The First Cycloaddition Reactions of Dimeric Arsenium Cations

Synthesis, Characterisation and Properties of As‐Monohalogenated Dibenzoarsocines S(C6H4S)2AsHal (Hal = Cl, Br, I) – A Study of the Transannular Interaction S→As

“…[4] Treatment of S(C 6 H 4 SH) 2 with AsCl 3 in benzene yielded S(C 6 H 4 S) 2 AsCl (1) as colourless crystals (see Scheme 2). S(C 6 H 4 S) 2 AsBr (2) and S(C 6 H 4 S) 2 AsI (3) were obtained from a halogen-exchange reaction as reported for antimony complexes [3] between 1 and an excess of KBr/HBr or KI in hot benzene, respectively, yielding colourless crystals for 2 and pale yellow crystals for 3 (see Experimental Section for details).…”

“…The ligand S(C 6 H 4 SH) 2 was prepared according to a reported method. [4] Treatment of S(C 6 H 4 SH) 2 with AsCl 3 in benzene yielded S(C 6 H 4 S) 2 AsCl (1) as colourless crystals (see Scheme 2).…”

“…In 1 and 2 the molecular ion was observed as a low-intensity peak with the appropriate isotopic ratio; for 3 the molecular ion was not observed. In all cases the intense ion fragment in m/z = 323 is assigned to the loss of the halogen atom in the compounds, yielding an S(C 6 H 4 S) 2 As tricyclic moiety, confirming the binding of arsenic to sulfur atoms and the stability of the dibenzotrithiarsocine system. In all the spectra there are peaks corresponding to the S(C 6 H 4 S) 2 , S(C 6 H 4 )S and S(C 6 H 4 ) 2 fragments.…”

“…Some of these ligands, in particular D(CH 2 -CH 2 S) 2 2-with the donor atom D = O, S and NR, are quite flexible and led to the atom A expanding its coordination number through an intramolecular transannular interaction DǞA. In these metallocanes, the conformational diversity is very large.…”

“…In some cases it is very strong; for example in arsocanes the cross-ring bond has been claimed as being responsible for the stabilisation of discrete arsenium cations. [2] On the other hand, the more constrained ligands of type I (Scheme 1) have been explored for several groups in the coordination chemistry of transitional metals as well as light p-block elements; in these type II complexes the transannular interaction can also take place. [3] In particular, we have studied some Sb-monohalogenated dibenzometallocines and we have shown by means of X-ray crystallographic and DFT studies the acidic behaviour of the antimony atom acting as a Lewis acceptor toward sulfur in the decreasing order I Ͼ Br Ͼ Cl.…”