized through the sulfur atom of the sulfinyl group,, , , , however, coordination through the oxygen atom is also a possibility, some examples are presented in the literature , , …”