Water-soluble phosphines -: Part XII.: Pd catalyzed P-C coupling reactions:: a novel synthetic route to cationic phosphines with para- and meta-guanidiniumphenyl moieties

Mono- and bifunctional guanidinium phosphines (3c, 4a, 4b, 5a-5d, 5f containing para-and meta-guanidiniumphenyl moieties -C6H4-NH-C(NH2)(NR2)(+) (R = H, Me) are accessible in high yields by Pd catalyzed P-C coupling reactions between iodophenyl guanidines I-C6H4-NH-C(NH)NR2 (meta-, para-isomers; R = H, Me) and phenyl- or diphenylphosphine. The X-ray structure of 3c . MeOH (space group P2(1)2(1)2(1)) has been determined, showing a planar guanidinium group in a NH-O and NH-Cl hydrogen bridged arrangement. Pd(II) and Mo(0) complexes of 5c have been synthesized. The influence of the cationic guanidinium group on the electronic and steric parameters of 5c is discussed. A comparative study of 5c, phosphonated and sulfonated phosphine ligands in the biphasic Pd catalyzed Suzuki-type coupling between m-bromophenyldiphenyl phosphine oxide and para-tolyl-boronic acid shows 5c to be less active than Ph2P-C6H4-4-PO3Na2. (C) 2000 Published by Elsevier Science S.A. All rights reserved.