Phosphite complexes of platinum

Phosphite complexes of platinum(0) have received substantially less attention than have phosphine complexes.44 [Pt P(OC6H4OMe-2)3 3] can be prepared by reduction of the [PtCl2 P-(OC6H4OMe-2)3 2] complex in the presence of the phosphite or by the reaction of the phosphite with Lris(//2-norbornene)platinum(II) 44 Alkene complexes of bis(phosphite)platinum(II) can be prepared in a similar manner to the analogous phosphine complexes. 

Tertiary phosphite complexes of platinum(O) can be prepared by the hydrazine reduction of PtCl2 P(OR)3 2 (equation 384), or by replacement of triphenylphosphine in Pt(PPh3)3 (equation 385).1233 Alternatively the complexes can be prepared from Pt(j73-C3H5)(r/5-Cp) and the phosphite.1268 Heteronuclear INDOR measurements show that 2/(PP) has a value of +81 Hz in Pt P(OMe)3 4. A detailed synthesis of Pt P(OEt)3 4 has been published from K2PtCl4 and triethyl phosphite with KOH (equation 386).1267 The product is obtained as colorless crystals which can be handled in air. 

For platinum(II) complexes with alkylphosphine ligands there is a small but marked dependence of the values (PC) on the nature of the group tram to phosphine.1353 By analogy with the earlier method using 3H NMR, 13C 1H NMR techniques using virtual coupling have been used for phosphite complexes of platinum(II), but it does not appear that the method can be generally used to determine stereochemistry.1354... 

Tri-ra-butylphosphite, tri-ra-butylarsine, and tri-ra-butylstibine complexes of platinum(O) have been prepared by the reaction of the ligand with pt(COD)2] or, in the case of the phosphite, by reaction with [Pt(PPh3)4].38 All form four-coordinate complexes when 4 mole-equivalents of ligand are used, but when 2 or 3 mole-equivalents of the phosphite ligand are used, mixtures of three- and four-coordinate complexes are observed.38... 

A study of sequential Arbuzov-type demethylation reactions of the platinum(II)-phosphite complex [Pt P(OMe)3 4]2+, in which the phosphite ligands are converted to phosphonates, has been described.285 Many of the products of the reaction were characterized by NMR spectroscopy and X-ray crystallography.286 The X-ray structures are the first reported for trialkylphosphite complexes of platinum(II). 

TRIARYL PHOSPHITE COMPLEXES OF COBALT, NICKEL, PLATINUM, AND RHODIUM... 

The phosphine and phosphite complexes of rhodium, cobalt, and platinum are commonly used as catalysts for hydroformylation of olefins (Eq. 7). Other... 

To prepare complexes with different phosphites it may be important to use either THF as reaction solvent, or if an alcohol solvent is desired, the alcohol having the same alkyl substituents as the phosphite must be used in order to avoid problems with transesterification of the phosphite ligand. The equilibrium between tetra- and penta-coordination (equation 410) is controlled by steric effects. Using similar synthetic procedures the alkyl diphenylphosphinite complexes of platinum [Pt PPh2(OR) 4](BPh4)2 (R = Me, Et) can also be prepared. Unexpectedly the reaction between Pt(l-a,4,5- j-CiHi3)(cod) and P(OR)3 (R = Me, Et, Ph) gives the hydride complex [PtH P(OR)3 4] . ... 

The d phosphine and phosphite complexes of zerovalent nickel, palladium and platinum possess long-lived emissive excited states in both fluid solution and in the solid state.The lifetimes of the Ni and Pd complexes are in the 1.39-5.38 ps range, with the platinum complex Pt(PPh3)4 having the shorter excited state lifetime of 0.07 //s because of spin-orbit coupling. These long lifetimes allow for bimolecular reactions to occur, and under photochemical conditions chlorobenzene will add to the complex Pd(PPh3)3 (Ref. 75) ... 

Phosphorus-31 2D-EXSY NMR spectra have afforded evidence of sym-cis/sym-trans interconversions in a series of cyclopalladated tertiary phosphite complexes of type [Pd(/i-Cl)(P(OR )2(OC6H3R ))]2. The platinum analog behaved in a similar manner/ P NMR 2D-EXSY spectroscopy was also employed to probe the dynamics of interconversion between covalent and dative metal-bonded isomers of the mixed metal dinuclear complex [NiPd(CNMe)3(dppm)2](PF6)2. Isomer populations were strongly solvent-dependent with free energies of activation for interconversion of ca 67 kJ mol at 298 Dinuclear complexes of trimethylplatinum(IV) halides have been synthesized (26). The dominant solution structures were... 

Other notable examples are the orthometallation (orthophenylatioti) reactions of many complexes of aryl phosphines (PAr3) and aryl phosphites P(OAr)3 with platinum metals in pailiculai, e,g, ... 

The first examples of five-coordinate platinum(II) complexes of the type [Pt(PR3)L]2+ (L = tris(2-(diphenylphosphino)ethyl)phosphine R = Et, OMe, OEt) (104) containing only P-donor atoms have been prepared by the reaction of [PtClL]+ with an appropriate monodentate tertiary phosphine or phosphite ligand.284 Triaryl phosphines and phosphites do not react with the precursor complex, even at elevated temperatures, most probably due to the considerable steric interactions that would occur upon the approach of the P-donor ligand to the platinum(II) center. 

Tris- and tetrakis(triaryl phosphite)platinum(O) complexes have been prepared by reduction of platinum(II) phosphite derivatives with hydrazine.5 The tetrakis complexes have also been prepared by ligand exchange processes, and the synthesis described here is based on this latter procedure. The chemistry of platinum phosphite complexes has not been extensively studied. 

Note. The triaryl phosphite complexes, with the possible exception of the platinum derivative, appear to interact with oxygen when prepared or manipulated in the presence of air. This interaction, which leads to large fluctuations in melting behavior, does not cause any other apparent changes. However, in view of these observations, it is recommended that all preparations and subsequent manipulations of the complexes be performed in a nitrogen-filled dry-box. 

The platinum(II) phosphite complex [Pt2(P205H2)4]4 has a tetrabridged structure. It is readily oxidized to Ptm dimers [PL OsH LJ2. On photolysis they oxidize organic substrates and are capable of cleaving DNA.16... 

Platinum(II)-phosphorus distances in phosphine and phosphite complexes are usually between 2.2 and 2.4 A. The distances are affected by the ligand trans to phosphorus in the square plane. For a complete listing of platinum-phosphorus distances in such structures the reader is directed to Molecular Structures and Dimensions for structures from 1935-1976, and to the BIDICS series for structures published up through 1981. A list of representative structures and Pt—P bond distances is shown in Table 7. The Pt—Cl distance of 2.344(2) A in cis-PtCl2(PEt3) P(OPh)3 for the chloride trans to P(OPh)3 is shorter than that (2.355(2) A) for the chloride trans to PEts, implying a weaker trans influence of P(OPh)3 than of PEt3. ... 

Tetrachloropalladate(II) ion catalyzes the interconversion of 1- and 2-butenes in aqueous solutions containing chloride and hydronium ions. Sodium tetrachloropalladate(II) catalyzes the conversion of allylbenzene to propenyl-benzene in acetic acid solutions. Tetrakis(ethylene))Lt,/x -dichlororhodium(l) catalyzes butene isomerization in methanolic hydrogen chloride solutions . Cyclooctadienes isomerize in benzene-methanol solutions of dichlorobis-(triphenylphosphine)platinum(11) and stannous chloride. Chloroplatinic acid-stannous chloride catalyzes the isomerization of pentenes. Coordination complexes of zero-valent nickel with tris(2-biphenylyl)phosphite or triphenyl-phosphine catalyze the isomerization of cis-1,2-divinylcyclobutane to a mixture of c/5,m-l, 5-cyclooctadiene and 4-vinylcyclohexene . Detailed discussions of reaction kinetics and mechanisms appear in the papers cited. 

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