Amido PNP pincer complexes of palladium(II) and platinum(II): Synthesis, structure, and reactivity

• Published in: Applied organometallic chemistry Vol. 35; no. 3
• Main Authors: Huang, Mei‐Hui, Lee, Wei‐Ying, Zou, Xue‐Ru, Lee, Chia‐Chin, Hong, Sheng‐Bo, Liang, Lan‐Chang
• Format: Journal Article
• Language: English
• Published: Chichester Wiley Subscription Services, Inc 01.03.2021
• Subjects: amido PNP pincer; Aromatic compounds; Chemistry; Couplings; Decomposition reactions; High temperature; Hydrogen atoms; Kumada coupling; olefin insertion; Palladium; Platinum; Reagents; Synthesis; Thermal stability; β‐hydrogen elimination
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.6128

The synthesis of a series of divalent palladium and platinum complexes containing amido PNP pincer ligands of the type [N(o‐C6H4PR2)2]− (R = Ph (1a), iPr (1b)) is reported. Metathetical reactions of [1a–b]PdCl or [1a–b]PtCl with a variety of alkyl Grignard reagents or LiHBEt3 in ethereal or arene solutions generate their corresponding alkyl or hydride complexes [1a]PdR1 (R1 = Me, Et, nBu), [1b]PdR1 (R1 = Me, Et, H), [1a]PtR1 (R1 = Me, Et, nBu, nHexyl, H), and [1b]PtR1 (R1 = Me, H). Although these organometallic complexes are all thermally stable, including those containing β‐hydrogen atoms even at elevated temperatures, compounds [1a]PdH and [1b]PtR1 (R1 = Et, nBu, nHexyl) are not isolable due to facile decomposition. The stability and reactivity of these complexes are discussed. The chloro [1a]PdCl is a superior catalyst precursor to [1b]PdCl, [1a]PtCl, and [1b]PtCl in Kumada couplings, affording, for instance, n‐butyl arenes nearly quantitatively. The X‐ray structures of [1b]PtCl, [1b]PtMe, [1b]PdEt, [1a]PtnBu, [1b]PdH, and [1b]PtH are presented. Although the majority of organopalladium and organoplatinum complexes of [N(o‐C6H4PR2)2]− (R = Ph (1a), iPr (1b)) are thermally stable, including alkyls that contain β‐hydrogen atoms at elevated temperatures, [1a]PdH and [1b]PtR1 (R1 = Et, nBu, nHexyl) decompose readily either during synthesis or upon workup. Complex [1a]PdCl outperforms [1b]PdCl, [1a]PtCl, and [1b]PtCl in Kumada couplings, affording, for instance, n‐butyl arenes nearly quantitatively.