Phosphine-metal complexes platinum

Costa, E., Pringle, P.G., Smith, M.B., and Worboys, K., Self-replication of tris(cyanoethyl)phosphine catalyzed by platinum group metal complexes, /. Chem. Soc., Dalton Trans., 4227, 1997. 

While hydrosilylation of 1-alkenes and HSiCl3 with platinum catalysts provides linear products (1-trichlorosilylalkanes), palladium chloride modified with phosphines gives products carrying the trichlorosilyl group at the secondary carbon. This is highly remarkable because all other metal complexes studied so far lead to 1-substituted products. This regioselectivity leads to the possibility to carry out asymmetric hydrosilylation. 

In view of excess phosphine being inhibitory in many catalytic reactions, it is surprising that the hydrophosphination reaction is not suppressed by the phosphines formed. In agreement with this, the product phosphine P(CH2CH2CN)3 is reluctant to form tetrakis(phosphine)platinum species, allowing the metal complex to be coordinatively unsaturated. Likewise, the... 

While today the construction of such bidentate phosphine ligands with the use of an assembly metal is referred to as supramolecular chemistry, this is not to say that there are no examples in older literature utilizing this principle. Actually, there are many and using as a search term hetero bimetallic complexes (a named coined in the early 1980s) leads us to a plethora of complexes. For instance in complex 29, reported by Rauchfuss in 1982, one would consider copper as the assembly metal and platinum as the potential catalytic metal [70]. 

Palladium(I) complexes are in general dimeric or oligomeric and consequently, although they have a d9 configuration, they are usually diamagnetic. The chemistry of this oxidation state is discussed in Section 51.3. Unlike most transition metals, the chemistry of low valent palladium is not dominated by carbonyls [Pd(CO)4] is only stable at 80 K in a matrix. As with platinum, the most common complexes are those containing phosphines, where complexes of the type [PdL ] (n = 2, 4) have been isolated. The chemistry of palladium(O) is dealt with in Section 51.2 and elsewhere.2... 

Several groups have screened a variety of transition metal complexes for activity in the double silylation system, but only compounds of nickel, palladium, and platinum appear to be viable catalysts. The key factor appears to be the involvement of a M(0) species, although certain M(II) complexes can also be used, presumably with in situ reduction to M(0). Generalizations regarding the activity of the different transition metal complexes are difficult, as many variables exist in each system. However, the most active complexes seem to combine palladium metal centers with dba, small basic phosphine, or isocyanate ligands. 

Divalent and tetravalent Pt probably form as many complexes as any other metal. The platinum(II) complexes are numerous with IV. S, halogens, and C. The letranitritoplatinum complexes are soluble in basic solution. Tetranitntoplatinum(II) ion is formed when a solution of plat-inum(II) chloride is boiled, at about neutral pH, with an excess of NaNO f. The ammonium salt may explode when heated. Generally, platinum-metal nitrites should be destroyed in solution. They never should be heated in the dry form. Pladnum(II) complexes most often have a coordination number of 4. Many compounds have been prepared with olefins, cyanides, nitriles, halides, isonitnles, amines, phosphines, arsines, and nitro compounds. 

A reaction mechanism involving the formation of a gold hydride intermediate was tentatively suggested, in analogy with mechanisms known to operate for soluble platinum group metal catalysts such as those of palladium or rhodium phosphine hydride complexes.47... 

Difficulties (41, 42) associated with the use of pentamethyldisilane in hydrosilations catalyzed by usual metal complex catalysts led Yamamoto et al. to study the interaction of penta- and tetramethyldisilanes with transition metal complexes (43). Bis(phosphine)platinum chlorides effectively catalyzed the redistribution in Eq. (66) (R = Me, H). Yamamoto et al. 

The simplest supramolecular bidentate ligand derives from secondary phosphine oxides (SPO). Complexes of transition metals with SPOs have been known for 45 years, and they were introduced as catalysts by van Leeuwen and Roobeek in the early 1980s (66). The complex used first was a platinum hydride containing two SPOs, cormected to one another by a strong hydrogen bond, and a triphenylphosphine to complete the coordination sphere. SPOs have a very strong tendency to occur in pairs connected by hydrogen bonds in many metal complexes they act as bidentate monoanions. 

The coordinative reactivity of phosphine complexes of platinum(O), palladium(O) and nickel(O) Reversible activation of covalent molecules by transition metal complexes. The role of the covalent molecule... 

Tertiary phosphine complexes of the platinum metals Complexes in which the metal has an oxidation state of zero... 

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