Synthesis and Molecular Structure of trans-Dichlorodi((4-fluorophenyl)-methanamine)palladium(II)

Abstract

The use of palladium complexes to catalyze the coupling of organoboron compounds with aryl or vinyl halides has become one of the most widely used tools in organic synthesis. The scope and utility of the Suzuki–Miyaura reaction has been the subject of several excellent reviews.1 The use of boronic acids in this cross coupling process is especially advantageous as these compounds are relatively nontoxic and thermally, airand moisture-stable.2 Numerous advances have been made to this reaction since its discovery. For instance, the use of aryl chlorides as substrates and the ability to conduct the reaction at low temperature and at low catalyst loading have greatly increased the versatility of the Suzuki–Miyaura cross coupling reaction. Catalyst development has also played a significant role in improving this reaction as traditional palladium complexes used to catalyze this transformation contain airsensitive phosphine ligands. In recent years, a considerable amount of research has also focused on designing new catalysts that can be used to carry out this reaction in alternative solvents.3 We report here on the synthesis and molecular structure of a palladium complex containing fluorinated benzylamines for its potential use in the Suzuki–Miyaura cross-coupling reaction. A suspension of PdCl2 (150 mg, 0.85 mmol) in MeOH (15 mL) was treated with NaCl (100 mg, 1.71 mmol) at RT and stirred for 1 h. A MeOH (2 mL) solution of 4fluorobenzylamine (212 mg, 1.69 mmol) was added dropwise to the reaction mixture and stirred for 1 h resulting in the formation of a yellow precipitate. The solid was collected by suction filtration and washed with MeOH (5 mL) and hexane (10 mL) to afford the title compound. Crystals were obtained by recrystallization from DMSO at RT. Yield: 290 mg (80%); m.p. = 495 – 497 K (decomposition). Spectroscopic NMR data (in DMSO-d6): 1H d: 7.50 (br m, 4H, Ar), 7.14 (br m, 4H, Ar), 3.97 (br s, 4H, CH2), 3.58 (br s, 4H, NH2); 13C{1H} d: 162.0 (d, JC-F = 240 Hz, CF), 135.1, 131.3 (d, JC-F = 8 Hz, Ar), 115.4 (d, JC-F = 21 Hz, Ar), 47.4 (CH2); 19F{1H} d: –115.3. FT-IR (Nujol): 3257, X-ray Structure Analysis Online