-Alkylation of organonitrogen compounds catalyzed by methylene-linked bis-NHC half-sandwich ruthenium complexes.

An efficient ruthenium-catalyzed -alkylation of amines, amides and sulfonamides has been developed employing novel pentamethylcyclopentadienylruthenium(II) complexes bearing the methylene linked bis(NHC) ligand bis(3-methylimidazol-2-ylidene)methane. The acetonitrile complex 2 has proven particularly effective with a broad range of substrates with low catalyst loading (0.1-2.

Evolutionary drivers of group foraging: A new framework for investigating variance in food intake and reproduction.

A proposed fundamental driver of group living is more reliable, predictable foraging and reproduction, i.e., reduced variance in food intake and reproductive output.

First examples of neutral and cationic indenyl nickel(II) complexes bearing arsine or stibine ligands: highly active catalysts for the oligomerisation of styrene.

New indenyl nickel(ii) complexes bearing arsine or stibine ligands synthesised by a new methodology exhibit very high catalytic activities for the oligomerisation of styrene.

Counteranion and solvent assistance in ruthenium-mediated alkyne to vinylidene isomerizations.

The complex [Cp*RuCl((i)Pr2PNHPy)] (1) reacts with 1-alkynes HC≡CR (R = COOMe, C6H4CF3) in dichloromethane furnishing the corresponding vinylidene complexes [Cp*Ru═C═CHR((i)Pr2PNHPy)]Cl (R = COOMe (2a-Cl), C6H4CF3 (2b-Cl)), whereas reaction of 1 with NaBPh4 in MeOH followed by addition of HC≡CR (R = COOMe, C6H4CF3) yields the metastable π-alkyne complexes [Cp*Ru(η(2)-HC≡CR)((i)Pr2PNHPy)][BPh4] (R = COOMe (3a-BPh4), C6H4CF3 (3b-BPh4)). The transformation of 3a-BPh4/3b-BPh4 into their respective vinylidene isomers in dichloromethane is very slow and requires hours to its completion. However, this process is accelerated by addition of LiCl in methanol solution.

Facile O-H bond activation in alcohols by [Cp*RuCl((I)Pr2PSX)] (X = pyridyl, quinolyl): a route to ruthenium(IV) hydrido(alkoxo) derivatives.

The complexes [Cp*RuCl((i)Pr(2)PSX)] (X = pyridyl, quinolyl) react directly with alcohols ROH (R = Me, Et, (i)Pr, (n)Pr) and NaBPh(4), affording the novel cationic hydrido(alkoxo) derivatives [Cp*RuH(OR)((i)Pr(2)PSX)][BPh(4)]. These ruthenium(IV) compounds result from the formal oxidative addition of the alcohol to the 16-electron fragment {[Cp*Ru((i)Pr(2)PSX)](+)}, generated in situ upon chloride dissociation. The hydrido(alkoxo) complexes are reversibly deprotonated by a strong base such as KOBu(t), yielding the neutral alkoxides [Cp*Ru(OR)((i)Pr(2)PSX)], which are remarkably stable toward β elimination and do not generate the corresponding hydrides.

Proton-transfer reactions to half-sandwich ruthenium trihydride complexes bearing hemilabile P,N ligands: experimental and density functional theory studies.

The trihydride complexes [Cp*RuH(3)(kappa(1)-P-(i)Pr(2)PCH(2)X)] [X = pyridine (Py), 2a; quinoline (Quin), 2b] have been prepared by reaction of the corresponding chloro derivatives [Cp*RuCl(kappa(2)-P,N-(i)Pr(2)PCH(2)X)] [X = Py (1a), Quin (1b)] with NaBH(4) in methanol. Both 2a and 2b exhibit quantum-mechanical exchange coupling. The proton-transfer reactions to 2a and 2b using strong as well as weak proton donors have been experimentally and computationally studied.

Oligomerization of styrenes mediated by cationic allyl nickel complexes containing triphenylstibine or triphenylarsine.

The cationic complexes [Ni(eta(3)-CH(2)C(R)CH(2))(SbPh(3))(3)][BAr'(4)] (R = CH(3), H ; Ar' = 3,5-C(6)H(3)(CF(3))(2)), [Ni(eta(3)-CH(2)C(R)CH(2))(AsPh(3))(2)][BAr'(4)] (R = CH(3), H ), [Ni(eta(3)-CH(2)CHCH(2))(PPh(3))(L)][BAr'(4)] (L = SbPh(3), AsPh(3)), and the neutral derivatives [Ni(eta(3)-CH(2)C(R)CH(2))Br(L)] (L = SbPh(3), R = CH(3), H ; L = AsPh(3), R = CH(3), H ) have been prepared and characterized. The X-ray crystal structures of , , , and have been determined. These complexes are very active catalyst precursors for the low-molecular weight oligomerization of RC(6)H(4)CH[double bond, length as m-dash]CH(2) to mainly dimers and trimers of styrene (R = H) or 4-methylstyrene (R = CH(3)).

Oligomerization and regioselective hydrosilylation of styrenes catalyzed by cationic allyl nickel complexes bearing allylphosphine ligands.

The complexes [Ni(eta(3)-CH(2)CHCH(2))Br(kappa(1)P-PR(2)CH(2)CH=CH(2))] (R = Ph 1, (i)Pr2 ) and [Ni(eta(3)-CH(2)C(R')CH(2))(kappa(1)P-PR(2)CH(2)CH=CH(2))(2)][BAr'(4)] (R' = H, R = Ph 4a, R = (i)Pr 4b; R' = CH(3), R = Ph 5a, R = (i)Pr 5b; Ar' = 3,5-C(6)H(3)(CF(3))(2)) have been prepared and characterized. The X-ray crystal structures of 1, 2 and 5b have been determined. 4a-b and 5a-b are catalyst precursors for the oligomerization of RC(6)H(4)CH=CH(2) to oligostyrene (R = H) or oligo(4-methylstyrene) (R = CH(3)) respectively, without the need of a co-catalyst such as methylalumoxane.

Half-sandwich hydride complexes of ruthenium with bidentate phosphinoamine ligands: proton-transfer reactions to [(C5R5)RuH(L)] [R = H, Me; L = dippae, (R,R)-dippach].

The complexes [(C5R5)RuH(dippae)] [R = H (1a), Me (2a); dippae = 1,2-bis(diisopropylphosphinoamino)ethane] and [(C5R5)RuH((R,R)-dippach)] [R = H (1b), Me (2b); (R,R)-dippach = (R,R)-1,2-bis(diisopropylphosphinoamino)cyclohexane] have been prepared and characterized. The cationic ruthenium(IV) dihydride derivatives [(C5R5)RuH2(dippae)][BPh4] [R = H (3a), Me (4a)] and [(C5R5)RuH2((R,R)-dippach)][BPh4] [R = H (3b), Me (4b)] are also reported. No significant intramolecular interaction between the amino protons and the hydrogen atoms bound to the metal has been observed in any of these compounds.

[Ni(eta 3-CH2C(CH3)CH2)(SbPh3)3][BAr'4]: an extremely active cationic allyl nickel-stibine catalyst for the oligomerization of styrene.

The pseudotetrahedral, formally 5-coordinate complex [Ni(eta 3-CH2C(CH3)CH2)(SbPh3)3][BAr'4] (Ar' = 3,5-C6H3(CF3)2) as well as the 4-coordinate derivative [Ni(eta 3-CH2C(CH3)CH2)(AsPh3)2][BAr'4] act as extremely efficient catalysts for the oligomerization of styrene.