There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Pick your Pd partners: A number of catalytic systems have been developed for palladium-catalyzed CH activation/CC bond formation. Recent studies concerning the palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle are discussed (see scheme), and the versatility and practicality of this new mode of catalysis are presented. Unaddressed questions and the potential for development in the field are also addressed.

In the past decade, palladium-catalyzed CH activation/CC bond-forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming CC bonds from CH bonds: PdII/Pd0, PdII/PdIV, Pd0/PdII/PdIV, and Pd0/PdII catalysis. A more detailed discussion is then directed towards the recent development of palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle. Despite the progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge.

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Palladium(II)-catalyzed C-H activation/C-C cross-coupling reactions: versatility and practicality.

1. Advantages of Chemical Redox Agents 878 2. Disadvantages of Chemical Redox Agents 879 C. Potentials in Nonaqueous Solvents 879 D. Reversible vs Irreversible ET Reagents 879 E. Categorization of Reagent Strength 881 II. Oxidants 881 A. Inorganic 881 1. Metal and Metal Complex Oxidants 881 2. Main Group Oxidants 887 B. Organic 891 1. Radical Cations 891 2. Carbocations 893 3. Cyanocarbons and Related Electron-Rich Compounds 894

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Chemical Redox Agents for Organometallic Chemistry

Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

The new ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) approach has been proposed and shown to be successful in reproducing benchmark calculations and experimental results. ONIOM3, a three-layered version, divides a system into an active part treated at a very high level of ab initio molecular orbital theory like CCSD(T), a semiactive part that includes important electronic contributions and is treated at the HF or MP2 level, and a nonactive part that is handled using force field approaches. The three-layered scheme allows us to study a larger system more accurately than the previously proposed two-layered schemes IMOMO, which can treat a medium size system very accurately, and IMOMM, which can handle a very large system with modest accuracy. This three-layered scheme has been applied to activation barriers for the Diels−Alder reaction of acrolein + isoprene, acrolein + 2-tert-butyl-1,3-butadiene, and ethylene + 1,4-di-tert-butyl-1,3-butadiene. In general, the results for b...

ONIOM: A Multilayered Integrated MO + MM Method for Geometry Optimizations and Single Point Energy Predictions. A Test for Diels−Alder Reactions and Pt(P(t-Bu)3)2 + H2 Oxidative Addition

Heterotrinuclear Pt2Ag Clusters with Pt-Ag Bonds Unsupported by Covalent Bridges. Molecular Structures of (NBu4)2(Pt2(μ-Cl)2(C6F5)4) and (NBu4)(Pt2AgCl2(C6F5)4O(C2H5)2).

XPd(μ-dppm) 2 Pt(C 6 F 5 ) (X = Cl ( I ), Br ( II )) have been prepared by reacting Pd 2 (dba) 3 ·CHCl 3 and PtX- (C 6 F 5 )(η 1 -dppm) 2 . Reaction of complex I with SnCl 2 gives the SnCl 3 − derivative, whilst ligands L (PPh 3 , P(OPh) 3 , SbPh 3 ) render the cationic complexes. The species R 2 N + , SO 2 or MeOOC)CCCOOMe insert into the PdPt bond of I to give A-frame Pd(II)- Pt(II) complexes. The reactions of CIPd(μ-dppm) 2 - Pt(C6F 5 ) with isonitriles CNR (R = p -Tol, Cy) lead to products containing either terminal or inserted isocyanide or both.

Synthesis and Reactivity of Mixed Pentafluorophenyl Platinum(I)-Palladium(I) Derivatives.

The synthesis of [ClPt(µ-dppm)2Pt(C6F5)](1)(dppm = Ph2PCH2PPh2) is described. The Cl ligand in (1) can be replaced by Br, SCN and by neutral ligands (PPh3, AsPh3, pyridine, or CO) to give other PtI complexes. MeO2CCCCO2Me, SO2, [N2C6H4Me-p]+, and H+ insert into the Pt–Pt bond to give A-frame PtII complexes. SnCl2, on the contrary, inserts into the Pt–Cl bond to give Pt–SnCl3 derivatives. t-Butyl isocyanide acts as do other neutral ligands to give cationic complexes [(ButNC)Pt(µ-dppm)2Pt(C6F5)]+, whereas CNC6H11 and CNC6H4Me-p lead to insertion, coordination, or both depending on the conditions of the reaction. The products are characterized by i.r. and 1H, 19F, and 31P n.m.r. spectroscopy.

Synthesis and Reactivity of Neutral and Cationic Pentafluorophenyl Platinum(I) Derivatives.

Bi- and Trinuclear PtAg Complexes with or Without Pt-Ag Bonds. Molecular Structure of (PPh3(C6Cl5)ClPt(μ-Cl)AgPPh3).

Synthesis of cationic palladium(ii) and platinum(ii) complexes with a monodentate trialkylphosphoniumdithiocarboxylate ligand: molecular structure of σ-pentafluorophenylbis(triethylphosphine)(triethylphosphoniodithioformato# -s)pallad

Juan Forniés

Papers

Heterotrinuclear Pt2Ag Clusters with Pt-Ag Bonds Unsupported by Covalent Bridges. Molecular Structures of (NBu4)2(Pt2(μ-Cl)2(C6F5)4) and (NBu4)(Pt2AgCl2(C6F5)4O(C2H5)2).

Synthesis and Reactivity of Mixed Pentafluorophenyl Platinum(I)-Palladium(I) Derivatives.

Synthesis and Reactivity of Neutral and Cationic Pentafluorophenyl Platinum(I) Derivatives.

Bi- and Trinuclear PtAg Complexes with or Without Pt-Ag Bonds. Molecular Structure of (PPh3(C6Cl5)ClPt(μ-Cl)AgPPh3).

Synthesis of cationic palladium(ii) and platinum(ii) complexes with a monodentate trialkylphosphoniumdithiocarboxylate ligand: molecular structure of σ-pentafluorophenylbis(triethylphosphine)(triethylphosphoniodithioformato# -s)pallad