Reactions of Pyridyl‐Functionalized, Chelating λ³‐Phosphinines in the Coordination Environment of Rh^III and Ir^III

Abstract

Rh(III) and Ir(III) complexes based on the λ(3)-P,N hybrid ligand 2-(2'-pyridyl)-4,6-diphenylphosphinine (1) react selectively at the P=C double bond to chiral coordination compounds of the type [(1H⋅OH)Cp*MCl]Cl (2,3), which can be deprotonated with triethylamine to eliminate HCl. By using different bases, the pKa value of the P-OH group could be estimated. Whereas [(1H⋅O)Cp*IrCl] (4) is formed quantitatively upon treatment with NEt3, the corresponding rhodium compound [(1H⋅O)Cp*RhCl] (5) undergoes tautomerization upon formation of the λ(5)σ(4)-phosphinine rhodium(III) complex [(1⋅OH)Cp*RhCl] (6) as confirmed by single-crystal X-ray diffraction. Blocking the acidic P-OH functionality in 3 by introducing a P-OCH3 substituent leads directly to the λ(5)σ(4)-phosphinine iridium(III) complex (8) upon elimination of HCl. These new transformations in the coordination environment of Rh(III) and Ir(III) provide an easy and general access to new transition-metal complexes containing λ(5)σ(4)-phosphinine ligands.

Unexpected Multiple Coordination Modes in Silyl-Bridged Bis(phosphinine) Complexes

“…Phosphinines (the phosphorus analogue of pyridine) are fascinating ligands in coordination chemistry because they contain phosphorus in an unusual, multiply bonded environment. − This gives them unique properties including diagnostic 31 P­{ 1 H} NMR resonances at high chemical shifts in an “aromatic” region and variable binding modes such as η 6 binding − and nondirectional η 1 binding. − Electronically, phosphinines function as π-accepting ligands − but can also function as noninnocent ligands due to facile nucleophilic attack at P under certain conditions. − Monodentate phosphinine ligands − and hybrid ligands, where the phosphinine is connected to another donor, − ,,− are being increasingly explored in coordination chemistry and catalysis; however, ligands based on multiple phosphinine units are much rarer. , Examples include a trans -coordinating diphosphinine, diphosphorus analogue of 2,2′-bipyridine ( A , tmbp: 4,4′,5,5′-tetramethyl-2,2′-biphosphinine, Chart ), ,, and very recent work on multidentate phosphanyl phosphinines . Using a very versatile diazaphosphinine methodology, − Mathey, Le Floch, and co-workers synthesized and studied the coordination chemistry of silyl-substituted multidentate phosphinine ligands with Ir, Rh, , Au, and W­(CO) 3 . , A bis­(phos­phinine) with a SiMe 2 linker and featuring 3,3′-Ph substituents was also synthesized (Chart , B ), and although its reduction chemistry was studied in detail...…”

Au(I)-complexes ligated by hybrid P,S,N-ligands as the efficient catalysts for hydration of phenylacetylene

“…In contrast to monodentate and bidentate phosphines, the hybrid P,X-ligands, which contain significantly different types of hard (X = N-, O-, or/and S-) and soft (P-) donor functions and can develop the possible multiple ligations to the metal center through intramolecular or intermolecular coordination, have represent a very promising class of ligands for transition metal complex catalyzed reactions [26][27][28][29][30]. Such hybrid ligands possess one weakly coordinating group (hard donor) that can reversibly release during the catalytic cycle providing unsaturation at the metal center [31][32][33]. Anyway, the hybrid ligands were rarely used in Au(I)-complex catalyzed hydration.…”

2-(2′-Pyridyl)-4,6-diphenylphosphinine versus 2-(2′-pyridyl)-4,6-diphenylpyridine: synthesis and characterization of novel Cr0, Mo0 and W0 carbonyl complexes containing chelating P,N and N,N ligands

“…[21][22][23][24][25][26][27][28][29][30] Such chelates are intriguing bidentate P,N hybrid ligands, which have recently been explored extensively by our group. 28,[31][32][33][34][35] Substituting nitrogen by phosphorus in similar structures causes rather diverse properties of the resulting compounds due to the electronic difference that exists between these heteroatoms. [23][24][25][26][27][28][34][35][36][37][38][39] As a matter of fact, the electronic properties of phosphinines differ substantially from those of pyridines, as shown by photoelectron and electron transmission spectroscopy as well as by theoretical calculations.…”