Structural relationships between o-, m- and p-tolyl substituted R3EI2 (E = As, P) and [(R3E)AuX] (E = As, P; X = Cl, Br, I)

Abstract

The compounds R 3 EI 2 (R ¼ o-tolyl, E ¼ As, 1a; R ¼ m-tolyl, E ¼ P 1c; R ¼ p-tolyl, E ¼ As, 1d, P, 1e), which display the charge transfer spoke structure, and [(o-tolyl 3 As)AuCl] 2 have been synthesised and their solid state structures compared to the related complexes, Va; Br, VI; I, VII) on the basis of a similarity of their molecular shape and volume. All of the new compounds 1a, 1c-1e and 2 have been fully spectroscopically characterised and by single crystal X-ray crystallography. The sterically demanding exo 3 o-tolyl ring conformation is observed for 1a, which is comparable to that reported for o-tolyl 3 PI 2 1b, with a long As-I bond 2.7351( 14)A and short I/I distance 2.9528(11) A. The exo 3 o-tolyl ring conformation is maintained on complexation to gold(I) in 2, but has no significant impact on the expected bond lengths, with As-Au 2.3443(15)A and Au-Cl 2.284(4) A. The exo 3 conformation appears to be stabilised in both cases by the formation of a six-fold edge-to-face (EF) 6 embrace. It is found that in some cases the structures of the dihalogen adducts and the gold(I) complexes are isomorphous indicating that ligand packing requirements are most significant i.e. for 1c and IV. Where the structures digress this is due either to the greater ability of the dihalogen adduct to engage in hydrogen bonding 1a, b and I-III; or subtle changes in the nature of the tolyl ring embraces 1d, e and V-VII. Subtle changes in the nature of the tolyl ring embraces also account for the different polymorphs I and Ia and V and Va. There is no credible evidence to suggest that the aurophilic contact, seen in only one polymorph Va, exerts any influence on the overall crystal packing. The structural comparisons presented here add further to the applicability of the recently recognised structural mimicking ability of the R 3 PX 2 systems and [R 3 PAuX] complexes, and that the aurophilic contact is a poor supramolecular synthon.

Alternative Motifs for Halogen Bonding

“…In addition to the above‐mentioned common acceptors, phosphorus, arsenic and tellurium can also act as acceptors for X–X ··· A interactions. Ten substituted triphenylphosphanes forming linear I–I ··· P contacts were reported by Barnes et al32 The I ··· P and I–I distances are similar in all the structures with I ··· P distances of 2.45–2.51 Å (34–35 % reduction, VUNVIK,32a WAJTUY, WAJWEK,32b RARWIS, RARWOY, RARWUE, RARXAL, RARXEP, RARXEP01 and RARXOZ32c) and extremely long I–I distances of 3.08–3.26 Å. This indicates the strong electron‐donating and halogen‐bond‐accepting potential of P, which is also seen from the smaller I ··· P distances in comparison with the vdW radii of the corresponding atoms and relative to the DABCO ··· I 2 reduction.…”

On the Redox Reactivity of a Geometrically Constrained Phosphorus(III) Compound

“…[22] Furthermore, to the best of our knowledge, 4 represents the first structurally characterised example of ap hosphorus(V) diiodide with other species of the formula R 3 PI 2 shown to exist as either phosphoniumi odides or "spoke" charge-transfer adducts. [23] It is noteworthy that the extremelyu pfield 31 PNMR chemicals hift associated with 4 suggests that the five-coordinate structure persists in solution.E xamples of phosphorus(V) monoiodides are also scarce, again requiring arylimino moieties. [24] These observations evidencet he low oxidation potential of 1,s upportingt he facility of small molecule activation at the phosphorus(III) centre.…”

Buchwald‐Type Ligands on Gold(I) Catalysis

“…The structure of the As-based dialkyl-biphenyl gold(I) complexes are in line with what already reported for other As based gold(I) complexes. [100][101][102] Compared to the phosphorous analogous, the AuÀ Cl or AuÀ N distance is shorter, in line with the expected increased electrophilicity of the complexes. In the attempt of synthesizing the cationic gold(I) π-complexes with simple alkenes starting from complex 87, we isolated quantitatively complexes 88 and 89, in which the double bonds of the original alkenes have undergone migration (Scheme 16).…”