Establishing the Coordination Chemistry of Antimony(V) Cations: Systematic Assessment of Ph₄Sb(OTf) and Ph₃Sb(OTf)₂ as Lewis Acceptors

Abstract

The coordination chemistry of the stiboranes Ph4 Sb(OTf) (1 a, OTf = OSO2 CF3 ) and Ph3 Sb(OTf)2 (3) with Lewis bases has been investigated. The significant steric encumbrance of the Sb center in 1 a precludes interaction with most ligands, but the relatively low steric demands of 4-methylpyridine-N-oxide (OPyrMe) and OPMe3 enabled the characterization of [Ph4 Sb(OPyrMe)][OTf] (2 a) and [Ph4 Sb(OPMe3 )][OTf] (2 b), rare examples of structurally characterized complexes of stibonium acceptors. In contrast, 3 was found to engage a variety of Lewis bases, forming stable isolable complexes of the form [Ph3 Sb(donor)2 ][OTf]2 [donor=OPMe3 (6 a), OPCy3 (6 b, Cy=cyclohexyl), OPPh3 (6 c), OPyrMe (6 d)], [Ph3 Sb(dmap)2 (OTf)][OTf] (6 e, dmap=4-(dimethylamino)pyridine) and [Ph3 Sb(donor)(OTf)][OTf] [donor=1,10-phenanthroline (7 a) or 2,2'-bipy (7 b, bipy=bipyridine)]. These compounds exhibit significant structural diversity in the solid-state, and undergo ligand exchange reactions in line with their assignment as coordination complexes. Compound 3 did not form stable complexes with phosphine donors, with reactions instead leading to redox processes yielding SbPh3 and products of phosphine oxidation.

Complexes of Stiboranium Mono‐, Di‐, and Trications

“…Signals corresponding to chlorobenzene were observed in the 13 CNMR spectrumo ft he reaction mixture, indicating that reduction of Sb V to Sb III is associated with the oxidative coupling of Ph and Cl. [6,14,15] The redox behavior of Ph 2 SbCl 3 in the presence of bipy and TMSOTf contrasts the apparent redox stability of the previously reported [Ph 3 Sb(bipy)][OTf] 2 , [6,7] whichc ontains af ormald ication. [12,13] Moreover, cationic phosphinec omplexes of Sb III and Sb V centers have been observed to oxidatively couple R 3 Pt of orm diphosphonium cations (R = Me, Et, Pr).…”

“…Although p-blockc enters classically behavea sL ewis donors, exampleso fc ompounds containing p-block centers as Lewis acceptors have been developed only in recent years by introducing ac ationic charge on the p-blockc enter. [6][7][8] Recognizing the potential to enhance reactivity at the Lewis acceptors ite with the presence of ah igher cationic charge, we envisage complexes of the generic formulae [R 2 SbL 3 ] 3 + , [RSbL 4 ] 4 + ,a nd [SbL 5 ] 5 + through the sequential abstraction of halide substituents from X 3 SbR 2 ,X 4 SbR, and X 5 Sb,r espectively,[a] C.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi. Complexeso fa ntimony represent the most diverse series, [2] including examples of mono-, [3] di-, [4] and tri- [5] cations featuring Sb III .C omplexes featuring Sb V as the Lewis acceptor center have been reported for cations of the general formulae [Ph 4 SbL] + and [Ph 3 SbL 2 ] 2 + ,i nw hich L = 4-dimethylaminopyridine, Ph 3 PO, or 4-methylpyridine-N-oxide( OPyrMe).…”

Fluorinated antimony(v) derivatives: strong Lewis acidic properties and application to the complexation of formaldehyde in aqueous solutions

“…The antimony atom is bound to the phosphine oxide with an average Sb–O distance of 2.110(4) Å, which is only slightly longer than the value expected for a typical single bond (∑ CR (Sb,O) = 2.03 Å). 52 Surprisingly, this distance is much shorter than the reported distance in the monocation [(Et 3 PO)SbPh 4 ] + (2.406(2) Å), and essentially identical to the Sb–O distances in the dication [(Et 3 PO) 2 SbPh 3 ] 2+ (2.089(3) Å), 23 thus pointing to a considerable Lewis acidic character for 2 . In the 31 P NMR spectrum, the sharpness and location of the resonance of the Et 3 PO· 2 adduct remained unaffected by the presence of excess Et 3 PO base, in either chloroform (73.5 ppm) or acetonitrile (77.3 ppm).…”

“…20 Inspired by these advances and using fluoride anion affinity data as a guide, 21,22 several groups have paid a renewed attention to the properties of antimony( v ) compounds. 23–26 As part of our contribution to this area, 27–30 we were drawn by the properties of simple neutral derivatives such as triaryl-catecholato-stiboranes ( A , Fig. 1) which have been previously shown to form adducts with Lewis basic substrates.…”

Reversible Oxidative Se−Se Coupling of Phosphine Selenides by Ph3Sb(OTf)2

“…[7] We have now discovered that in an analogousr eaction Ph 3 Sb(OTf) 2 effects oxidative SeÀSe coupling of trialkylphosphine selenides to give salts of 2 (Scheme1c). 31 P{ 1 H} NMR spectra of the respective reaction mixtures indicate that these reactions proceed via the coordination complexes 1(R 3 PSe) (Scheme 1c).…”