Group 9 and 10 Metal Complexes of an Ylide-Substituted Phosphine: Coordination versus Cyclometalation and Oxidative Addition

Abstract

Ylide-substituted phosphines (YPhos) have been shown to be excellent ligands for several transition metal catalyzed reactions. Investigations of the coordination behavior of the YPhos ligand YSPPh2 (1) [with YS = (Ph3P)(SO2Tol)C] toward group 9 and 10 metals revealed a surprisingly diverse coordination chemistry of the ligand. With Ni(CO)4, the formation of a di- as well as tricarbonyl complex is observed depending on the reaction conditions. In [(κP,η2-benzene-1)Ni(CO)2] the phosphine ligand also coordinates via a phosphonium bound phenyl group to the metal leading to a unique nickel η2-arene interaction, which can be viewed as an intermediate state toward P–C bond activation. Full cleavage of the P–C bond takes place with [Rh(COD)Cl]2 leading to a complex salt with [(κP,κO-1)Rh(COD)]+ as cation and a dirhodium trichloride complex anion. Here, YSPPh2 underwent P–C bond cleavage to thus act as an anionic diphosphine ligand. In contrast, in [(κP,κO-1)Rh(COD)]+ as well as [(κP,κO-1)Rh(CO)Cl], formed from the reaction of 1 with [Rh(CO)2Cl]2, the YPhos ligand acts as bidentate ligand complexing the metal via the phosphine and sulfonyl moiety with an intact PPh3 unit. A further type of coordination is observed with [Ir(COD)Cl]2. Here, phosphine coordination is accompanied by C–H activation at one of the phosphonium bound phenyl groups leading to a cyclometalated complex.

Phosphorus‐Containing Superbases: Recent Progress in the Chemistry of Electron‐Abundant Phosphines and Phosphazenes

“…[ 19 , 42 ] During research on ylide and yldiide compounds as ligands in transition metal complexes and the stabilization of reactive low‐valent main group elements, Gessner and co‐workers connected the strongly π‐donating ylidyl groups as substituents to a phosphorus atom and obtained electron‐abundant ylidylphosphines (YPhos). [ 108 , 109 , 110 , 111 , 112 ]…”

“…YPhos ligands in general represent valuable electron‐rich phosphines, which was demonstrated by their readily formation of transition metal complexes, such as gold(I)[ 106 , 111 , 115 ] or palladium[ 112 , 113 , 114 ] complexes, which have been successfully employed as catalysts in amination and hydroamination reactions, as well as alpha arylation with arylchlorides among others. [116]…”

“…[19,42] During research on ylide and yldiide compounds as ligands in transition metal complexes and the stabilization of reactive low-valent main group elements, Gessner and co-workers connected the strongly π-donating ylidyl groups as substituents to a phosphorus atom and obtained electron-abundant ylidylphosphines (YPhos). [108,109,110,111,112] Three simple reaction paths A-C in Scheme 14 were presented to synthesize ylidylphosphines starting from alkylphosphonium salts, which can be easily prepared via reaction of the respective phosphine with alkylhalides (Scheme 14). [113,115] Depending on the nature of Z, double deprotonation with metal bases and subsequent nucleophilic substitution at halophosphines deliver the desired YPhos ligands 34a-e in moderate to high yields of 69-92 % (route A).…”

“…[108,109,114] The resulting ligands in Cy Y Me PCy 2 (34k-m) show elevated stability and a remarkable performance in palladium-catalyzed amination reactions of aryl chlorides at room temperature (Scheme 14). [108,109] YPhos ligands in general represent valuable electron-rich phosphines, which was demonstrated by their readily formation of transition metal complexes, such as gold(I) [106,111,115] or palladium [112][113][114] complexes, which have been successfully employed as catalysts in amination and hydroamination reactions, as well as alpha arylation with arylchlorides among others. [116] Scheme 11.…”

Selective Pd-Catalyzed Monoarylation of Small Primary Alkyl Amines through Backbone-Modification in Ylide-Functionalized Phosphines (YPhos)

“…Recently, our group reported on the use of ylide-substituted phosphines (YPhos) as highly efficient ligands in gold catalysis 12 as well as Pd-catalyzed C—N and C—C coupling reactions. 13 YPhos ligands are, in general, electron-rich phosphines and easy to synthesise in few steps from cheap starting materials.…”