2-(2′-Pyridyl)-4,6-diphenylphosphinine versus 2-(2′-pyridyl)-4,6-diphenylpyridine: an evaluation of their coordination chemistry towards Rh(i)

PdII and PtII Complexes of 2‐(2′‐Pyridyl)‐4,6‐diphenylphosphinine: Synthesis, Structure, and Reactivity

“…In fact, this compound is highly stable towards nucleophilic attack. In the Rh I complex [Rh(1)A C H T U N G T R E N N U N G (cod)]BF 4 [15] the corresponding value is 105.258, whereas in the Ru II complex [21] (tmbp = tetramethylbisphosphinine) it is 106.088. Interestingly, the latter compound is much less stable towards nucleophilic attack, which indicates the disruption of aromaticity upon coordination to a more electrophilic metal center.…”

“…[11][12][13] It turned out that 2-(2'-pyridyl)-4,6-diphenylphosphinine (1, Scheme 1) is readily available from the corresponding pyridyl-functionalized pyrylium salt and PA C H T U N G T R E N N U N G (SiMe 3 ) 3 and we have recently investigated its coordination chemistry with Rh I . [14,15] We anticipated that the additional phenyl group at the 6-position of the heterocyclic framework might lead to a kinetic stabilization of the corresponding metal complexes as the P = C double bond is sterically more shielded for addition reactions. In combination with the chelate effect of the P,N hybrid ligand, this would allow the preparation and isolation of complexes with metal centers even in higher oxidation states.…”

Recent Developments in the Chemistry of Pyridyl-functionalized, Low-coordinate Phosphorus Heterocycles

“…As observed before in related transition-metal complexes of the unsubstituted P,N-ligand 5, the metal center is not located in the ideal axis of the phosphorus lone pair and is clearly shifted toward the nitrogen atom ( Figure 14). 15 Coordination compounds 19a19d were further investigated by means of IR spectroscopy. Interestingly, the electronic properties of such pyridyl-substituted 2,4,6-triarylphosphinine derivatives can indeed be modulated systematically and rather efficiently by introducing substituents into specific positions of the heterocyclic framework.…”

“…The HOMO of 2-(2¤-pyridyl)phosphinine contributes to σ donation from the phosphorus atom toward a metal-centered d orbital, while the HOMO¹3 represents the lone pairs at the heteroatoms for participation in σ bonding with a metal center. 15 The pronounced spherical character and larger coefficient of the phosphorus lone pair compared to that of nitrogen reflects its less directional and more diffuse nature. In 2,2¤-bipyridine, the order of these frontier orbitals is reversed, indicating the rather good σ-donor properties of this ligand.…”

Reactions of Pyridyl‐Functionalized, Chelating λ3‐Phosphinines in the Coordination Environment of RhIII and IrIII

“…[4] We have recently developed a facile synthetic route to 2-(2'-pyridyl)-4,6-diphenylphosphinine (1, Figure 1), which is readily available from the corresponding pyridyl-functionalized pyrylium salt. [5][6][7] It is by now well established that the coordination chemistry of phosphorus-analogues of 2,2'-bipyridines is markedly different from that of classical tertiary diphosphines or their all-nitrogen-counterparts. [8][9][10][11][12] In contrast to (bi)pyridines, phosphinine-based ligands are especially suitable for the stabilization of electron-rich metal centers due to the pronounced p-acceptor properties of the aromatic phosphorus heterocycle.…”