Complexation of N₂, H₂, CO₂, and Ethylene to a T-Shaped Rhodium(I) Core

Abstract

The new rhodium−dinitrogen complex Rh(N2)[HC(CH2CH2P(t-Bu)2)2] (2) was prepared by elimination of HCl with sodium hydride from the hydrido chloride HRh(Cl)[HC(CH2CH2P(t-Bu)2)2] (1). Complex 2 reacts with various small gaseous molecules, giving rise to the new complexes Rh(X)[HC(CH2CH2P(t-Bu)2)2], X = H2 (3), C2H4 (4), CO2 (5). The first 16 electron rhodium−carbon dioxide complex 5 is spectroscopically characterized. All the transformations are reversible in the presence of free nitrogen. The thermodynamic parameters for these equilibria reactions have been evaluated. It is found that at 25 °C formation of the dihydrogen complex 3 is about 1.24 kcal/mol more favorable than formation of its dinitrogen analogue 2, whereas formation of the carbon dioxide (5) and, surprisingly, ethylene (4) complexes is less favorable than 2 by 2.97 and 1.57 kcal/mol, respectively, yielding the ligating ability to the Rh(I) T-shaped core L = H2 > N2 > C2H4 > (CO2). The new hydrido formate HRh(O2CH)[HC(CH2CH2P(t-Bu)2)2] (7) can be obtained either by reaction of the dihydrogen complex 3 with CO2 or from the carbon dioxide complex 5 with hydrogen.

Neutral Tridentate PNP Ligands and Their Hybrid Analogues: Versatile Non‐Innocent Scaffolds for Homogeneous Catalysis

“…[84] As such, they described the facile deprotonation of the PNP backbone at one of the methylene spacers, concomitant with the dearomatization of the pyridine ring, in the absence of CO. [85] Vitagliano and co-workers have shown that the dicationic complex [Pt (12 Ph )] (73) is a suitable starting compound for stoichiometric reactions that involve nucleophilic attack of alcohols or amines onto coordinated alkenes (e.g., ethene). [86,87] In a related study (Scheme 29), they demonstrated that the same complexes can act as catalysts for the codimerization of ethene and internal alkenes (also known as the hydrovinylation reaction).…”

“…[11] Typical examples include frameworks 1-5 ( Figure 1). [12][13][14][15][16][17][18][19][20][21] Reviews on recent developments of these innocent monoanionic tridentate ligand systems, in particular those that carry a central amido functionality, are available. [10,22] Formally neutral tridentate ligand systems have seen a surge in recent decades.…”

Stabile cyclische Carbene und verwandte Spezies jenseits der Diaminocarbene

“…[74] In ganz ähnlicher Weise wurde ein sehr ungewöhnlicher Rhodiumkomplex mit dem sperrigen starren Li [76] und konnten lediglich in situ durch Ligandendissoziation [77] oder Haptizitätswechsel [78] hergestellt werden. Ansonsten gehen diese Komplexe leicht in Chlor-verbrückte Dimere über, selbst beim Vorhandensein zweier sehr sperriger Liganden L. [79] das Chlorid abstrahiert.…”

Neutrale dreizähnige PNP‐Liganden und deren Hybrid‐Analoga: vielseitige Liganden für die kooperative homogene Katalyse

“…[84] Sie beobachteten die Deprotonierung des PNP-Rückgrats an einer der Methylengruppen, die mit der Desaromatisierung des Pyridinrings einhergeht, in Abwesenheit von CO. [85] Vitagliano und Mitarbeiter haben gezeigt, dass der dikationische [Pt (12 Ph )]-Komplex 73 für stöchiometrische Reaktionen geeignet ist, bei denen Alkohole oder Amine nucleophil mit koordinierten Alkenen reagieren (z. B. mit Ethen).…”