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

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

N-Heterocyclic Carbenes in Late Transition Metal Catalysis

The fascinating story of olefin (or alkene) metathesis (eq
1) began almost five decades ago, when Anderson and
Merckling reported the first carbon-carbon double-bond
rearrangement reaction in the titanium-catalyzed polymerization of norbornene. Nine years later, Banks and Bailey reported “a new disproportionation reaction . . . in which olefins are converted to homologues of shorter and longer carbon chains...”. In 1967, Calderon and co-workers named this metal-catalyzed redistribution of carbon-carbon double bonds olefin metathesis, from the Greek word “μeτάθeση”, which means change of position. These contributions have since served as the foundation for an amazing research field, and olefin metathesis currently represents a powerful transformation in chemical synthesis, attracting a vast amount of interest both in industry and academia.

https://core.ac.uk/download/pdf/4884240.pdf

Ruthenium-based heterocyclic carbene-coordinated olefin metathesis catalysts.

The Golden Age of Transfer Hydrogenation

The vast family of ruthenium complexes with nucleophilic N-heterocyclic carbene (NHC) ligands is selectively discussed as an improved alternative to their parent diphosphane ruthenium counterparts previously applied in olefin metathesis reactions. The survey covers work done to-date on the ruthenium alkylidene, vinylidene, allenylidene and indenylidene complexes bearing imidazolin-2-ylidene and dihydroimidazolin-2-ylidene carbenes, as well as a number of immobilised ruthenium complexes having these types of ligands. Examples of chiral compounds complete the spectrum of NHC ruthenium complexes. Synthetic methods, catalytic properties and application profile in ring-closing metathesis, cross metathesis, ring-opening metathesis and metathesis polymerisation are highlighted.

https://technology.matthey.com/wp-content/uploads/pdf/123-137-pmr-jul05.pdf

Ruthenium Complexes Bearing N-Heterocyclic Carbene (NHC) Ligands HIGHLY EFFICIENT METATHESIS PRE-CATALYSTS WITH ENHANCED ACTIVITY AND SELECTIVITY

The paper presents recent work conducted in our group on the synthesis of a novel class of homogeneous and immobilized Ru- complexes containing Schiff bases as O,N-bidentate ligands benefiting from a versatile, quite general and thoroughly exemplified two- step procedure. The new Ru-complexes with improved stability incorporate a variety of Schiff bases, associated with traditional inorganic and organic ligands such as chloride, phosphanes, arenes, cyclodienes, NHC etc., and different carbenes (alkylidene, vinylidene, allenylidene and indenylidene). By a proper choice of the Schiff base, useful physical and chemical properties of the derived Ru- complexes could be induced resulting in tunable catalytic activity for metathesis and related processes. A pertinent example is the latency of selected Schiff base Ru catalysts which by becoming active only under specific conditions (heat or acid activation) are ideal for industrial applications, e.g. reaction injection molding processes. The synthetic approaches that are critically discussed in this artcile have led to a diversity of Ru-complexes of which several members have risen to the rank of commercial catalysts.

Ruthenium Complexes Containing Bidentate Schiff Base Ligands as Precursors of Homogeneous and Immobilized Catalysts

Ruthenium Vinylidene Complexes SYNTHESES AND APPLICATIONS IN METATHESIS CATALYSIS

This paper surveys the latest and fast growing developments in the design and synthesis of homogeneous and immobilized ruthenium metathesis catalysts. These novel ruthenium carbene complexes, devised as convenient counterparts of the well-defined tungsten and molybdenum alkylidene complexes, display comparable activity and selectivity in metathesis reactions combined with good tolerance towards organic functionalities, air and moisture. Due to their valuable attributes, they have been applied successfully in a multitude of complex organic and polymer syntheses involving ring-opening and ring-closing metathesis reactions, cross- metathesis, enyne metathesis and ring-opening metathesis polymerization.

Recent Developments in Design and Synthesis of Well‐Defined Ruthenium Metathesis Catalysts— A Highly Successful Opening for Intricate Organic Synthesis

A two step procedure for the synthesis of a novel family of homogeneous and immobilized Ru-complexes containing Schiff bases as O,N-bidentate ligands is described. The new Ru-complexes have been structurally characterized by IR, Raman,1H-,13C-NMR spectroscopy. The Schiff bases were associated with a diversity of inorganic and organic ligands such as chloride, phosphane, arenes, various carbenes (alkylidene, vinylidene, indenylidene and allenylidene as well as N-heterocyclic carbenes) and cyclodienes. By choosing a selective range of substituents for the Schiff base, useful physical and chemical properties of the prepared Rucomplexes can be induced. This synthetic approach is promising in creating a valuable and diverse selection of Ru-complexes, valuable for future applications.

Valerian Dragutan

Papers

Ruthenium Complexes Bearing N-Heterocyclic Carbene (NHC) Ligands HIGHLY EFFICIENT METATHESIS PRE-CATALYSTS WITH ENHANCED ACTIVITY AND SELECTIVITY

Ruthenium Complexes Containing Bidentate Schiff Base Ligands as Precursors of Homogeneous and Immobilized Catalysts

Ruthenium Vinylidene Complexes SYNTHESES AND APPLICATIONS IN METATHESIS CATALYSIS

Recent Developments in Design and Synthesis of Well‐Defined Ruthenium Metathesis Catalysts— A Highly Successful Opening for Intricate Organic Synthesis

Rational Design and Convenient Synthesis of a Novel Family of Ruthenium Complexes with O,N‐Bidentate Ligands