Abstract:The industrially important mixture of symand asym-phobanes are separated efficiently by selective protonation of the sym isomer with hydrochloric acid; carbonylation catalysts generated from diphosphanes derived from the separated isomers have quite different activities and product selectivities.Keywords: basicity; hydrocarbonylation; palladium; phosphanes; separation Phobane is a mixture of the sym-and asym-bicyclic secondary phosphines, 9-phosphabicyclo[3.3.1]nonane (1) and 9-phosphabicyclo[4.2.1]nonane (2), formed by the reaction of PH 3 with 1,5-cyclooctadiene [Eq. (1)].[1]The ratio of the isomers in phobane batches varies from ca. 2 : 1 to 3 : 2. ð1ÞDerivatives of 1 and 2 have been known for almost 40 years [1] and have important applications in catalysis, [2 -4] particularly in Co-based hydroformylation of long-chain alkenes.[2] It is known [5] that 1 is more nucleophilic than 2 and it would therefore be expected that phobane-derived ligands would show different coordination chemistry. [4,5] In fact, we have recently shown that the new diphosphine o-C 6 H 4 {CH 2 P(C 8 H 14 )} 2 derived from 1, containing the "bisbi" backbone, forms mononuclear trans chelates with rhodium(I), nickel(II), palladium(II), and platinum(II).[6] Mixtures of isomeric phobanes are used because an economic separation has not been available. [7] We report here a simple, commercially viable [8,9] procedure for the separation of 1 and 2.Scheme 1 illustrates the method of separation. Both phosphines 1 and 2 readily dissolve in concentrated acids but we observed that 1 is significantly more basic than 2. Thus dropwise addition of concentrated HCl to a 1 M solution of 1 and 2 in ether led to selective extraction of 1. 31P{ 1 H} NMR spectroscopy showed that the ethereal phase contained exclusively 2 and the aqueous phase contained a 7 : 1 mixture of protonated 1 and 2. Ether extraction of the aqueous phase gave 2 in > 99% purity. Addition of NaOH to the aqueous phase and extraction of the liberated 1 into ether gave 1 in 78% yield and > 98% purity after sublimation. This selective protonation procedure is forgiving in the sense that too much or too little acid can easily be corrected as the separation is based on reversible equilibria. The separation is conveniently carried out on 30 -40 g scales (see Experimental Section) and has been carried out on a 175 g scale.When 1 Figs. 1 and 2). Both complexes have approximate C 2 symmetry with the PH bonds essentially perpendicular to the coordination plane and in mutually anti orientations.The structure of [PtCl 2 (2) 2 ] shows that the preferred phobane configuration in 2 has the hydrogen atom on P syn to the five-membered ring. A comparison of the COMMUNICATIONS