Platinum trialkylphosphines

Caution. All zero-valent platinum compounds and trialkylphosphines employed here are extremely air sensitive and should be handled in a dry nitrogen or argon atmosphere. The trialkylphosphines are malodorous and toxic, and should be handled with care, in a well-ventilated hood. All solvents should be dried (except ethanolj and distilled under nitrogen. 

Heretofore, the most common method for the preparation of the useful platinum(II) complexes of the type [PtCl2L3], where L is a tertiary phosphine, consisted of the reaction between potassium tetrachloroplatinate(II) and tertiary phosphines.1 When trialkylphosphines are used, the reaction usually leads to a mixture of cis- and trans isomers,2 3 and when triaiylphosphines are employed4 only the cis isomers are obtained. The preparation of pure trans complexes by a simple, convenient procedure is highly desirable. 

Figure 4. Graph of Pt-P length (shown with standard deviation limits) against 2]pt-p for platinum(II) complexes of trialkylphosphines , phosphorus trans to phosphorus , phosphorus trans to chlorine , phosphorus trans to other donor atoms O, trans-[Ptl2(PCy3)2], For discussion see Ref. 23 the point with JPt-P > 5000 Hz is for [Pt2(p-Cl)2(COEt)2(PMe2Ph)2] (24). Some platinum(IV) complexes have been...

Splitting of a Water Molecule by Trialkylphosphine Complexes of Platinum and Rhodium and Its Chemical Applications... 

On the other hand, the reaction of 1,2,3-selenadiazole 166 with 1 equiv of Pt(PPh3)4 in toluene at 140 °C (3 h) led to the formation of new selenoplatinum complex 52 in 35% yield (Equation 13) <2005TL1001>. This reaction may involve the insertion of di(triphenylphosphino)platinum into the selenadiazole ring, followed by 1,3-dipolar addition of an intermediate formed in situ by thermal elimination of dinitrogen with the elimination of triphenylphosphine, similar to the reaction with [Pd2(dba)3] and trialkylphosphine described above. The structure of complex 52 was established by X-ray analysis. Complex 52 is a selective catalyst for the hydrosilylation of terminal alkynes. 

In contrast to the tertiary amines, trialkylphosphines have strong donor properties and form exceedingly stable coordination complexes with a wide variety of metal salts such as those of univalent copper and gold, and bivalent platinum, palladium, and mercury.1 Like phosphine itself, many of these tertiary alkylphosphines are highly flammable, toxic, and extremely susceptible to air oxidation. Ease of oxidation first decreases and then increases as the alkyl group becomes larger.2 3,4 5 The n-butyl compound is thus a convenient member of this group for preparation. 

The bridged compound [Pt2Cl4(C2H4)2] (VI) has rather poor solubility in cold organic solvents, except in ethanol and acetone in which it is not very stable, and I attempted to obtain more soluble platinum(II)-ethylene complexes by introducing trialkylphosphines according to Eq. 

In 1949, Chatt (62) suggested that the trans influence of ligands like ethylene, carbon monoxide, and, to a lesser extent, trialkylphosphines in square-planar platinum (II) complexes was related to back donation of d-electron density from the transition metal to suitable empty orbitals of the ligands. It was proposed that such back bonding should be enhanced in PF3 complexes because of the presence of the highly electronegative fluorine atoms. 

Moreover, NMR studies have measured the coupling constant./,, of a number of trialkylphosphine platinum complexes. Trialkyl phosphines, as shown in Figures 7-la7 and b,s have a greater trans influence than Cl, and this is reflected in the higher coupling constant (/Pt P) and lower IR Pt-Cl stretching frequency... 

Since it is known that Pt—Cl bonds are also longer when trans to Me3P than trans to Cl (see 11), it is very probable that the high trans influence of trialkylphosphines also occurs through the ir-electrons. Thus, the ff-bonding of phosphines to platinum is stronger (more covalent) when tram to Cl than when tram to R3P, and it is to be expected that Pa-pt >- Pb-pt in [PtCl(Bu3P)3] . 

Chlorohydridobis(trialkylphosphine)pIatinum(II) complexes are useful as precursors to a variety of platinum hydrides " and platinum alkyls,as... 

The oxidative addition of disilanes occurs to palladium complexes of isonitrile ligands and platinum complexes of trialkylphosphine ligands as part of tiie catalytic silylation of alkynes and aryl halides. The addition of stannylboranes to Pd(0) complexes has also been reported,and the addition of diboron compounds to many metal systems, such as Pt(0) complexes (Equation 6.67), is now common. These reactions all occur with metal complexes that do not undergo intermolecular reactions with alkane C-H bonds, let alone C-C bonds. Thus, the Lewis acidic character of these reagents must accelerate the coordination of substrate and cleavage of the E-E bonds. 

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