Platinum phosphines

Table 3.23 NMR coupling constants for platinum phosphine complexes [155]...

Figure 3.115 (a) Syntheses of organoplatinum phosphine complexes (b) structures of methyl-platinum phosphine complexes. 

Some Pt complexes bearing electron-donating phosphines can also catalyze the hydration of the C=C double bond of acrylonitrile or crotonitrile and yielded P-hy-droxypropionitrile or P-hydroxybutyronitrile respectively besides the corresponding amide (Eq. 6.38) [22, 75], Among the platinum phosphine complexes examined, [Pt(PEt3)3] (26a), carrying less bulky ligands, was the most effective for the hydration of the olefmic bond. The present catalyst system was ineffective for hydration of other olefins, however. 

Table 1 Hydrosilylation of terminal alkynes with platinum-phosphine complexes 0.01 mol%...

The P coordination chemical shifts for both the L2PtX2 and L3PtX2 complexes (Table 10) are related to the free ligand chemical shifts in a fashion analogous to those found for the palladium complexes. Likewise, for platinum phosphole complexes the coordination chemical shifts are less than those found for similar platinum phosphine complexes also indicating some platinum phosphole back donation. 

It is also found (Table 11) that Jpoi is smaller for phosphole complexes than for similar phosphine complexes demonstrating that there is less s-character in the platinum phosphole bond than in the platinum phosphine bond. Since the platinum s-orbital character is probably constant, this signifies less phosphorus s-character in the phosphole... 

Garcia and Maitlis have reported tliat some d " ML 1 4-electron platinum phosphine fragments [PtL ] (L = PEtj, PMcj, Lj - PhjPCHjCHjPPhj dppe) reversibly insert into the C-S bond of thiophenes -T, BT and DBT as well as of some of their methylated derivatives- to yield the corresponding ring-opened products [PtLjlB C.S-Th)], as exemplified in Eq. 4.7 for DBT [38-44]. 

CHs-Halide bond formation is a side reaction in the Shilov methane oxidation process (Scheme 24) [64]. Mechanistic analysis of several catalytic steps by Bercaw and coworkers showed that the formation of the carbon-chlorine bond takes place in parallel to the formation of methanol, often being the major reaction pathway [65]. The reaction most likely involves a nucleophilic attack of the chloride-anion at the coordinated methyl group of the Pt(IV) intermediate [66]. Thus, the overall mechanism is closely related to the organic SN2-type reaction. Further support for such a mechanism operating in Pt(lV) systems came from the Goldberg group which reported the competitive CH3-I and CH3-CH3 reductive elimination reactions in platinum phosphine complexes (Scheme 25) [67, 68]. 

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