The synthesis and characterization of some copper and silver triphenylphosphine complexes of the (carboxylato)trihydroborate derivatives. H3BCO2R-(R=H, CH3, C2H5) are reported. Isolated are stable crystalline complexes of composition (Ph3P)nMH3BCO2R (n=2, 3; M=Cu, R=C2H5, CH3, H; M=Ag, R=C2H5, H). Results of spectral (IR, NMR), osmometric, and conductivity studies are discussed in terms of the molecular structures of the complexes; possible factors influencing the bidentate or monodentate mode of coordination by the anion are set forth. © 1979, American Chemical Society. All rights reserved.