Triethylphosphine complexes

Figure 2.57 Interconversion between rhodium triethylphosphine complexes.

Figure 2.59 Interconversion between dimeric triethylphosphine complexes.

Coates, G.E., Kowala, C. and Swan, J.M. (1966) Coordination compounds of Group IB metals. I. Triethylphosphine complexes of Au(I) mercaptides. Australian Journal of Chemistry, 19, 539-545. 

Hydrogen does not add to Pt(PPh3)3> but the triethylphosphine complex Pt(PEt3)3 does to give PtH2(PEt3)3.65... 

Since a trigonal-prismatic transition state with greater steric hindrance must be traversed, it thus becomes understandable why the compound with the very bulky tricyclohexylphosphine ligand isomerizes more slowly than does the corresponding triethylphosphine complex. 

Although the triethylphosphine complexes of nickel(H) may not necessarily represent optimum examples of catalysts,(12)(13) they allowed us access to the key intermediate, viz., tHe siryl-methyl-nickel complexes such as la and b. Any catalytic cycle... 

In this group, too, the first observations were made by Thiele 192), who found that cuprous and silver ions are precipitated from aqueous ammoniacal solution by cyclopentadiene, but gave no analytical data. Thallium was later found to be precipitated similarly. Copper (I), however, also yields a white crystalline cyclopentadienyl-triethylphosphine complex, C5H5CuP(C2H5)3, which is stable to water 215) this was, in fact, analogous to an earlier method described by van Peski and Melsen. Attempts to make a complex by the Grignard reagent method or by the action of cyclopentadienyl sodium on cuprous halides were unsuccessful. 

Operation of reverse solvento steps have been detected also in reactions of a number of triethylphosphine complexes of platinum. Under pseudo-first-order conditions, the rate of replacement of CU from trans-[PtCl2(PEt3)2] by N02 in MeOH deviates markedly from linearity due to the operation of reaction (12) 34). 

In Table A.2 the entry under Bond specifies the atom pair to which the lines refer and follows the ligand sequence given in Table A.3. In the case of triethylphosphine complexes (Section 8.5.2), for example, there are 11 blocks, in which the bond column contains P-C as the first entry, followed by 10 entries for Cr-P through to Pt-P the section thus gives statistics for both intra-ligand and metal-ligand atom pairs. 

In triethylphosphine complexes of the type cis- and trans-[PtCl2(Et3P)2], heteronuclear double-resonance experiments have shown that the signs of the Jpcn - pcch coupling constants are negative and positive, respectively. ... 

No sandwich or 7r-complex seems to be involved. One might observe in general that the isolation of organometallic compounds of low stability may often succeed if complex formation with solvent, metallic salt, or an RM type is provided for (See Section IV.A.3). For example, disubstituted platinum (II) and palladium (II) derivatives have been prepared successfully as the bis(triethylphosphine) complexes in the following reaction (19, 20) ... 

The formation of such Lewis complexes may find increasing application in stereochemical studies. Two cases in point might be cited. First, etherate formation allows the isolation of the optically active tri-2-methylbutyl-aluminum etherate (97). This compound is stable to racemization up to 100°. Second, diphenylpalladium (II) has recently been prepared as its bis-triethylphosphine complex in both a cis- and a irans-planar complex form (20). The latter seems to represent the first example of geometrical isomerism among organometallic compounds (Section II.D). 

The air-stabilities of the complexes in Table I vary widely. Isocyanide complexes and complexes of the alkyl phosphines are very air sensitive or pyrophoric. The aryl phosphine complexes are moderately air sensitive the phosphite complexes can be handled in air but should be stored in an inert atmosphere. The phosphite complexes are insoluble in polar solvents such as alcohols and water, and soluble in hydrocarbons. Aryl phosphine complexes are soluble in aromatic solvents or tetrahydrofuran and insoluble in alkanes and alcohols. The alkyl phosphine complexes are soluble in ethers and hydrocarbons the triethylphosphine complex dissociates to the deep-purple tris complex, and is protonated by alcohols. 

Some chemistry of platinum triethylphosphine complexes is shown below ... 

Since the rate law for the triethylphosphine complexes reduces to that of the bipy and AsEtg compounds when ksjk (k) is small it can be inferred that CI is much more reactive towards triethylphosphine solvent-complex intermediates than those formed by the bipy and AsEts complexes. Values of lie in the range 7.8— 9.7 kcal mol while AS" " = — 30 to —33 cal mol, which is taken as evidence for an intermediate activated complex with Cl bridging the Pt and Au species. Since at least three mechanisms involving such an intermediate can account for the kinetic data the actual redox pathway cannot be assigned unambiguously. 

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