Complex and Its Platinum Precursor

Albanesi, R. Bemardi, P. Moggi, G. Predieri, and E. Sappa, Gazz. Chim. Ital., 116, 38S (1986). 

NajCPtClJ + (C H5)2PCH2CH2P(C,H5)j —. Pt[(C6H5)2PCH2CH2P(C6H5yCl2 Pt[(CeH5)2PCH2CH2P(CeHs)ja2 + 2Na[Co(CO)4] 

Submitted by K. YASUFUKU, H. NODA, and H. YAMAZAKI Checked by S. MARTINENGO  

Several mixed-metal clusters containing platinum and cobalt are known and some of them have been employed as methanol homologation catalysts. Among them, the title compound was first prepared unambiguously from the reaction of dichloro[l,2-ethanediylbis(diphenylphosphine)]platinum with sodium tetracarbonylcobaltate, Na[CO(CO)4]. The compound also may be prepared by the reaction of [l,2-ethanediylbis(diphenyl-phosphine)]bis(phenylethynyl)platinum with Co2(CO)s.  

The reaction of dichlorobis(triphenylphosphine)platinum(II) with Na[Co(CO)4] gives only the tetrametal cluster, Pt2Co2(PPh3)(CO)g, in a low yield. The corresponding trimetal cluster, PtCo2(PPhj)(CO)8, is obtained 

Sodium tetracarbonylcobaltate(l —) is prepared from Co2(CO)g (0.6 g) and 3% of Na-Hg (15 g) in tetrahydrofuran (THF).8 Dichloro[l,2-ethanediylbis-(diphenylphosphine)]platinum (1.0 g, 1.5 mmol) is suspended in freshly distilled, dry, and oxygen-free THF (20 mL) in a 100-mL two-necked flask fitted with a refluxing condenser, a Teflon-coated magnetic stirring bar, and an inlet for nitrogen connected to a mercury or mineral oil bubbler for venting excess gases. 

---

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. 

In the synthesis of supported platinum catalysts, chloride complexes of platinum (IV) are commonly used as precursors. Their sorption on the alumina surface occurs from aqueous solutions and implies the involvement of OH groups of the support surface. Therewith, two main mechanisms of the interaction between metal complex and support are considered, implementation of each mechanism depending both on the chemical composition of a complex (degree of hydrolysis) and the ratio of various OH groups (Belskaya et al., 2008, 2011 Bourikas, 2006 Lycourghiotis, 2009). The first mechanism consists in the formation of outer sphere complexes it implies electrostatic interaction between chloroplatinate and alumina surface, which is protonated and positively charged at low pH of the solution ... 

A new platinum(O) carbonyl complex has been prepared by the reaction of 3 equiv. of carbon monoxide with a carbene complex (Equation (1)). Not only does the carbon monoxide displace an existing ligand but coordinated GO is also attacked by the ligating nitrogens, with the siloxy group migrating to give the unusual tris-carbene carbonyl complex 1, where all the donor atoms are carbon. Yields are reported to be quantitative, and an X-ray structure has a short Pt-GO bond of 1.868(6) A with a GO stretch of 2,038 cm Further aspects of the synthesis of both 1 and its precursor are discussed in Sections 8.07.3.2.2 and 8.07.3.3. 

Due to its low melting point (30 °C), complex Pt( 7 -GsH4Me)Me3 has been widely employed as a precursor for platinum thin films using both chemical-vapor deposition (CVD) and atomic layer deposition (ALD) techniques. This complex also exhibits high values of absolute photochemical efficiency (cr) (0.34 methylcyclohexane 0.41 -pentane) following excitation at 313 and 366 nm, and even higher in the presence of SiHEts (0.79-0.85), and its efficiency as an effective photoinitiator for hydrosilylation reactions in vinyl/hydride silicone mixtures has been demonstrated. ... 

The platinum precursor species [Pt(T] -CH2=CH2)(PPh3)2], postulated by Smith and Iverson, hold out an inducement since the olefin ligand did not always serve as an innocent mask for the low-valent metal center. In fact, tris(bicyclo[2.2.1]heptene)platinum(0) instantaneously reacts with B2Cat2 at room temperature to give a bis(boryl)bicyclo-[2.2.1]-heptane as the chief organic product (Scheme 8)." It indicated that metal-olefin complexes... 

From this overview it also appears that in most cases, catalytic tests have been performed with catalysts formed in situ from a metal precursor and the desired chiral phosphine, according to usual procedures, while specific catalyst design has been done only sporadically. Relevant examples are the DuPHOS/diene rhodium complexes mentioned in Fig. 10.31 (Sect. 10.3.2) and the platinum/NHC/phos-phine derivatives C4 which allowed highly enantioselective platinum promoted cycloisomerizations to be carried out (Fig. 10.44). 

In the early work on the thermolysis of metal complexes for the synthesis of metal nanoparticles, the precursor carbonyl complex of transition metals, e.g., Co2(CO)8, in organic solvent functions as a metal source of nanoparticles and thermally decomposes in the presence of various polymers to afford polymer-protected metal nanoparticles under relatively mild conditions [1-3]. Particle sizes depend on the kind of polymers, ranging from 5 to >100 nm. The particle size distribution sometimes became wide. Other cobalt, iron [4], nickel [5], rhodium, iridium, rutheniuim, osmium, palladium, and platinum nanoparticles stabilized by polymers have been prepared by similar thermolysis procedures. Besides carbonyl complexes, palladium acetate, palladium acetylacetonate, and platinum acetylac-etonate were also used as a precursor complex in organic solvents like methyl-wo-butylketone [6-9]. These results proposed facile preparative method of metal nanoparticles. However, it may be considered that the size-regulated preparation of metal nanoparticles by thermolysis procedure should be conducted under the limited condition. 

The most important contributions in this area, however, directly related to bond activation chemistry, and, undoubtedly triggered by theoretical considerations along the lines of Figure 1, were reported by Whitesides and coworkers in 1986 and 1988 [11]. It was shown that the bent, bisphosphine-coordinated platinum chelate complex [(dcpe)Pt(O)] (9) (dcpe = bis(dicyclohexylphosphino)ethane), which could be generated thermally as a "hot" reactive intermediate by reductive elimination of neopentane from its ris-neopentylhydride Pt(II) precursor at around 60-70°C in solution, was able to activate C-H bonds, even of unactivated alkanes. 

---