Dibismuthine diphosphine

An alternative preparative route to R2QER acid esters (Q = P, As, Sb, Bi E = S, Se, Te) of interest due to its generally applicability to all the heavier group 15 and 16 elements, is the dismutation reaction between diorganodichalco-genides and tetraorgano-diphosphines, -diarsines, -distibines or -dibismuthines (Equation 17).2... 

In sharp contrast to the intensely studied reactions of dipenteles with transition metal compounds, reactions with group 13 metal compounds are almost unknown. Only two diphosphine-borane bisadducts of Type C ([H3B]2[Me4P2], [H2(Br)B]2[Me4P2]) have been synthesized and structurally characterized65 but no diarsine, distibine or dibismuthine adducts. We, therefore, became interested in the synthesis of such compounds, focusing... 

No diarsines or diphosphines show thermochromic behavior similar to that of the distibines and dibismuthines. For example, in the series of dipnictogen compounds A, B, and C illustrated in Scheme 6, the thermochromic distibines and dibismuthines correspond to nonthermochromic diarsines and diphosphines. Structural data are available to compare the three diarsines 51 (46), 52 (57), and 53 (5S) with the corresponding distibines 22 (25,26), 36 (37), and 30 (22). Diarsines 52 and 53 crystallize in gauche conformations as opposed to the trans-staggered conformation of the distibines. In neither case are there intermolecular As---As contacts shorter than 4 A. However, the lack of conformational correspondence makes any comparison tenuous. 

Diarsines (R2ASASR2) react easily with diphosphines, distibines and dibismuthines (R jMMR j M = P, Sb, Bi) to give equilibrium mixtures containing R2AsMR j (equation 146 3). 

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