Neutral organocopper(III) complexes

Neutral organocopper(III) complexes have been prepared from organocuprate(I) reagents and alkyl halides in the presence of certain strongly electron donating ligands.     

Theoretical study of the reactivity of Rh(I) and Rh(III) Bis(isonitrile) complexes in cycloaddition reactions with nitrones

The mechanism of 1,3-dipolar cycloaddition of nitrone (CH₂=N(Me)O) to methylisonitrile coordinated to Rh(I) and Rh(III) in the [RhCl(PH₃)(CNMe)₂] and [RhCl₃(PH₃)(CNMe)₂] complexes has been studied by quantum-chemical methods. The molecular and electronic structures of the cycloaddition products, the nature of transition states, the mechanism of reactions, their kinetic and thermodynamic parameters, and the solvent effect have been described. The reactions occur via the concerted strongly asynchronous mechanism involving the formation of a five-membered cyclic transition state. The use of rhodium complexes as reagents leads to a noticeable decrease in the activation barriers of the processes under consideration and an increase in the magnitudes of energy effects of the reactions. It has been demonstrated that the Rh(III) complexes are better activators of the cycloaddition of nitrone to isonitrile than the Rh(I) complex. The calculations predict that in the case of the Rh(I) complexes, only one isonitrile ligand can be involved in cycloaddition of nitrone, whereas the use of the Rh(III) complexes enables the participation of both ligands. The solvation effects inhibit the reactions.     

Anomalous structure-luminescence relationship in phosphorescent gold(I) isonitrile neutral complexes

A new compound that exhibits the shortest intermolecular Au...Au distance ever reported for neutral RNCAuX complexes is found to exhibit a counterintuitive higher-energy Au-centered phosphorescence than that in an analogous compound with a much longer Au...Au distance, presumably due to a different extent of excited-state distortion in dimers vs. extended chains.     

Photogeneration and reactions of cobalt(I) complexes

Cobalt(I) polypyridine complexes (which are capable of reducing H⁺ to H₂ and CO₂ to CO) may be generated from polypyridineruthenium(II) excited-state reactions by a variety of routes. The relation between the energetics and the rate constants for these routes are considered. In addition, factors leading to loss of cobalt(I) and the mechanisms of substrate reduction are discussed.     

The preparation and catalytic hydroformylation activity of some halocarbonylrhodium(I) complexes containing phosphinoalkylorganosilicon ligands

The synthesis and properties of a series of trans-halocarbonylrhodium(I) complexes containing the phosphinoalkylorganosilicon ligands Me₃SiCH₂PPh₂, Me₃Si(CH₂)₃PPh₂, and PPh₂CH₂(Me)$\text{Si(OSiMe}{}_2\text{)}{}_3\text{O}$ have been investigated. The complexes could be prepared by an exchange reaction involving RhCl(CO)(PPh₃)₂ and the organosilicon ligands or in better yields by the reaction of Rh₂Cl₂(CO)₄ with the ligands. Iodorhodium derivatives were obtained as the exclusive products in the latter reaction if a small amount of LiI was present. The catalytic activity of RhCl(CO)(PPh₂CH₂SiMe₃)₂ was similar to that of RhCl(CO)(PPh₃)₂ in the hydroformylation of hex-1-ene at 100°C and 1000 psi pressure of H₂/CO. The catalytic properties of the iodo derivatives RhI(CO)L₂ [L = Me₃SiCH₂PPh₂, Me₃Si(CH₂)₃PPh₂, and PPh₂CH₂(Me)$\text{Si(OSiMe}{}_2\text{)}{}_3\text{O}$] varied considerably, with RhI(CO)(PPh₂CH₂SiMe₃)₂ producing an unexpectedly low linear/branched aldehyde product ratio.     

Oxidative addition reactions of carbon diselenide and areneselenols to some iridium(I) and platinum(0) complexes

Reaction of carbon diselenide in 3 to 1 molar ratio, and areneselenols in equimolar ratio, with trans-IrCl(CO)(PPPh₃)₂ and PtL₄, gives oxidative addition products, IrCl(CO)CSe₂)(PPh₃)₂, Pt(CSe₂)L₂, IrHCl(CO)(SeC₆H₄Me-p)(PPh₃)₂, and PtH(SeR)L₂, respectively (R = Ph and p-MeC₆H₄; L = PPh₃ and PPh₂Me). However, reactions of PtL₄ with an excess of areneselenols afford bis(arylselenide) complexes Pt(SeR)₂L₂. The configurations of these complexes are discussed on the basis of their IR and PMR spectra. The carbon diselenide adducts are suggested to have configurations similar to the corresponding carbon disulfide adducts. The platinum hydrides are found to exist as a mixture of cis and trans isomers in solution, both the isomers being labile with regard to dissociative exchange of the tertiary phosphine ligands. The trans configurations of Pt(SeR)₂(PPh₂Me)₂ are unambiguously shown by the virtually coupled triplet pattern of the PPh₂Me signals.     

Synthesis,reactions and catalytic activity of some mixed trifluorophosphine(triphenylphosphine)hydrido complexes of cobalt(I)

The complexes CoH(PF₃)_4?n (PPh₃)_n (n = 1–3) have been prepared by low from the reaction between CoH(PF₃)(PPh₃)₃ and butadiene. The hydrido complexes are active catalysts for the isomerisation of 1-octene to 2-octene under hydrogen or nitrogen.     

Further reactions of some bis(vinylidene)diruthenium complexes

Whereas {Ru(dppm)Cp*}₂(μ-CCCC) (2) is the only product formed by deprotonation of [{Ru(dppm)Cp*}₂{μ(CCHCHC)}]⁺ with dbu, a mixture of 2 with Ru{CCCHCH(PPh₂)₂[RuCp*]}(dppm)Cp* (3) and {Cp*Ru(PPh₂CHCCH-)}₂ (4) is obtained with KOBu^t. A similar reaction with [{Ru(dppm)Cp*}₂{μ(CCMeCMeC)}]⁺ (5) gave Ru{CCCMeCH(PPh₂)₂[RuCp*]}(dppm)Cp* (6). X-ray structures of 4, 5 and 6 confirm the presence of the 1-ruthena-2,4-diphosphabicyclo[1.1.1]pentane moiety, which is likely formed by an intramolecular attack of the deprotonated dppm ligand on C(1) of the vinylidene ligand. Protonation of {Ru(dppe)Cp*}₂(μ-CCCC) (8-Ru) regenerates its precursor [{Ru(dppe)Cp*}₂{μ(CCHCHC)}]²⁺ (7-Ru). Ready oxidation of the bis(vinylidene) complex affords the cationic carbonyl [Ru(CO)(dppe)Cp*]PF₆ (9) (X-ray structure).     

The behaviour of some functionally substituted α-allenic alcohol derivatives toward organocopper(I) species

Trimethylsilyl ethers of 2,3-hexadien-5-yn-1-ols (1) undergo carbocupration at the terminal triple bond, and this reaction has been used to prepare, among other species, the trimethylsilyl ethers of 8-trimethylsilyl-2,3,5-octatrien-7-yn-1-ols(6a and 7a). When the terminal triple bond of 1 is protected with a trimethylsilyl group S_N2′-like displacements take place upon addition of RCu, with predominant formation of E-dienynes in which H is present instead of R, especially when s-BuCu is used. Only when R is methyl is the R group transferred. On the other hand, smooth formation of dienynes bearing the R group are observed upon reaction of methanesulfinates with RCu; in this case, however, the configuration of the dienynes is mainly Z. A mechanistic rationalization of the results is proposed.     

Cross-coupling reactions of gold(I) alkynyl and polyyndiyl complexes

Gold(I) alkynyl complexes are shown to efficiently couple with aryl iodides under mild conditions in the presence of both Pd(II) and Cu(I) co-catalysts. The reaction is not gold catalysed, but rather the Au(I) centre serves to transfer the alkynyl moiety to Cu(I), which then enters the conventional Sonogashira cycles. Using this method, a small range of 1,4-disubstituted diynes, including examples of differentially substituted compounds ArCCCCAr′, have been prepared directly from [(Ph₃P)AuCCCCAu(PPh₃)] and aryl iodides ArI.     

Synthesis and reactions of beta-diketiminato divanadium(I) inverted-sandwich complexes

Reduction of VCl(2)(Nacnac) (Nacnac = HC(C(Me)NC(6)H(3)-iPr(2))(2)) with KC(8) in toluene leads to the formation of a toluene-bridged inverted-sandwich divanadium(I) complex, (mu-eta(6):eta(6)-C(7)H(8))[V(Nacnac)](2), which behaves as a source of V(Nacnac) and a multi-electron reductant in the two reactions studied in this report.     

Protonation reactions of dinuclear pyrazolato iridium(I) complexes

The complex [[Ir(mu-Pz)(CNBu(t))(2)](2)] (1) undergoes double protonation reactions with HCl and with HO(2)CCF(3) to give the neutral dihydride complexes [[Ir(mu-Pz)(H)(X)(CNBu(t))(2)](2)] (X = Cl, eta(1)-O(2)CCF(3)), in which the hydride ligands were located trans to the X groups and in the boat of the complexes, both in the solid state and in solution. The complex [[Ir(mu-Pz)(H)(Cl)(CNBu(t))(2)](2)] evolves in solution to the cationic complex [[Ir(mu-Pz)(H)(CNBu(t))(2)](2)(mu-Cl)]Cl. Removal of the anionic chloride by reaction with methyltriflate allows the isolation of the triflate salt [[Ir(mu-Pz)(H)(CNBu(t))(2)](2)(mu-Cl)]OTf. This complex undergoes a metathesis reaction of hydride by chloride in CDCl(3) under exposure to the direct sunlight to give the complex [[Ir(mu-Pz)(Cl)(CNBu(t))(2)](2)(mu-Cl)]OTf. Protonation of both metal centers in [[Ir(mu-Pz)(CO)(2)](2)] with HCl occurs at low temperature, but eventually the mononuclear compound [IrCl(HPz)(CO)(2)] is isolated. The related complex [[Ir(mu-Pz)(CO)(P[OPh](3))](2)] reacts with HCl and with HO(2)CCF(3) to give the neutral Ir(III)/Ir(III) complexes [[Ir(mu-Pz)(H)(X)(CO)(P[OPh](3))](2)], respectively. Both reactions were found to take place stepwise, allowing the isolation of the intermediate monohydrides. They are of different natures, i.e., the metal-metal-bonded Ir(II)/Ir(II) compound [(P[OPh](3))(CO)(Cl)Ir(mu-Pz)(2)Ir(H)(CO)(P[OPh](3))] and the mixed-valence Ir(I)/Ir(III) complex [(P[OPh](3))(CO)Ir(mu-Pz)(2)Ir(H)(eta(1)-O(2)CCF(3))(CO)(P[OPh](3))].     

Synthesis, spectroscopic characterization and electronic structure of some new Cu(I) carbene complexes

Reaction of oligomeric Cu(I) complexes [Cu(Μ-S-C(=NR)(O-Ar-CH₃)]_n with Lewis acids gave Cu(I) carbene complexes, which were characterized by¹H and¹³C NMR spectroscopy. Cu(I) carbene complexes could be directly generated from RNCS, Cu(I)-OAr and Lewis acids; this method can be used to prepare Cu(I) carbene complexes with different substitutents on the carbene carbon. The complexes were unreactive towards olefins and do not undergo cyclopropanation. Electronic structure calculations (DFT) show that the charge on the carbene carbon plays an important role in controlling the reactivity of the carbene complex.     

8-Oxyquinolate iridium(I) complexes and their oxidative-addition reactions

The novel sixteen-electron complex [Ir(Oq)(COD)] (Oq = 8-oxyquinolate; COD = 1,5-cyclooctadiene) adds monodentate phosphines, phosphites or activated olefins irreversibly to give pentacoordinate iridium(I) complexes of the type [Ir(Oq)(COD)L] (L = PPh₃, P(OPh)₃, maleic anhydride or tetracyano-ethylene). Reaction of [Ir(Oq)(COD)] with some diphosphines leads to substitution products of the general formula [Ir(Oq)(diphos)] (diphos = 1,2-bis(diphenylphosphino)ethane or cis-1,2-bis(diphenylphosphino)ethylene). Carbon monoxide displaces the COD group from the complexes giving either [Ir(Oq)(CO)₂] or [Ir(Oq)(CO)L], and the latter undergo oxidative addition reactions with SnCl₄, Me₃SiCl, Me₃SnCl, MeI, allylbromide, PhCOCl, MeCOCl, Cl₂, Br₂, TlCl₃ and HCl leading to novel iridium(III) complexes.     

Well-defined (N-heterocyclic carbene)-Ag(I) complexes as catalysts for A3 reactions

The use of well-defined (N-heterocyclic carbene)-Ag(I) complexes for the A(3) reaction allows for the coupling of unactivated aldehydes at room temperature and very short reaction times.     

Photochemistry of neutral isonitrile gold(I) complexes: modulation of photoreactivity by aurophilicity and pi-acceptance ability

This work demonstrates for the first time that aurophilicity and ligand pi-acceptance ability sensitize the photoreactivity of Au(I) complexes. Photolysis of LAu(I)Cl (L = RNC or CO) complexes leads to free L, Au(III), and Au(0) photoproducts. Solutions of (p-tosyl)CH(2)NCAuCl in dichloromethane undergo significant oligomerization leading to dimers and trimers with formation constants of 1.61 x 10(3) and 6.61 x 10(3) M(-1), respectively, representing the highest values reported to date for complexes that exhibit aurophilic association in solution. The photoproduct quantum yield (Phi) varies with the LAu(I)Cl concentration in solution. For (p-tosyl)CH(2)NCAuCl, metallic gold forms with Phi = 0.0065 and 0.032 in 4.0 x 10(-5) and 4.0 x 10(-3) M dichloromethane solutions, respectively. Meanwhile, irradiation of t-BuNCAuCl primarily produces t-BuNCAuCl(3) with Phi = 0.0045 and 0.013 for 5.0 x 10(-5) and 5.0 x 10(-3) M dichloromethane solutions, respectively. For Au(CO)Cl, metallic gold forms with Phi = 0.013 and 0.065 upon irradiation of 8.0 x 10(-5) and 8.0 x 10(-3) M dichloromethane solutions, respectively. Hence, *[LAuX](n) oligomeric species are more photoreactive than monomeric species. The results also demonstrate intuitive control of Phi via modulation of the pi-acceptance ability of L, as both follow CO > (p-tosyl)CH(2)NC > (alkyl)NC in LAuCl, a trend that is also commensurate with the relative long-term photosensitivity of the corresponding solids and solutions. A new method for preparing stable small gold nanoparticles is described based on the fundamental findings above. Thus, photolysis of different concentrations of LAuX in solutions containing a primary amine-terminated dendrimer leads to clear solutions exhibiting tunable visible plasmon absorptions of gold nanoparticles; these solutions maintain their colors and stability indefinitely. TEM measurements for representative samples prepared by photolysis of (p-tosyl)CH(2)NCAuCl solutions give rise to spherical nanoparticles as small as 5 nm.     

Synthesis and structure of neutral and cationic pentahaloarylpalladium(II) isonitrile complexes

Complexes of the types (a) trans- and cis-[Pd(C₆X₅)₂ (CNR)₂], (b) trans- [Pd(C₆X₅)Cl(CNR)₂] and (c) [Pd(C₆X₅)(CNR)₃]ClO₄ (X = F or Cl;R = Bu^t cyclohexyl or p-tolyl) have been made by replacement of the tetrahydrothiophen or Cl groups of appropriate precursors by isonitrile. Their structures have been assigned on the basis of their IR and ¹H NMR spectra.