The efficient synthesis of chiral or achiral tertiary phosphines bearing an o-bromo (or iodo)aryl substituent is described. The key step of this synthesis is based on the reaction of a secondary phosphine borane with the 1,2-dibromo (or diiodo)arene, owing to the formation in situ of an aryne species in the presence of n-butyllithium. When P-chirogenic secondary phosphine boranes were used, the corresponding o-halogeno-arylphosphine boranes were obtained without racemization in moderate to good yields and with ee up to 99%. The stereochemistry of the reaction, with complete retention of the configuration at the P atom, has been established by X-ray structures of P-chirogenic o-halogenophenyl phosphine borane complexes. The decomplexation of the borane was easily achieved without racemization using DABCO to obtain the free o-halogeno-arylphosphines in high yields.

The first dibenzophospholyl(diphenylphosphino)methane-borane hybrid ligand has been prepared from a Pd-catalyzed reaction of (chloromethyl)diphenylphosphine-borane with the dibenzophospholyl anion. This borane precursor is readily synthesized using a promising new reaction of diphenylphosphine-borane with dichloromethane, under phase transfer catalysis (PTC) conditions. The dibenzophospholyl(diphenylphosphino)methane-borane acts as a chelating P-(η 2 -BH 3 ) ligand to afford an air-stable Rh(I) complex. The X-ray crystal structure of this complex shows complexation of both benzophospholyl and borane moieties.