Tris(1‐methyl‐imidazol‐2‐yl)phosphane Complexes of Pnictogen, Tetrel, and Triel Cations

Reversing Lewis acidity from bismuth to antimony

Investigations on the boundaries between the neutral and cationic models of (Mesityl)₂EX (E = Sb, Bi and X = Cl^-, OTf^-) have facilitated reversing the Lewis acidity from bismuth to antimony. We use this concept to demonstrate a higher efficiency of (Mesityl)₂SbOTf over (Mesityl)₂BiOTf in the catalytic reduction of phosphine oxides to phosphines. The experiments supported with computations described herein will find use in designing new Lewis acids relevant to catalysis.

Pyramidal Dicationic Ge(II) Complexes with Homoleptic Neutral Pnictine Coordination: A Combined Experimental and Density Functional Theory Study

An unusual series of Ge(II) dicationic species with homoleptic phosphine and arsine coordination, [Ge(L)][OTf]₂, L = 3 × PMe₃, triphos (MeC(CH₂PPh₂)₃), triars (MeC(CH₂AsMe₂)₃), or κ³-tetraphos (P(CH₂CH₂PPh₂)₃) (OTf^- = O₃SCF₃^-) have been prepared by reaction of [GeCl₂(dioxane)] with L and 2 mol equiv of Me₃SiOTf in anhydrous CH₂Cl₂ (or MeCN for L = triars, triphos). X-ray crystal structures are reported for [Ge(PMe₃)₃][OTf]₂, [Ge(triars)][OTf]₂, and [Ge(κ³-tetraphos)][OTf]₂, confirming homoleptic P₃- or As₃-coordination at Ge(II) in each case and with the discrete OTf^- anions providing a charge balance. The Ge-P/As bond lengths are significantly shorter than those in neutral germanium(II) dihalide complexes with diphosphine or diarsine coordination. Solution NMR spectroscopic data indicate that the complexes are labile in solution. Using excess AsMe₃ and [GeCl₂(dioxane)] gives only the neutral product, [Ge(AsMe₂)₂(OTf)₂], the crystal structure of which shows four coordination at Ge(II), via two As donor atoms and an O atom from two κ¹-OTf^- ligands; further weak, long-range intermolecular interactions give a chain polymer. The electronic structure of the [Ge(PMe₃)₃]²⁺ dication has been investigated using density functional theory (DFT) calculations. The computed geometrical parameters for this dication are in good agreement with the experimental X-ray crystallographic values in [Ge(PMe₃)₃][OTf]₂. The results also indicate that the pyramidal arrangement of the [Ge(PMe₃)₃]²⁺ (computed P-Ge-P angle 96.8° at the B3LYP-D3 level) arises from a balance between electronic energy (E_elec) contributions, which favor a lower P-Ge-P angle, and nuclear-nuclear contributions (E_nn), which favor a higher P-Ge-P angle, to the total energy (E_TOT). An Atoms in Molecules (AIM) analysis reveals that one reason why E_elec decreases as the P-Ge-P angle decreases is because of C···H and H···H interactions between atoms on different CH₃ groups. The stability of the [Ge(PMe₃)₃]²⁺ dication is enhanced by the distribution of a significant part of the positive charge on Ge²⁺ to the atomic centers of the PMe₃ ligands. Similar results were obtained for [Ge(AsMe₃)₃][OTf]₂, showing the tris-AsMe₃ complex to be less stable compared to the PMe₃ analogue. Related calculations were also performed for the neutral [Ge(PMe₃)₂(OTf)₂] and [Ge(AsMe₃)₂(OTf)₂] complexes.

Distannabarrelenes with Three Coordinated SnII Atoms

Crystalline 1,4-distannabarrelene compounds [(ADCAr )3 Sn2 ]SnCl3 (3-Ar) (ADCAr ={ArC(NDipp)2 CC}; Dipp=2,6-iPr2 C6 H3 , Ar=Ph or DMP; DMP=4-Me2 NC6 H4 ) derived from anionic dicarbenes Li(ADCAr ) (2-Ar) (Ar=Ph or DMP) have been reported. The cationic moiety of 3-Ar features a barrelene framework with three coordinated SnII atoms at the 1,4-positions, whereas the anionic unit SnCl3 is formally derived from SnCl2 and chloride ion. The all carbon substituted bis-stannylenes 3-Ar have been characterized by NMR spectroscopy and X-ray diffraction. DFT calculations reveal that the HOMO of 3-Ph (ϵ=-6.40 eV) is mainly the lone-pair orbital at the SnII atoms of the barrelene unit. 3-Ar readily react with sulfur and selenium to afford the mixed-valence SnII /SnIV compounds [(ADCAr )3 SnSn(E)](SnCl6 )0.5 (E=S 4-Ar, Ar=Ph or DMP; E=Se 5-Ph).

Onge PBJ, Binder JF, Suter R, Burford N, Macdonald CLB. 2,6-Bis(benzimidazol-2-yl)pyridine complexes of group 14 elements

Variants of the 2,6-bis(benzimidazol-2-yl)pyridine ligand are used to synthesize novel group 14 complexes of germanium and tin. The salts are characterized by X-ray crystallography, NMR, UV-vis, and the Lewis acidity of some examples are probed.

2,6-Bis(benzimidazol-2-yl)pyridines as more electron-rich and sterically accessible alternatives to 2,6-bis(imino)pyridine for group 13 coordination chemistry

2,6-bis(benzimidazol-2-yl)pyridines are more electron-rich yet more sterically open ligands for monovalent and trivalent group 13 elements than bis(imino)pyridines.

Tris(benzoimidazol)amine (L) complexes of pnictogen(iii) and pnictogen(v) cations and assessment of the [LP]3+/[LPF2]3+ redox couple

A series of cationic complexes involving a pnictogen(iii) (Pn = P, As, Sb) centre and the tetradentate ligand tris((1-ethyl-benzoimidazol-2-yl)methyl)amine (BIMEt3) have been synthesized and comprehensively characterized. Oxidation of [P(BIMEt3)]3+ with XeF2 provides access to [PF2(BIMEt3)]3+ representing the first structurally characterized example of a phosphorus(v) centred trication.

Oxidation of a germanium(ii) dication to access cationic germanium(iv) fluorides

Herein we describe the synthesis and characterization of the tris(1-ethyl-benzoimidazol-2-ylmethyl)amine (BIMEt₃ = L) complex of Ge(ii)²⁺ and its oxidation with XeF₂ to access the cationic germanium fluorides [LGeF₂][OTf]₂ and [LGeF(OTf)][OTf]₂.

Synthesis, characterization and mass-spectrometric analysis of [LSn(IV)F4−x]x+ salts [L = tris ((1-ethyl-benzoimidazol-2-yl)methyl)amine, x = 1–4]

A series of cationic tin fluoride complexes has been synthesized by successive fluoride abstraction from SnF₄ with TMSOTf in the presence of the tetradentate nitrogen donor BIMEt₃.