No abstract

[reaction: see text] A general new method for the one-pot preparation of secondary phosphines 11 and in situ generation of their borane complexes 12 is described. This method consists of the sequential addition, at room temperature, of equivalent amounts of R(1)MgBr and R(2)MgBr to 1 equiv of the phosphorus atom donor reagent 1. Final treatment with water gives secondary phosphines R(1)R(2)PH (or the corresponding phosphine-borane complexes if treated with BH(3).THF) and the end product 6, which can be recycled.

The reaction of benzothiadiphosphole 1 with an equimolar mixture of R1MgBr and R2MgBr gave intermediate A', which, after only 4-5 min, was treated with an equimolar amount of R3MgBr, giving the asymmetric phosphine PR1R2R3 in 45% overall yield (75-80% yield when R1 = R2 and 85-90% yield when R1 = R2 = R3) and the byproduct 6 in 90% yield. The treatment of 6 with PCl3 quantitatively regenerates the starting reagent 1. Treatment of the phosphines with elemental sulfur gave the corresponding sulfides.

The spontaneous formation of the heteroligated complex [PtCl(κ2‐Ph2PCH2CH2SMe)(Ph2PCH2CH2SPh)]Cl (8 a) by a novel ligand rearrangement process has been observed. By using the weak‐link approach, the relative arrangement of the alkyl and aryl groups can be controlled by abstraction of chloride from 8 a to form the closed complex [Pt(κ2‐Ph2PCH2CH2SMe)(κ2‐Ph2PCH2CH2SPh)][BF4]2 (5) and reopening using halide ions to form semi‐open complexes [PtX(κ2‐Ph2PCH2CH2SMe)(Ph2PCH2CH2SPh)]BF4 (8 b; X=Cl−) and (8 c; X=I−). Analogous procedures using Ph2PCH2CH2SMe and 1,4‐(Ph2PCH2CH2S)2C6H4 lead to heteroligated bimetallic complexes 7 and 9, illustrating that this ligand rearrangement process can be used as a tool for the assembly of complementary metallosupramolecular structures.

The increasing role of organic derivatives of arsenic, antimony, and bismuth in many fields of chemistry is due to their versatility as ligands, [1] their use in materials science [2] and their applications in the pharmacological field. [3] Despite this, few methods of synthesis of triorganoderivatives of these elements have been reported to date and they all involve multi-step procedures giving products in very low overall yields.[4] Moreover, the toxicity of these derivatives requires that their preparation must be carried out with strong attention and adequate precautions in their handling. For these reasons, to find synthetic one-pot procedures that permit the manipulation of these compounds to be minimised represents an interesting challenge.Here we report a very simple synthesis of new arsenic-, antimony-and bismuth-donor reagents and their use in the one-pot synthesis of cyclic arsanes, stibanes and bismutanes, respectively, through a procedure in which the simultaneous formation of three CÀAs, CÀSb or CÀBi bonds is achieved.Recently, we reported [5] (Scheme 1) a new synthesis of tertiary cyclic phosphanes 2 and 3 in 60-70 % yields [5a,b] by addition of a bisA C H T U N G T R E N N U N G (Grignard) reagent and a Grignard reagent to an unusual phosphorus-donor reagent, the benzothiadiphosphole 1 a, [6] called by us a "butterfly reagent" [7] owing to its particular folded structure. At the end of the reaction the starting reagent 1 a was quantitatively regenerated by addition of one equivalent amount of PCl 3 to the end-product 4, which is the remainder of 1 a obtained after quenching the reaction mixture with water (Scheme 1). More recently, we found that tertiary phosphanes are formed spontaneously in the reaction mixture, and that the quantitative regeneration of the reagent 1 a can be accomplished by simple addition of one equivalent amount of PCl 3 to the crude reaction mixture. [8] Taking these findings into consideration, together with the fact that as As, Sb and Bi, belong to the same group of P they could show similar behaviour, we decided to try a transport process for these elements, in order to find a new protocol for obtaining cyclic organoarsanes, organostibanes and organobismutanes, which, to date, have been synthesised with multi-step procedures and in very low overall yields. [9] For this purpose, firstly we tried the synthesis of new heterocycles 1 b-d (Scheme 2), by reaction between compound 4 and AsCl 3 , SbCl 3 , and BiCl 3 , respectively.[10] With this reaction benzothiaphospharsole (1 b), benzothiaphosphastibole (1 c), and benzothiaphosphabismole (1 d; Scheme 2) were isolated in almost quantitative yields (95-98 %) and characterised.It is worth noting that mass spectra of 1 a-d showed the same peak (m/z = 243), originating by the loss from the molecular ion of the fragment PS, AsS, SbS and BiS, respectively. At the same time, the