Bulky bis-guanidine ligand-based neutral and cationic zinc alkyl, halide, and hydride complexes: synthesis, characterization, and catalytic application
Source
Dalton Transactions
ISSN
14779226
Date Issued
2025-01-01
Author(s)
Sahoo, Rajata Kumar
Mukhopadhyay, Sayantan
Rajput, Sagrika
Jana, Achintya
Nembenna, Sharanappa
Abstract
The tetra-aryl substituted bis-guanidine ligand L(3H) (L(3H) = {(ArHN)(ArNH)-CvN-C=(NAr)(NHAr)}, Ar = 2,6-<sup>i</sup>Pr<inf>2</inf>-C<inf>6</inf>H<inf>3</inf>) was used for the synthesis of mononuclear zinc(II) alkyl [L(2H)ZnR, R = Me (Zn-1), Et (Zn-2)], iodide [L(2H)ZnI, (Zn-3)], and hydride [L(2H)ZnH, (Zn-4)] complexes. Moreover, the reactions of Zn-1, Zn-2, and Zn-3 with [PhNMe<inf>2</inf>H]<sup>+</sup> [B(C<inf>6</inf>F<inf>5</inf>)<inf>4</inf>]<sup>−</sup> yielded the biguanide zinc alkyl [L(3H)ZnR]<sup>+</sup> [B(C<inf>6</inf>F<inf>5</inf>)<inf>4</inf>]<sup>−</sup> (R = Me (Zn-5), Et (Zn-6)) and iodide [L(3H)ZnI]<sup>+</sup> [B(C<inf>6</inf>F<inf>5</inf>)<inf>4</inf>]<sup>−</sup> (Zn-7) cationic compounds in good yields. All newly isolated and thermally stable zinc complexes (Zn-1-Zn-7) were well characterized by multinuclear NMR (<sup>1</sup>H, <sup>13</sup>C{<sup>1</sup>H}, with additional <sup>11</sup>B and <sup>19</sup>F{<sup>1</sup>H} for Zn-5-Zn-7), HRMS, and single crystal X-ray diffraction studies. Moreover, the well-defined zinc iodide cation (Zn-7) [L(3H)ZnI]<sup>+</sup> [B(C<inf>6</inf>F<inf>5</inf>)<inf>4</inf>]<sup>−</sup> was further used as a catalyst for the synthesis of cyanohydrin enol ether products (RCR’CNOSiMe<inf>3</inf>) by TMSCN addition to carbonyl compounds (RCOR’, R’ = alkyl/aryl) under mild reaction conditions.