Unsymmetric Dinuclear Rh I 2 and Rh I Rh III Complexes Supported by Tetraphosphine Ligands and Their Reactivity of Oxidative Protonation and Reductive Dechlorination

• Published in: Inorganic chemistry 2022-01, Vol.61 (2), p.1102-1117
• Main Authors: Nakajima, Takayuki, Maeda, Mami, Matsui, Aya, Nishigaki, Mariko, Kotani, Momoko, Tanase, Tomoaki
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c03278

Two linear tetradentate phosphine ligands, -Ph PCH P(Ph)CH CH P(Ph)CH PPh ( = CH ( -dpmppp), NBn ( -dpmppmNBn; Bn = benzyl)) were utilized to synthesize unsymmetrical dinuclear Rh complexes, [Rh Cl ( -dpmppp)(L)] (L = XylNC ( ), CO ( )) and [Rh Cl ( -dpmppmNBn)(L)] (L = XylNC ( ), CO ( )), where electron-deficient Rh → Rh centers with 30 valence electrons are supported by a tetraphosphine in an unusual / - coordination mode. The Rh dimers of - were treated with HCl under air to afford the Rh → Rh dimers with 32 e , [Rh Cl ( -dpmppp)(L)] (L = XylNC ( ), CO ( )) and [Rh Cl ( -dpmppmNBn)(L)] (L = XylNC ( ), CO ( )), via intermediate hydride complexes, [{RhCl (μ-H)RhCl(L)}( -dpmppp)] (L = XylNC ( ), CO ( )) and [{RhCl (μ-H)RhCl(L)}( -dpmppmNBn)] (L = XylNC ( ), CO ( )), and [{Rh(H)Cl (μ-Cl)Rh(L)} -dpmppp)] (L = XylNC ( ), CO ( )) and [{Rh(H)Cl (μ-Cl)Rh(L)} -dpmppmNBn)] (L = XylNC ( ), CO ( )). The hydride intermediates and were monitored under nitrogen by H{ P} and P{ H} NMR techniques to reveal two reaction pathways depending on the terminal auxiliary ligand L. Further, the reductive dechlorination converting Rh Rh ( , ) to Rh ( , ) was accomplished with a CO terminal ligand by reacting with various amines that acted as one-electron reducing agents through an inner-sphere electron transfer mechanism. DFT calculations were performed to elucidate the electronic structures of - and - and to estimate the structures of the hydride intermediate complexes and .