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Showing papers in "Chemical Reviews in 1988"



Journal ArticleDOI

2,580 citations


Journal ArticleDOI
TL;DR: The concept of van der surface thermodynamics of (Lewis) Waals was first proposed by as discussed by the authors to account for certain properties of acid-base (AB) Interactions nonideal gases and liquids.
Abstract: The concept of a general attractive interaction between neutral atoms was first proposed by van der Surface Thermodynamics of (Lewis) Waals in 1873, to account for certain properties of Acid-Base (AB) Interactions nonideal gases and liquids.’ Three different but nevThe Young-Dupr6 Equation 933 ertheless related phenomena were subsequently shown to contribute to these “van der Waals” interactions: (1) randomly orienting dipole-dipole (or orientation) inPositive and Negative Interfacial

2,210 citations



Journal ArticleDOI

1,014 citations



Journal ArticleDOI
TL;DR: Schore as mentioned in this paper was a member of the faculty at the University of California, Los Angeles and was named recipient of the Magnar Ronning Award for Excellence in Teaching in 1979, and Camille and Henry Dreyfus Teacher-Scholar fw 1981-1986.
Abstract: 0009-2685/88/078&1081$06.50/0 Neil E. Schore was born in Newark. NJ. in 1948. He attended schools In Bronx, NY. and Ridgefield. NJ. and received his B.A. degree in chemistry from the University of Pennsylvania in 1969. He returned to New York to do graduate work at Columbia UnivwsRy under the direction of Nicholas J. TWO. completing the Ph.0. in 1973. Cai Tech was the next stop, fw 2'1, years as a National InsfRutes of Health Postdoctoral Fellow in the labwatwks of Robert G. Bergman, where he discovered the existence of wganometailic chemistry. Since 1976 he has been a member of the faculty at the University of California. Davis. He was named recipient of the Magnar Ronning Award for Excellence in Teaching in 1979, and Camille and Henry Dreyfus Teacher-Scholar fw 1981-1986. HIS research interests involve mechanistic and synthetic lransitionmetal chemistry. including study 01 early transaion-metal systems with remote ligand sites. construction and chemistry of biand polymetallic complexes. and applications 01 ths chemisby of these systems to natural pcducts synthesis. A special area of emphasis has been the study of the Pauson-Khand cyciopentenone synthesis

815 citations











Journal ArticleDOI
TL;DR: In this paper, the authors discuss recent research into the preparation, characterization, and reactivity of two-carbon fragments (i.e., alkynes and alkenes) bound to a single group 4 (Ti, Zr, Hf) metal center.
Abstract: Transition metals have the ability to stabilize highly reactive organic fragments and also to activate stable molecules toward selective attack. A large number of transition-metal complexes of small organic molecules have been prepared, but syntheses of such species are frequently limited to a specific type of organic fragment bound to a particular metal system. Few general strategies lend themselves to the preparation of a wide variety of fragments bound to a specific metal or to a particular fragment bound to a wide variety of metals. As a result, few structure-reactivity relationships have been mapped in organometallic chemistry. This paper will discuss recent research into the preparation, characterization, and reactivity of two-carbon fragments (i.e., alkynes and alkenes) bound to a single group 4 (Ti, Zr, Hf) metal center, in the hope that the initial outlines of such structure-reactivity relationships will be discernible. Of the many transition-metal complexes of alkynes, alkenes, aldehydes, and ketones which have been prepared, relatively few involve group 4 metals. Strategies for the preparation of later transition-metal complexes of such molecules usually involve the direct combination of the unsaturated organic fragment and a coordinatively unsaturated metal center. However, low-valent, coordinatively unsaturated group 4 species are unstable and difficult to prepare. When such metal centers bind alkynes, alkenes, or thioaldehydes, the high degree of x-back-bonding from the metal to the organic fragment often makes the resulting complex behave more like a metallacyclopropene, metallacyclopropane, or metallathiirane. These complexes have been studied for a number of reasons, including intrinsic interest in their structure and reactivity, the desire to model catalytic processes such as Fischer-Tropsch chemistry and hydrogenation, and because such species may be of practical use as vehicles for olefin and acetylene polymerization and for achieving selective transformations of use in organic synthesis.

Journal ArticleDOI
TL;DR: The first metal carbonyl compounds of this type that could be isolated were MC1(FBF3)(NH=NR)(CO)(PPh3)2 (M = Ru, OS),^ R~(CO)F8 however, examples are known in which in spite of electronic unsaturation of the metal, the anion remains uncoordinated as mentioned in this paper.
Abstract: Organometallic compounds of weakly coordinating anions, e.g., BF4-, PF,, AsF;, and SbF6-, have been the object of many studies in recent years. These complexes contain a hard anion coordinated to a soft metal center in a low oxidation state with a-acceptor ligands (e.g., CO, PR3).l They are highly reactive; the anions are excellent leaving groups and can easily be replaced by other ligands under very mild conditions, so they have proven to be useful starting materials in preparative organometallic synthesis. The first metal carbonyl compounds of this type that could be isolated were MC1(FBF3)(NH=NR)(CO)(PPh3)2 (M = Ru, OS),^ R~(CO)F8 however, examples are known in which in spite of electronic unsaturation of the metal, the anion remains uncoordinated [e.g., [Rh(PPh3)3]+9@’ or [CO(P(OR)~)~]+PF~;~~ also in Cu(CO)(AsF6) the anion is apparently not coordinated to the metal, in contrast to the corresponding sulfonato complexes”]. The cationic fragment in these complexes must have low-lying acceptor orbitals as was shown for the ds M(C0)5 fragment.12a A theoretical investigation of the [CpzZrC1]* moiety showed two low-lying 6and a-acceptor MOs.lZb It appears that the more acidic the corresponding hydrides L,MH are, the lower are the LUMOs and the higher is the electrophilicity of ML,+. There are many such complexes of metals in “normal” oxidation states which can only be mentioned briefly here. Examples include M(N-vinylimidaz~le)~SiF~ (M = Mn, Fe, Co, Ni, Cu, Zn), [ N ~ ( ~ I I ) ~ ( H ~ O ) B F ~ ] B F ~ , C U ( P P ~ ~ ) ~ B F ~ , and Mn(2,g-lutidine N-oxide) (F) (BF4).I3 Often the anions BF4and C104occur as bridging or “semicoordinating” ligands.14











Journal ArticleDOI
TL;DR: The intramolecular enonmlefin photocycloaddition was first reported by Ciamician in 1908 when he observed the formation of carvone camphor on prolonged exposure to Italian sunlight.
Abstract: The intramolecular enonmlefin photocycloaddition, the light-induced [2+2] cycloaddition of a ground-state olefin tethered to an excited-state enone to form a cyclobutane, was first reported by Ciamician in 1908 when he observed the formation of carvone camphor on prolonged exposure of carvone to \"Italian sunlight\"' (Figure 1). Buchi's reinvestigation of this process confirmed the isomerization and sparked new interest in the reaction? The rapidity with which complex systems could be constructed by this method was recognized by Cookson3 who irradiated the Diels-Alder adduct of quinone and cyclopentadiene and by Eaton' who utilized a similar intramolecular photocycloaddition in his synthesis of cuhane. This reaction was first applied to the total synthesis of a natural product by Wiesner who prepared 12-epilycopodine utilizing an intramolecular photocycloaddition5 (Figure 2). Corey: Eaton,' and de May0,8.~ among others, subsequently began to investigate the intermolecular enone-olefin photocycloaddition, and these studies culminated in several successful synthetic applications, including the synthesis of caryophyllene'O and bourbonene,'l as well as a proposed mechanistic rationale for the reaction. While the major disadvantage of the intermolecular photocycloaddition is its low regioselectivity in some systems, this problem can be substantially overcome by incorporating the olefin and the enone in the same molecule. Although many of the early examples of the reaction were intramolecular, this variation saw only limited use until the late 1970s when its potential for the rapid construction of systems of