Platinum carbonyl, structure

The linear CO stretching frequency for the carbonylated platinum colloid while lower than that found for surface bound CO, is in the range reported for the platinum carbonyl clusters [Pt 3 (CO) 6 ] n / sind we find that the carbonylated colloid is easily transformed into the molecular cluster [Pt 12 (CO) 24 ] (10) reaction with water. The cluster was isolated in 50 yield based on platinum content of the precipitate by extraction with tetraethylammonium bromide in methanol from the aluminum hydroxide precipitated when water is added to the aluminoxane solution. The isolation of the platinum carbonyl cluster reveals nothing about the size or structure of the colloidal platinum particles, but merely emphasizes the high reactivity of metals in this highly dispersed state. The cluster isolated is presumably more a reflection of the stability of the [Pt3(CO)6]n family of clusters than a clue to the nuclearity of the colloidal metal particles - in a similar series of experiments with colloidal cobalt with a mean particle size of 20A carbonylation results in the direct formation of Co2(CO)8. 

Chemistry similar to that described above for iridium clusters has also been observed for rhodium clusters. Several authors [16-18] have prepared [Rh6(CO)i6] in NaY zeolite [R1i4(CO)i2] has also been formed [18], and each of these has been decarbonylated with minimal changes in the metal frame, as shown by EXAFS spectroscopy [18]. Thus there appears to be some generality to the method of forming small clusters in zeolite cages by synthesis of stable metal carbonyl precursors followed by decarbonylation. However, the method is limited. Attempts to use it to prepare zeolite-supported platinum clusters that are structurally simple and uniform have apparently not been successfiil. The literature of platinum carbonyl clusters in zeolites is not considered here because it is still contradictory. 

Since the publication of COMC (1995), there have been many new reports of platinum carbonyl complexes. In general, however, the work reported has been incremental and has built on the earlier work. The structure of this section will largely follow that of the previous editions, but with all polynuclear carbonyls considered together. 

The synthesis and structural characterization of a new pyrazolato-bridged platinum carbonyl dimer [(OG)GlPt(/i-pz)(/i-Gl)PtGl(GO)] and its mononuclear precursor //7. r-[PtGl2(GO)(Hpz)] are reported. The mononuclear precursor contains square-planar platinum centers stacked with a Pt-Pt distance of 3.417(0) A, whereas the dimeric complex has nearly linear Pt-Pt chains with the shortest Pt-Pt distances being 3.399(5) and 3.427(5) A. 

The palladium and platinum metals also form carbonyl compounds. Of the expected compounds Pd(CO)4, Pt(CO)4, Ru(CO)5, Os (CO) 5, Mo-(CO)e, and W(CO)6 only Mo(CO)e has been prepared, although some unsaturated ruthenium carbonyls have been prepared. The compounds Pd(CO)2Cl2, Pt(CO)2Cl2, K[PtCOCl3], etc., show the stability of the four dsp2 bonds. It would be interesting to determine whether or not each CO is bonded to two metal atoms in compounds such as [Pt(CO)Cl2]2, whose structure is predicted to be... 

Park S, Wasileski SA, Weaver MJ. 2001. Electrochemical infrared characterization of carbon-supported platinum nanoparticles A benchmark structural comparison with single-crystal electrodes and high-nuclearity carbonyl clusters. J Phys Chem B 105 9719 -9725. 

The great majority of platinum(I) complexes are binuclear with monofunctional or bifunctional bridging groups. However, there is also a series of unsupported dimers with the general structure shown in (12). These are generally stabilized by phosphine, carbonyl, and isocyanide ligands.17 Dimeric hydride complexes can have terminal or bridging hydrides and these are discussed above in Section 6.5.2.1.4. 

The first homoleptic, dinuclear platinum(I) carbonyl complex [Pt2(CO)6]2+ has been prepared by dissolving Pt02 in concentrated sulfuric acid under a CO atmosphere.92,93 The structure is rigid on the NMR time scale at room temperature. DFT studies suggested a staggered structure for the dimer.92,93... 

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