THE SYNTHESES AND VIBRATIONAL-SPECTRA OF TETRAKIS(CARBONYL) PALLADIUM(II) AND PLATINUM(II) UNDECAFLUORODIANTIMONATE(V), [PD(CO)4][SB2F11]2,AND [PT(CO)4][SB2F11]2

The reductive carbonylation of either platinum(IV) fluorosulfate, Pt(S O3F)4, or palladium(III) fluorosulfate, Pd(SO3F)3, either in solution of fluorosulfuric acid, HSO3F, or in the solid state with CO at pressu res of 0.5 to 2 atmospheres and at 25-degrees-C, affords in high yield complexes of the type M(CO)2(SO3F)2, M = Pd or Pt. The square-planar complexes are readily converted by solvolysis in liquid antimony(V) fl uoride in the presence of CO at a pressure of about 1 atmosphere to wh ite, thermally stable, salts of the composition [M(CO)4][Sb2F11]2, M = Pd or Pt, which contain the novel, square-planar cations [Pd(CO)4]2and [Pt(CO)4]2+. The two cations exhibit the highest CO stretching fre quencies reported so far, about 120 cm-1 higher than in free CO, which suggests the absence or near absence of pi-back donation for the M-CO bond.