PSb⁺P Ligand: Platform for a Stibenium to Transition-Metal Interaction

Abstract

The coordination chemistry of cationic divalent pnictogen ligands, such as nitrenium and phosphenium, has been well-explored in recent years. However, corresponding studies of a heavier congener, stibenium ion, are rare. To better facilitate a Sb+–metal interaction, a tridentate P-Sb+-P ligand with two phosphine buttresses was designed and synthesized, and its coordination chemistry toward late transition metals was investigated. The stibenium ligand was delivered as an activated P­(SbCl)­P-AgOTf complex (2) that releases AgCl and the P-Sb+-P ligand upon the treatment with transition metals. Reacting 2 with Rh­(I) and Ir­(I) metals yielded the anticipated stibenium–transition-metal complexes [(Rh­(COD)­Cl)2(μ-PSb+P)] OTf ([3]­[OTf]) and [(Ir­(COD)­Cl)2(μ-PSb+P)] OTf ([4]­[OTf]). The M–Sb+–M bridging structure was confirmed by single-crystal X-ray crystallography, and the bonding situation was examined computationally. Theoretical studies revealed the presence of three-center delocalized M–Sb+–M bonding interactions in [3]­[OTf] and [4]­[OTf].

Kinetically Stabilized Diarylpnictogenium Ions

“…[1] Unlike those, pnictogenium ions are also strong electrophiles, which can be attributed to the positive charge that attracts any nucleophile present. Consequently, the vast majority of phosphenium ions, [R 2 P] + , arsenium ions, [R 2 As] + , [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] stibenium ions, [R 2 Sb] + [52][53][54][55][56][57][58][59] and bismuthenium ions, [R 2 Bi] + , [60][61][62][63][64][65][66][67][68][69][70][71][72] reported in the literature are either affected by ion pairing or stabilized by electron-rich ligands or substituents, which inter-or intramolecularly fill the vacant p-orbital. These electronically stabilized pnictogenium ions often have a dramatically reduced Lewis acidity and cannot be regarded as genuine 6 VE species as they fulfill or even exceed the octet rule.…”

Catalyst-Free, Zn-Mediated Decarboxylative Coupling of Chlorostibines to Access Alkylstibines with Stable C(sp3)–Sb Bonds

“…The synthesis of alkylstibines containing at least one C­(sp 3 )–Sb bond has attracted more attention over the past few decades due to their versatile applications. These applications include their use in living radical polymerization, as alkylation reagents, as starting materials for metal–organic chemical vapor deposition, to enhance the magnetic properties of 3d metal centers through ligand effects, and to improve the catalytic properties of metal complexes through co-ligand effects, and the alkylstibines exhibit antitumor activity . Previously, we developed a nickel-catalyzed cross-coupling reaction for C­(sp 3 )–Sb bonds from chlorostibines with alkyl boronic acids and alkyl halides, but the benzylation of organostibines, as well as the construction of C­(sp 3 )–Sb bonds from natural products, drug molecules, and some complex alkyl blocks, remains challenging.…”