Platinum Alkyl Research Articles

Kinetics and Mechanism of the Platinum(II)‐Catalyzed Hydroarylation of Vinyl Arenes with 1,2‐Dimethylindole

AbstractThe mechanism of the intermolecular hydroarylation of vinyl arenes (1) with 1,2‐dimethylindole (2) catalyzed by PtCl2 has been evaluated through a combination of kinetic analysis, deuterium labeling studies, and stereochemical analysis. The results of these and additional experiments are consistent with a mechanism for hydroarylation involving rapid and reversible complexation of vinyl arene to the catalytically inactive platinum mono(vinyl arene)complex trans‐PtCl2(H2C=CHAr)(solvent) to form the reactive platinum bis(vinyl arene) complex trans‐PtCl2(H2C=CHAr)2, which undergoes turnover‐limiting, outer‐sphere attack of indole. Rapid protodemetallation of the resulting platinum alkyl complex releases product and regenerates the equilibrating mixture of platinum π‐vinyl arene complexes.

Catalytic etherification of alcohols in Shilov system: C[sbnd]O versus C[sbnd]H bond activation

A novel catalytic reaction of alcohol etherification in the system ROH − PtCl42− ‐ PtCl62− was found. Methanol easily transforms into dimethyl ether in the presence of catalytic amounts of PtII chloro complexes at 70°C. Under the same conditions reaction of ethanol affords diethyl ether (catalytic) and π-ethylene PtII complex (stoichiometric). The reactions are accompanied by multiple H/D exchange, which is indicative of intermediacy of corresponding alkyl platinum derivatives. The plausible reaction mechanism involves oxidative addition of alcohol forming intermediate alkyl platinum(IV) derivative followed by decomposition of it via reductive elimination step under the action of alcohol giving the ether and regenerating catalyst. In the case of ethyl alcohol reaction, β-hydrogen abstraction from the intermediate Pt-ethyl species yields π-ethylene platinum(II) complex. Although it seems that the reaction does not involve the initial breaking of CH bonds of an alcohol, this system can be regarded as a model for studying of some peculiarities of Shilov chemistry, in particular, of isotope scrambling mechanisms in Shilov alkane activation.In contrast to reactions of dimethyl and diethyl ethers formation, tert-butyl ethers formation in CD3OH/t-BuOH medium is catalyzed by PtIV chloro complexes also and is not accompanied by isotope scrambling. These observations argue against intermediacy of alkyl platinum derivatives suggesting that acid-catalyzed mechanism operates in tert-butyl alcohol etherification.

Mechanism of Ethylene Migratory Insertion and Dimerization Catalyzed by δ -Alkyl Platinum Complexes-A DFT Study

The mechanism of ethylene insertion reactions catalyzed by cationic δ-alkyl platinum complexes has been studied at the B3LYP level of density functional theory. The initial steps of the reactions proceed via the coordination of ethylene to the reactants L2Pt(II)R+, where L2=none, (NH3)2, (CHNH)2; R=H, CH3, C2H5 in which ethylene coordinates strongly to the complexes PtCH+3 and PtC2H+5 (coordination energies (CE) are 296.52 and 229.28 kJ/mol, respectively), while nitrogen-containing ligands decrease the energies: Pt(NH3)2CH+3 (CE: 180.04 kJ/mol), Pt(NH3)2C2H+5 (CE: 97.86 kJ/mol), Pt(CHNH)2CH+3 (CE : 176.31 kJ/mol) and Pt(CHNH)2C2H+5 (CE: 91.00 kJ/mol). Moreover, ethylene insertion into the Pt-alkyl bond, which is the rate-determining step, is endothermic with barrier heights for L2PtCH3(C2H4)+ decreasing in the order: PtCH+3 (164.18 kJ/mol)>(NH3)2 PtCH+3 (129.95 kJ/mol)>(CHNH)2 PtCH+3 (115.27 kJ/mol), which has the same tendency for the ethyl case. The insertion product will continually undergo β-hydride elimination, which is exothermic. On the other hand, the effects of solvent (dichloromethane, THF and benzene) are investigated with PCM method, but the inclusion of the effects in the computations only slightly affects the results. Beside that, a complete catalytic cycle for ethylene dimerization is studied in detail and the calculations agree well with known energetic and recognized tendencies.

Platinum–alkyl–B(C 6F 5) 3 (or BF 3) ‘ in situ’ systems as tin(II) halide-free enantioselective hydroformylation catalysts

The dialkyl/diaryl-platinum complexes (Pt(CH 3) 2( bdpp); PtPh 2( bdpp) and Pt(2-Thioph) 2( bdpp), where bdpp stands for (2S,4S)-2,4-bis(diphenylphosphino)pentane) were reacted either with B(C 6F 5) 3, BPh 3 or BF 3. In the presence of PPh 3 or carbon monoxide cationic species with a general formulae [PtR(L)( bdpp)] + (L = PPh 3, CO) were formed exclusively. The ability of boron additives to provide vacant coordination site at the platinum made these systems suitable as hydroformylation catalysts. Enantioselective hydroformylation of styrene was carried out in the presence of in situ catalysts formed from Pt(alkyl/aryl) 2(bdpp) and B(C 6F 5) 3 or BF 3. Moderate e.e-s depending strongly on the structure of the catalytic precursor have been obtained. DFT/PCM calculations reveal an S N2-type reaction mechanism for the alkyl/aryl ligand abstraction with a notably lower activation barrier for BF 3.

Mechanisms of Reactions Related to Selective Alkane Oxidation by Pt Complexes

AbstractFor Abstract see ChemInform Abstract in Full Text.

Bis(phosphino)borates: a new family of monoanionic chelating phosphine ligands.

The reaction of dimethyldiaryltin reagents Me(2)SnR(2) (R = Ph (1), p-MePh (2), m,m-Me(2)Ph (3), p-(t)BuPh (4), p-MeOPh (5), p-CF(3)Ph (6)) with BCl(3) provided a high-yielding, simple preparative route to the corresponding diarylchloroboranes R(2)BCl (R = Ph (10), p-MePh (11), m,m-Me(2)Ph (12), p-(t)BuPh (13), p-MeOPh (14), p-CF(3)Ph (15)). In some cases, the desired diarylchloroborane was not formed from an appropriate tin reagent Me(2)SnR(2) (R = o-MeOPh (7), o,o-(MeO)(2)Ph (8), o-CF(3)Ph (9)). The reaction of lithiated methyldiaryl- or methyldialkylphosphines with diarylchloroboranes or dialkylchloroboranes is discussed. Specifically, several new monoanionic bis(phosphino)borates are detailed: [Ph(2)B(CH(2)PPh(2))(2)] (25); [(p-MePh)(2)B(CH(2)PPh(2))(2)] (26); [(p-(t)BuPh)(2)B(CH(2)PPh(2))(2)] (27); [(p-MeOPh)(2)B(CH(2)PPh(2))(2)] (28); [(p-CF(3)Ph)(2)B(CH(2)PPh(2))(2)] (29); [Cy(2)B(CH(2)PPh(2))(2)] (30); [Ph(2)B(CH(2)P[p-(t)BuPh](2))(2)] (31); [(p-MeOPh)(2)B(CH(2)P[p-(t)BuPh](2))(2)] (32); [Ph(2)B(CH(2)P[p-CF(3)Ph](2))(2)] (33); [Ph(2)B(CH(2)P(BH(3))(Me)(2))(2)] (34); [Ph(2)B(CH(2)P(S)(Me)(2))(2)] (35); [Ph(2)B(CH(2)P(i)Pr(2))(2)] (36); [Ph(2)B(CH(2)P(t)Bu(2))(2)] (37); [(m,m-Me(2)Ph)(2)B(CH(2)P(t)Bu(2))(2)] (38). The chelation of diarylphosphine derivatives 25-33 and 36 to platinum was examined by generation of a series of platinum dimethyl complexes. The electronic effects of substituted bis(phosphino)borates on the carbonyl stretching frequency of neutral platinum alkyl carbonyl complexes were studied by infrared spectroscopy. Substituents remote from the metal center (i.e. on boron) have minimal effect on the electronic nature of the metal center, whereas substitution close to the metal center (on phosphorus) has a greater effect on the electronic nature of the metal center.

Linear heterotrinuclear complexes derived from an alkyl platinum(II) twelve-membered macrocycle.

The P,N,P-tridentate ligand 2,6-bis(diphenylphosphino)pyridine, L, was employed to generate a twelve-membered metallomacrocyclic host species cis-Pt(2)Me(4)(mu-L)(2) that encapsulates Tl(I) and Cu(I) guest ions. The ligand was also used to synthesize another two linear heterotrinuclear complexes, [Me(2)Pt(mu-L)(2)Ag(2)(MeCN)(2)](BF(4))(2).MeCN and [(CO)(3)Fe(mu-L)(2)Ag(2)(Et(2)O)](ClO(4))(2), both containing a metal-metal dative bond (Pt-->Ag and Fe-->Ag, respectively) and stabilized by the d(10)-d(10) argentophilic interaction.

Insertion of Elemental Sulfur and SO2 into the Metal−Hydride and Metal−Carbon Bonds of Platinum Compounds

Elemental sulfur (S8) has been found to insert only one sulfur atom into the metal−hydride bonds of the platinum alkyl and aryl hydride complexes [(dcpe)PtRH] (dcpe = Cy2PC2H4PCy2). Unlike the parent compounds, the S-inserted complexes do not undergo reductive elimination to form the corresponding alkane- or arenethiols. Methane is lost from the methyl sulfhydryl complex. Sulfur dioxide was also found to insert into a platinum−methyl bond to form the corresponding S-bound sulfinate, which upon reacting with mineral acids generates methylsulfinic acid.

Cationic platinum(II) complexes: platinum–alkyl bond cleavage by a powerful Lewis acid

Treatment of [PtCl(Me)(dbbipy)] or [PtCl2(dbbipy)](dbbipy = 4,4′-di-tert-butyl-2,2′-bipyridine) with AgX (X = SO3CF3 or O2CCF3) gave the complexes [PtMe(SO3CF3)(dbbipy)]1, [Pt(SO3CF3)2(dbbipy)]2 and [Pt(O2CCF3)2(dbbipy)]5. The complexes [PtCl(SO3CF3)(dbbipy)]3 and [PtMe(O2CCF3)(dbbipy)]4 were prepared by the addition of HX to [PtCl2(dbbipy)] or [PtMe2(dbbipy)], respectively. Complex 1 reacted with CO to give the cationic carbonyl complex [PtMe(CO)(dbbipy)][SO3CF3]6a, which reacted with NEt2H to give an equilibrium with the corresponding carbamyl complex [Pt(CONEt2)Me(dbbipy)]7. In the first example of alkyl-ligand abstraction from a late-transition-metal complex by the powerful Lewis acid B(C6F5)3, the complexes [PtMeL(dbbipy)][BMe(C6F5)3](L = CO 6b or C2H48) were readily prepared from [PtMe2(dbbipy)] and B(C6F5)3 in the presence of L.

Unusually labile organoplatinum complexes: a mechanistic study of insertion–deinsertion into platinum–alkyl complexes of pyridine-2-carboxylic acid

Platinum–alkyl complexes of the general formula [PtR(pyca)L][R = Me, Hpyca = pyridine-2-carboxylic acid, L = PPh3, P(CH2Ph)3, P(C6H11)3, pyridine or 4-methylpyridine; R = Et, L = PPh3 or P(CH2Ph)3] and the complex [PtMe(hoqu)(PPh3)](Hhoqu = 8-hydroxyquinoline) have been prepared and their carbonylation activity studied. The complexes show a large variation in carbonylation behaviour, which is markedly dependent on the ligands attached to the platinum centre. The donor capacity of L and the rigidity of the chelating ligand are major factors. For complexes containing pyca as the chelating ligand; where R = Me or Et and L = PPh3, acyl complexes are readily prepared; where R = Et and L = P(CH2Ph)3, a mixture of two products is formed, the expected acyl complex [Pt(COEt)(pyca){P(CH2Ph)2}] and a compound with a terminal CO ligand in which the pyca ligand is monodentate [Pt(CO)(COEt)(pyca){P(CH2Ph)3}]; where L = P(C6H11), pyridine or 4-methylpyridine, no carbonylation occurs. With the complex containing the rigid hoqu ligand no carbonylation occurs. The complexes [Pt(COMe)(pyca)-(PPh3)] and [PtEt(pyca)(PPh3)] are unusually labile, eliminating CO or ethylene when warmed, giving [PtMe(pyca)(PPh3)] or platinum–hydride complexes respectively. The behaviour of these complexes and the carbonylation behaviour of the platinum–alkyl complexes has been studied in detail and a mechanism for the insertion–deinsertion reactions is proposed.

Hydrocarbon oxidation in solutions containing platinum complexes

1. Oxidation of saturated hydrocarbons in solutions containing chloride platinum complexes leads to the formation of unstable alkyl platinum compounds and chloro derivatives as primary reaction products, these being subsequently converted to alcohols, esters, ketones, and aromatic compounds as the result of oxidational chlorination, dehydrochlorination, and solvolysis. 2. In the case of acetic acid, it was shown that platinum salts can be used to catalyze the oxidation of alkanes by oxygen, copper salts, and quinones.

ChemInform Abstract: A MASS SPECTROSCOPIC STUDY OF PLATINUM ALKYL AND ARYL COMPLEXES

Chemischer InformationsdienstVolume 5, Issue 31 Organoelement Compounds ChemInform Abstract: A MASS SPECTROSCOPIC STUDY OF PLATINUM ALKYL AND ARYL COMPLEXES F. GLOCKLING, F. GLOCKLINGSearch for more papers by this authorT. MCBRIDE, T. MCBRIDESearch for more papers by this authorR. J. I. POLLOCK, R. J. I. POLLOCKSearch for more papers by this author F. GLOCKLING, F. GLOCKLINGSearch for more papers by this authorT. MCBRIDE, T. MCBRIDESearch for more papers by this authorR. J. I. POLLOCK, R. J. I. POLLOCKSearch for more papers by this author First published: August 6, 1974 https://doi.org/10.1002/chin.197431432AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume5, Issue31August 6, 1974 RelatedInformation

The crystal and molecular structure of trans-PtI(CMeNC 6H 4Cl)-(PEt 3) 2: A compound derived from the insertion of an isocyanide into a metalcarbon bond

The title compound, obtained from the reaction of the platinum alkyl compound, PtI(Me)(PEt 3) 2, and p-chlorophenyl isocyanide, crystallizes in the monoclinic space group P2 1 / c with four molecules per unit cell with dimensions a 20.903(3), b 8.531(1), c 15.176(2)Å and β = 107.76(1)°. Its crystal and molecular structure was determined, and refined by full-matrix isotropic-anisotropic least squares on 1791 independent counter data, to a final unweighted R factor of 3.8%. The structure of this species consists of discrete molecular units, in which the platinum atom assumes its expected four-coordinate square planar geometry with PtP distances of 2.314(3) and 2.321(3)Å, a PtI distance of 2.712(1)Å, and a PtC distance of 2.027(11)Å. The intramolecular PtN distance, the distance between the nitrogen of the acylimino-group and the metal atom, is found to be 3.042(10)Å. This is clearly a non-bonding distance, refuting an earlier suggestion based on PMR data that the metal atom achieves pseudo five-coordination in these species through coordination to this atom. No unusual intermolecular distances are observed in this structure, with the closest PtPt distance being 8.531 Å.

A mass spectroscopic study of platinum alkyl and aryl complexes

A mass spectroscopic study is reported on compounds of the type PtR 2L 2 where L = PR 3 or L 2 = a chelating diphosphine and R = alkyl or aryl. Various factors affecting fragmentation paths and ion abundances have been identified. Rearrangement processes occur in which organic groups are transferred to and from P and Pt, and a mechanism is proposed whereby polyphenyl ions are formed. The thermal decomposition of PtAr 2(PPh 3) 2 (Ar = Ph, m- and p-FC 6H 4) produces at 110–150°C yellow or red platinum cluster compounds.

Infrared Spectra of Some Alkyl Platinum Compounds. Part II. Assignment of the CH Stretching Modes of a Methyl Group

Several isotopically substituted triphenylphosphine stabilized dimethyl platinum compounds of the type (Ph3P)2PtMe2 where Me = CH3, CH2D, CD2H, and CD3 have been prepared and their infrared spectra in the CH and CD Stretching regions have been examined. The assignments of the stretching vibrations of the methyl group have been confirmed by means of an application of the Average Rule for isotopically substituted species. The possible application of the Average Rule as a general method for assigning CH stretching modes is discussed and it is suggested that the method could be used to confirm some recently proposed reassignments of the traditional Fox and Martin assignments. The method may also be used by surface chemists as a means of determining the number of hydrogen atoms in an adsorbed XHn species.

Infrared spectra of some alkyl platinum compounds. Part I. Comparison with the spectra of chemisorbed hydrocarbons

A series of triphenylphosphine stabilized platinum dialkyl compounds of the type (Ph2P)3PtR2 where R = methyl, ethyl, ethyl-d3, n-propyl, n-butyl, and n-hexyl have been synthesized and their infrared spectra in the CH stretching region have been obtained. These spectra are discussed in terms of the infrared spectra of hydrocarbons which are chemisorbed on transition metal catalysts.

Insertion reactions involving isocyanide ligands in platinum alkyl and aryl complexes

Insertion reactions involving isocyanide ligands in platinum alkyl and aryl complexes

The formation of alkylplatinum carbonyl chlorides by treatment of a tetrachloroplatinate with olefins and formic acid

Several members of a new class of organometallic compound having stoicheiometry CnH2n+ 1PtCOCl were prepared by the reaction of lithium tetrachloroplatinate(II) with a terminal olefin and formic acid in dimethylformamide solution. There was little difference in the thermal stabilities of the higher and lower members of the series. These compounds, which probably have a dimeric structure, gave monomeric derivatives with acetylacetone and aniline in which the alkyl–platinum and carbon monoxide–platinum groups are retained, but with phosphines displacement of carbon monoxide occurs together with the formation of acyl–platinum derivatives.Butadiene reacted with the above reaction mixture to give crystals of composition Li2[PtCl3·C4H6PtCl3], 6HCONMe2.

Metal-Olefin Compounds. IV. The Preparation and Properties of Some Aryl and Alkyl Platinum(II)-Olefin Compounds

Metal-Olefin Compounds. IV. The Preparation and Properties of Some Aryl and Alkyl Platinum(II)-Olefin Compounds