Trimethyl-and triphenyl-phosphine displace ethylenediamine from its bis (trimethylgold) complex. Thermal decomposition of PPh,AuMe, gives ethane, the gold(1) complex, and finally the tertiary phosphine and gold. Its dipole moment (5.2 D) is a little less than that of PPh,AuMe (5.6 D), indicating more P-Au back-donation.Gold-phosphorus infrared stretching frequencies of several trimethylphosphine complexes fall in the range 347-391 cm.-l. Metal-phosphorus stretching frequencies of halides (PMe,),MX,, (M = Ni, Pd, or Pt; X = C1, Br, or I) fall within an even narrower range, and the absence of trend with atomic weight of the metal indicates increased x-bonding with increase of atomic weight in this series. Gold-chlorine and -bromine frequencies (311-329 and 210-233 crn.-l) for some gold(1) complexes are reported and are compared with the higher frequencies of gold(1n) complexes. Metalchlorine stretching frequencies in trans-complexes are in the ranges 404-408 (Ni), 353-359 (Pd), and 326-339 cm.-l [Pt(11)]. For cis-complexes v(M-Cl) is lower, covers a wider range, and is affected more by the other ligaiids. Both (PMe,) ,PdCl, and (AsMe,) ,PdCl, have cis-structures in the solid state.