ライフサイエンスコーパス: sigma bond

1 of halogen bond acceptors (lone pair, pi and sigma bonds).

2 alpha-substituent centers (A-B) is only the sigma bond.

3 the nucleophile to the backside of the C--Cl sigma bond.

4 ple of the protonation of an element-element sigma bond.

5 over-limiting C=C/CC insertion into the An-N sigma-bond.

6 ith either the aromatic pi-system or the C H sigma-bond.

7 e Sn-Sn-C angles which may shorten the Sn-Sn sigma-bond.

8 the acceptor is reduced by one carbon-carbon sigma-bond.

9 which contain two-center, two-electron Ln-B sigma bonds.

10 alizations, result in the cleavage of strong sigma bonds.

11 are the first iron-sulfur clusters with Fe-C sigma bonds.

12 ctroscopy, they readily couple to form final sigma bonds.

13 good lone pair electron donor toward geminal sigma bonds.

14 ly simple electronic structure of just Si-Si sigma bonds.

15 dization tendencies that yield the strongest sigma-bonds.

16 space in a bonding way, but do not form full sigma-bonds.

17 lities into lanthanide-alkyl and -heteroatom sigma-bonds.

18 -H, N-H, O-H, C-C, C-N, and C-F, among other sigma-bonds.

19 hypervalent 4-center 6-electron S...S-S...S sigma-bonds.

20 traps represent one-electron intermolecular sigma-bonds.

21 makes Kalpha RIXS a more sensitive probe of sigma-bonding.

22 d state via a series of zinc-pi (1) and zinc-sigma-bonded (2) bridging interactions.

23 ations, can be described by two horizontally sigma-bonded 2p(x) and 2p(y) orbitals along with one per

24 NMR chemical shift calculations support the sigma-bonded 9 as the global minimum.

25 by quinoline-directed, rhodium-catalyzed C-C sigma bond activation.

26 Carbon-carbon sigma-bond activation is a contemporary challenge for or

27 acceptor E-E bond (E = S, Se, and Te) whose sigma bond already has its bond pair electrons.

28 d changed polarity of the phenyl-substituent sigma bond alter the interaction (the Wheeler-Houk pictu

29 ylate by a monodentate terphenyl forms a M-C sigma bond and creates a coordination unsaturation at th

30 nating peripheral bonds, with a weak central sigma bond and significant diradical character.

31 oiety converts the nitrogen lone pair into a sigma bond and the HOMO into a lower-lying orbital that

32 stable electrical contact between the Si-Si sigma bond and the other electrode.

33 ecules the orbital corresponding to the Re-H sigma bond and the Re-H vibrational mode is very localiz

34 e molecule shows that a rearrangement to one sigma bond and two lone pairs on sulfur is usually more

35 on as a triple bond consisting of a covalent sigma bond and two strong pi back-donations.

36 incorporation in 3 and 4 involves tin-carbon sigma bonding and is shown to be fully reversible under

37 cell in this regard: no fewer than three new sigma bonds and a new ring system are formed from simple

38 Gd13Fe10C13 build a picture of covalent Fe-C sigma bonds and conjugated pi systems for which Lewis st

39 talytic aminoboration of C-C pi bonds by B-N sigma bonds and its application to the synthesis of 3-bo

40 ge-bearing units that are doubly linked by 4-sigma-bond and by 6-sigma-bond saturated bridges are com

41 e nonclassical, implicating the dominance of sigma-bonding and absence of pi-back-bonding.

42 The combination of axial trans sigma-bonding and pi-bonding effects that include expans

43 containing both alkene pi-bonds and allylic sigma-bonds, and the ene yields are higher with 1 than w

44 Sigma-bonded arrays are compared to conventional pi-bond

45 The six-coordinate nitrosyl sigma-bonded aryl(iron) and -(ruthenium) porphyrin compl

46 Enhancement of acceptor ability of C-X sigma bonds as one moves from left to right in periods p

47 ion and activation of apolar or weakly polar sigma-bonds at copper using chelating assistance.

48 This simple picture of acceptor ability of sigma bonds being controlled by electronegativity in per

49 s S = 1 and 2) by two strong pi and a strong sigma bond between Fe(IV) and the oxo ligand.

50 resulting in formation of a direct covalent sigma bond between the carbon backbone and the gold meta

51 drazones that allows for the generation of a sigma bond between two unfunctionalized sp(3) carbons in

52 n the two Fe atoms, a bridging sulfur, and d(sigma)-bonding between Fe centers.

53 y differ by the presence or absence of a C-C sigma-bond between the unpaired electrons of the parent

54 perreduced Pt(pop-BF2)(6-) a very rare 6p(2) sigma-bonded binuclear complex.

55 aphite transition owing to the similarity of sigma-bond breakage into a delocalized pi-system.

56 ane(6) (4) with LiNaph/THF establishes a B-B sigma bond but can be accompanied by substituent redistr

57 volves in the intramolecular cleavage of two sigma-bonds (C-O and C-C) and inter/intramolecular const

58 In general, relative donor abilities of sigma bonds can be changed by their through-bond communi

59 As a result, the acceptor ability of sigma bonds can be significantly modified by substitutio

60 anium contribution to the U horizontal lineC sigma-bond can increase from ca. 18 to 32% and within th

61 e to gain better knowledge regarding the way sigma-bonds can be activated by copper to help further d

62 strate that the strong donor ability of C-Ge sigma-bonds can be used to raise the energy of the ancho

63 and subsequently undergo phosphate-sugar O-C sigma bond cleavage, it is highly unlikely (in contrast

64 =O pi orbital and induce phosphate-sugar O-C sigma bond cleavages if the phosphate groups are rendere

65 iers leading to fluxional structures between sigma-bonded configurations or sigma- and pi-bonded conf

66 are the methodologies centered on C(1)-C(2) sigma-bond construction and C(2)-R/Ar bond-forming proce

67 lated by a combination of sigma hole and n-->sigma* bonding contributions with retention of the octet

68 By contrast, only weaker sp(2)-sp(2) sigma bonds could form in unobserved concerted transitio

69 lding a standard enthalpy of formation of di-sigma bonded cyclohexene on Pt(111) at low coverages of

70 At 100 K, cyclohexene adsorbs as intact di-sigma bonded cyclohexene on Pt(111), and the heat of ads

71 lve the activation of apolar or weakly polar sigma-bonds (E-H and E-E' bonds, with E = C, B, Si, Sn,

72 H2 to a metal center via polarization of its sigma bond electron density, known as a Kubas complex, i

73 Di-sigma-bonded ethene and pi-bonded ethene on the clusters

74 Di-sigma-bonded ethylene reacts with carbene species, forme

75 theory calculations, indicate that a single sigma-bond exists between the M(III) centers and the oxo

76 array of p orbitals arranged tangentially in sigma-bonding fashion.

77 pounds with up to four rotationally hindered sigma bonds, for which a single stereoisomer out of seve

78 inct pathway for oxyboration that avoids B-O sigma bond formation and enables this catalyst-free rout

79 electrophilic cyclization, as opposed to S-B sigma bond formation, providing a mechanistically distin

80 ition states (TSs) are early with respect to sigma bond formation.

81 pi-MO of 3 that is primarily responsible for sigma-bond formation in 4, not the terminal allenyl pi-b

82 alpha-carbon occurs concomitantly with C-Pd sigma-bond formation.

83 cking pancake multicenter bond formation and sigma-bond formation.

84 The sigma-bond formed in this process corresponds to the pro

85 e B-H sigma-bond is broken in favor of a B-C sigma-bond, forming Cp*W(CO)(2)(H)(C(5)H(11)-Bpin), a tu

86 The review ends with speculation that sigma-bond-forming reactions may also be observed someda

87 g to three rings, almost never engage in new sigma-bond-forming reactions.

88 ed by two Kekule structures sharing a common sigma bond framework, the square Al(4)(2-) structure has

89 the triflate moiety is channeled through the sigma-bond framework of 1, providing direct access to th

90 es (four lone pairs) and features homoatomic sigma-bond heterolysis, thereby combining the key featur

91 trogen atoms that are separated by only four sigma bonds if its nitrogens were planar.

92 y involves concerted addition of 5b across a sigma bond in 14b via 35.

93 rongly M-Cl sigma antibonding and weakly M-M sigma bonding in character.

94 The acceptor ability of the C-X sigma bonds in monosubstituted ethanes increases when go

95 lar magnitude influences acceptor ability of sigma bonds in monosubstituted ethenes in a complex way.

96 tal evidence agrees with involvement of only sigma bonds in these transformations.

97 the opportunity that exists to form sp-sp(2) sigma bonds in transition structures 21 and 23 that lead

98 re transfer of the first electron from a C-H sigma-bond in methane to one of the metal centers.

99 nover-limiting C-C insertion into an M-N(H)R sigma-bond in the transition state.

100 excellent opportunity to study the degree of sigma-bonding in a metalloboratrane as a function of ele

101 The Cu-O sigma-bonds in the mu3-oxo-bridged structure would provi

102 igma-hole is located on the extension of the sigma-bond, in the hypervalent species our DFT calculati

103 rganoiron intermediate, where the subsequent sigma bond insertion of dioxygen into the C-Fe bond comp

104 stem (Ea = 1.1-2.4 kcal/mol) rather than C-C sigma-bond insertion into the cyclopropenyl moiety (Ea =

105 However, the Pt-Pt sigma bonding interaction is limited by the relatively l

106 es of molecules wherein very close C-F---H-C sigma-bond interactions, which we have termed "jousting"

107 ure description for NiSOD(ox) reveals strong sigma-bonding interactions between Ni and the equatorial

108 enue for catalyst regeneration from the Au-C sigma-bond intermediate, in contrast to other Au-catalyz

109 les of vibrational structure in metal-ligand sigma-bond ionizations are observed in the gas-phase pho

110 nd how the concerted scission of the central sigma bond is prevented in the boat conformation.

111 The large 2p character of the azide sigma bonds is responsible for the particularly high N(b

112 are achieved because a covalent Au-C sigma (sigma) bond is formed.

113 In this configuration, the B-H sigma-bond is broken in favor of a B-C sigma-bond, formi

114 ia a diradicaloid transition state where one sigma-bond is made before a second.

115 Y and La and 4f(3) Nd congeners only MIC-->M sigma-bonding is found.

116 rgy required for the interconversion of the "sigma-bonded" isomer into a putative NHC-stabilized disi

117 arbons of opposing aryl groups evolve into a sigma bond leading to the formation of the biaryl anion

118 lexes are regularly isolated with classical, sigma-bonded ligands, and this has been thought to be th

119 nantly ionic, with covalent character in the sigma-bonding Ln-B HOMO.

120 Examples of sigma-bonds made of a single electron delocalized over t

121 ystem of triplet O2, the weakness of the O-O sigma bond makes reactions of O2, which eventually lead

122 en site-pair that cleaves the C-H bond via a sigma bond metathesis reaction, during which the Co inse

123 Similarly, Co clusters also catalyze the sigma bond metathesis step, but much less effectively be

124 oxidative addition/reductive elimination or sigma-bond metathesis are disfavored.

125 The reaction is therefore viewed as a formal sigma-bond metathesis between an N-H bond of ammonia and

126 osed to proceed through hydroalumination and sigma-bond metathesis between the resultant alkenyl alum

127 also shown that on the Au(111) surface this sigma-bond metathesis can be combined with Glaser coupli

128 DFT calculations support a sigma-bond metathesis mechanism during transmetalation a

129 We propose a sigma-bond metathesis mechanism in which an Fe-H interme

130 nd theoretical results support a bimolecular sigma-bond metathesis mechanism in which the phenolic pr

131 tion of tert-butyl acetylene by an insertion/sigma-bond metathesis mechanism involving [((i)Pr(2)-ATI

132 ly exoenergetic (-55 kcal/mol), and reveal a sigma-bond metathesis mechanism to be unfavorable compar

133 cleavage process occurs by a metal-assisted sigma-bond metathesis mechanism to generate a borane com

134 ies easily activates H-H and Si-H bonds by a sigma-bond metathesis mechanism, which was further confi

135 pentane), undergoes C-H bond activation by a sigma-bond metathesis mechanism--in 16 micros, a termina

136 anism is characterized by a rate-determining sigma-bond metathesis of an alkoxide complex with the si

137 erein, we disclose the first examples of the sigma-bond metathesis of silylated alkynes with aromatic

138 reversible for the minor isomer pathway, and sigma-bond metathesis of the metallacycle Ni-O bond with

139 de 1-OSiPh3 apparently via an unconventional sigma-bond metathesis pathway in which the Ni center is

140 ce of H(2) carrier gas was consistent with a sigma-bond metathesis pathway.

141 ly unsaturated metal centres at the SBUs via sigma-bond metathesis pathways and as a result of the st

142 sed in terms of classical and unconventional sigma-bond metathesis pathways.

143 ophile and the metal as nucleophile, mediate sigma-bond metathesis pathways.

144 d nickel metallacycle followed by sequential sigma-bond metathesis processes involving the two Si-H b

145 The sigma-bond metathesis reaction of 13 with Mes2SiH2 yield

146 aining alkene and subsequent silylation by a sigma-bond metathesis reaction, affording the observed p

147 ribution at silicon, and chemoselectivity in sigma-bond metathesis reactions, are discussed.

148 uggest that borylation occurs via successive sigma-bond metathesis steps, whereby a Pt(II) -H interme

149 ssociation of coordinated alkene followed by sigma-bond metathesis to form H2 and Zr-allyl.

150 hen undergoes B-C bond formation by a second sigma-bond metathesis to generate the final functionaliz

151 er ligand is created by a pair of Ar-H/Ta-Me sigma-bond metathesis transformations, rather than by a

152 ism proceeding by hydrocupration followed by sigma-bond metathesis with a hydrosilane.

153 dative addition to H-abstraction and then to sigma-bond metathesis with increasing O-content, as acti

154 e transesterification of vanadate occurs via sigma-bond metathesis, and vanadium enolate is directly

155 -O(ox), cleave C-H bonds heterolytically via sigma-bond metathesis, with Pd(2+) adding to the C-H bon

156 utene and cyclopropane) with Ph(2)SiH(2) via sigma-bond metathesis.

157 tallographically verified, a snapshot of the sigma-bond metathesis.

158 lectron transfer, halogen atom transfer, and sigma-bond methatesis.

159 ma* orbital of E-X as emphasized in the 'n-->sigma*' bonding model.

160 e between chromophores, since rotation about sigma bonds negligibly affects the orbital overlap withi

161 reactions often involve coordination of the sigma bond of dihydrogen, silanes (Si-H), or alkanes (C-

162 acts with H-X (X = H, Si, B, Al, C, N, P, O) sigma bonds of H2, silanes, borane (HBpin, pin = pinacol

163 1a, and the CO2 insertion into the alpha-C-H sigma-bond of amine 1a.

164 irectly exploit the polarized reverse-dative sigma-bond of metal-borane complexes (i.e., M-->BR3 ) re

165 The angles between the three sigma-bonds of the carbon sp(2) orbitals are roughly 120

166 ion of the unsubstituted vertices as well as sigma-bonds of the cluster framework of 4.

167 These studies also show that the C-C sigma bonding orbital of the radical cation contains onl

168 an electron is removed from the Re-H or Re-D sigma-bond orbital.

169 at extension of the MCSCF methods to include sigma bonding orbitals or virtual-orbital CI brings MCSC

170 ctions between Lewis orbitals (predominantly sigma bonding orbitals).

171 l of an electron from the predominantly Re-H sigma-bonding orbitals.

172 with a diatropic ring current following the sigma-bond path formed by Si 3p orbitals.

173 itution" (CEIS) in which the gold(III)-furyl sigma-bond produced by furan auration acts as a nucleoph

174 the chemisorption process involves M[bond]C sigma-bond protonolysis at the strong surface Bronsted a

175 i-intermediate 10 is higher than that of the sigma-bonded reactant 9 by approximately 2 kcal/mol acco

176 i.e. unbridged) cobalt-cobalt three-electron sigma bond, respectively, each with a formal bond order

177 s of reversible beta-hydride elimination and sigma-bond rotation processes that occur following a rar

178 r/intramolecular construction of two/one C-C sigma-bond(s).

179 t are doubly linked by 4-sigma-bond and by 6-sigma-bond saturated bridges are compared with ones havi

180 tracyclic product imply rotations around two sigma bonds (sigma(C-C) and sigma(C-N), bonds beta and a

181 on that activate the C-C pi bond and the B-N sigma bond simultaneously.

182 The consecutive thermal migration of two sigma-bonds (stepwise dyotropic rearrangement) is an exa

183 ) at low coverages of -135 kJ/mol and a C-Pt sigma bond strength of 205 kJ/mol.

184 9.0 kcal/mol), although one of the two tetra-sigma-bonded structures (-26.7 kcal/mol) is similar in e

185 action products indicates that the two tetra-sigma-bonded structures (that are energetically comparab

186 conversion of the [4+2] product to the tetra-sigma-bonded structures entails huge barriers (>37.0 kca

187 dates ([2+2] adduct, [4+2] adduct, two tetra-sigma-bonded structures, and one radical-like structure)

188 ned by three independent delocalized (pi and sigma) bonding systems, each of which satisfies the 4n +

189 erate isomerization (topomerization) of the "sigma-bonded" tautomers of 1H[B(Ar(F))4], which proceeds

190 rder analysis and partitioning reveals 4c-2e sigma bonds that stabilize the two-dimensional structure

191 lectronic properties of the sulfur-methylene sigma bonds that terminate the molecule.

192 nes, that contain strongly interacting Si-Si sigma bonds, the essential components of the bulk semico

193 a single operation, to two new carbon-carbon sigma-bonds, three new stereogenic centers, and two new

194 differences in geometry that reflect pseudo-sigma bonding to the Fe(III) and relate to reactivity.

195 ation reaction, the addition of boron-oxygen sigma bonds to alkynes.

196 For nearly 70 years, the addition of boron-X sigma bonds to carbon-carbon multiple bonds has been emp

197 from neutron diffraction data contains a B-H sigma-bond to iridium with an elongated B-H bond distanc

198 kly pi-bonded on monolayer Ni/Pt(111) but di-sigma-bonded to Pt(111) and Ni(111).

199 Ph, that is pi-bonded to the osmium atom and sigma-bonded to the platinum atom.

200 of copper to promote the addition of apolar sigma-bonds to CC multiple bonds via a 2e redox sequence

201 functionalities of groups 2 to 16 and a few sigma-bonded transition metal complexes are experimental

202 method for generating angular forces around sigma-bonded transition metal ions is generalized to tre

203 al intermediate that readily reacts with N-H sigma bonds under catalytically relevant conditions.

204 sults demonstrate activation of this boron-O sigma bond using a gold catalysis strategy that is funda

205 p-character of orbitals comprising the Sn-Sn sigma-bond when the Sn-Sn-C angle is decreased by ca. 30

206 atoms between graphite layers pair and form sigma-bonds, whereas the nonbridging carbon atoms remain

207 pi-bonds between graphite layers convert to sigma-bonds, whereas the other half remain as pi-bonds i

208 ludes the biomimetic and organometallic Fe-C sigma bond, which enables bidirectional activity reminis

209 B)>Ru metalacycle is formed by two bent B-Ru sigma-bonds with the concomitant increase of the bond or