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Ligand cooperativity provides (transition) metal complexes with new reactivities in substrate activation and catalytic reactions, but usually the ligand acts as an internal (Brønsted) base, while the metal acts as a (Lewis) acid. We describe the synthesis and stepwise activation of a new phosphane-pyridine-amide ligand PNNH2 in combination with RhI. The ligand is susceptible to stepwise proton and hydride loss from the nitrogen arm (imine formation) and deprotonation at the pyridylphosphine arm (dearomatization), giving rise to amine complex 1, amido species 2, imine complex 3 and dearomatized compound 4. Complex 4 bears a dual-mode cooperative PNN′ ligand containing both a (nucleophilic) basic methine fragment and a reactive (electrophilic) imine moiety. The basic ligand arm enables substrate deprotonation while the imine ligand arm enables reversible 'storage' of the activated (nucleophilic) form of a sulfonamide substrate at the ligand. In combination with metal-based reactivity, this allows for the mono-alkylation of o-toluenesulfonamide with iodomethane. Compounds 1, 3 and 4 are structurally characterized. We also report the first structurally characterized example of an aminal in the coordination sphere of rhodium, complex 5, [Rh(CO)( PNN′′)], formed by sequential NH activation of sulfonamide by the dearomatized ligand PNN′ and follow-up nucleophilic attack of anionic sulfonamide onto the imine fragment. [ABSTRACT FROM AUTHOR]

The selective α‐deuteration of α,β‐unsaturated nitriles using the strong base tBuOK or a metal‐ligand cooperative Ru pincer catalyst is described. With D2O as deuterium source and glyme as solvent at 70 °C, tBuOK is an efficient catalyst for deuteration at the α‐C(sp2) position of cinnamonitriles, providing access to a broad range of deuterated derivatives in good to excellent yields and with very high levels of deuterium incorporation. While the tBuOK‐catalysed protocol does not tolerate base‐sensitive functional groups, cinnamonitrile derivatives containing a benzylic bromide or ester moiety were deuterated in excellent yields using Milstein's ruthenium PNN pincer catalyst. Moreover, the activity for H/D exchange of the metal‐ligand cooperative Ru catalyst is found to be significantly higher than that of tBuOK, allowing reactions to proceed well even at room temperature. A mechanistic proposal is put forward that involves deprotonation of the cinnamonitrile α‐CH position when using tBuOK as catalyst, whereas H/D exchange catalysis with the Ru PNN pincer likely proceeds via (reversible) oxa‐Michael addition of D2O. [ABSTRACT FROM AUTHOR]

Abstract: Water addition to α,β‐unsaturated nitriles would give facile access to the β‐hydroxy‐nitriles, which in turn can be hydrogenated to the γ‐amino alcohols. We have previously shown that alcohols readily add in 1,4‐fashion to these substrates using Milstein's Ru(PNN) pincer complex as catalyst. However, attempted water addition to α,β‐unsaturated nitriles gave the 3‐hydroxynitriles in mediocre yields. On the other hand, addition of benzyl alcohol proceeded in excellent yields for a variety of β‐substituted unsaturated nitriles. Subsequent treatment of the benzyl alcohol addition products with TMSCl/FeCl3 resulted in the formation of 3‐hydroxy‐alkylnitriles. The 3‐benzyloxy‐alkylnitriles obtained from oxa‐Michael addition also could be hydrogenated directly in the presence of acid to give the amino alcohols as their HCl salts in excellent yields. Hydrogenation under neutral conditions gave a mixture of the secondary and tertiary amines. Hydrogenation in the presence of base and Boc‐anhydride gave the orthogonally bis‐protected amino alcohols, in which the benzyl ether can subsequently be cleaved to yield Boc‐protected amino alcohols. Thus, a variety of molecular scaffolds with a 1,3‐relationship between O‐ and N‐functional group is accessible starting from oxa‐Michael addition of benzyl alcohol to α,β‐unsaturated nitriles. [ABSTRACT FROM AUTHOR]

The Yin – Yang symbol. on the cover symbolizes the complementary nucleophilic and electrophilic ligand arms of the new cooperative PNN pincer ligand, strengthened by the two Kung ‐ Fu fighters making balancing, harmonizing moves. For more details see the Full Paper by J. I. van der Vlugt, B. de Bruin et al. on page 12683 ff. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue is the group of Bas de Bruin and Jarl Ivar van der Vlugt at the University of Amsterdam. The image depicts the complementary nucleophilic and electrophilic ligand arms of a new cooperative PNN pincer ligand. Read the full text of the article at . [ABSTRACT FROM AUTHOR]

The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of α,β-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good yields and high enantiomeric excess. The synthetic utility of the products is demonstrated through stereospecific transformations into multifunctional optically active compounds. [ABSTRACT FROM AUTHOR]

The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of α,β-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good yields and high enantiomeric excess. The synthetic utility of the products is demonstrated through stereospecific transformations into multifunctional optically active compounds. [ABSTRACT FROM AUTHOR]

The [Ru(CO)H(PNN)] pincer complex based on a dearomatised PNN ligand (PNN: 2-di- tert-butylphosphinomethyl-6-diethylaminomethylpyridine) was examined for its ability to isomerise alkenes. The isomerisation reaction proceeded under mild conditions after activation of the complex with alcohols. Variable-temperature (VT) NMR experiments to investigate the role of the alcohol in the mechanism lend credence to the hypothesis that the first step involves the formation of a rearomatised alkoxide complex. In this complex, the hemilabile diethylamino side-arm can dissociate, allowing alkene binding cis to the hydride, enabling insertion of the alkene into the metal-hydride bond, whereas in the parent complex only trans binding is possible. During this study, a new uncommon Ru0 coordination complex was also characterised. The scope of the alkene isomerisation reaction was examined. [ABSTRACT FROM AUTHOR]

Inexpensive and readily available organomagnesium reagents were used for the catalytic enantioselective alkylation of enolizable N-sulfonyl ketimines. The low reactivity and competing enolization of the ketimines was overcome by the use of a copper-phosphine chiral catalyst, which also rendered the transformation highly chemoselective and enantioselective for a broad range of ketimine substrates. [ABSTRACT FROM AUTHOR]

Inexpensive and readily available organomagnesium reagents were used for the catalytic enantioselective alkylation of enolizable N-sulfonyl ketimines. The low reactivity and competing enolization of the ketimines was overcome by the use of a copper-phosphine chiral catalyst, which also rendered the transformation highly chemoselective and enantioselective for a broad range of ketimine substrates. [ABSTRACT FROM AUTHOR]

The catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed direct synthesis of symmetric biaryl compounds from aryl halides in the presence of tBuLi is described. In situ lithium-halogen exchange generates the corresponding aryl lithium reagent, which undergoes a homocoupling reaction with a second molecule of the aryl halide in the presence of the palladium catalyst (1 mol %). The reaction takes place at room temperature, is fast (1 h), and affords the corresponding biaryl compounds in good to excellent yields. The application of the method is demonstrated in an efficient asymmetric total synthesis of mastigophorene A. The chiral biaryl axis is constructed with an atropselectivity of 9:1 owing to catalyst-induced remote point-to-axial chirality transfer. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed direct synthesis of symmetric biaryl compounds from aryl halides in the presence of tBuLi is described. In situ lithium-halogen exchange generates the corresponding aryl lithium reagent, which undergoes a homocoupling reaction with a second molecule of the aryl halide in the presence of the palladium catalyst (1 mol %). The reaction takes place at room temperature, is fast (1 h), and affords the corresponding biaryl compounds in good to excellent yields. The application of the method is demonstrated in an efficient asymmetric total synthesis of mastigophorene A. The chiral biaryl axis is constructed with an atropselectivity of 9:1 owing to catalyst-induced remote point-to-axial chirality transfer. [ABSTRACT FROM AUTHOR]

The article highlights the chemical equations involved in consecutive dynamic resolutions of phosphine oxides.

An unprecedented catalytic pathway for oxa-Michael addition reactions of alcohols to unsaturated nitriles has been revealed using a PNN pincer ruthenium catalyst with a dearomatized pyridine backbone. The isolation of a catalytically competent Ru-dieneamido complex from the reaction between the Ru catalyst and pentenenitrile in combination with DFT calculations supports a mechanism in which activation of the nitrile through metal-ligand cooperativity is a key step. The nitrile-derived Ru-N moiety is sufficiently Brønsted basic to activate the alcohol and initiate conjugate addition of the alkoxide to the α,β-unsaturated fragment. This reaction proceeds in a concerted manner and involves a six-membered transition state. These features allow the reaction to proceed at ambient temperature in the absence of external base. [ABSTRACT FROM AUTHOR]

An unprecedented catalytic pathway for oxa-Michael addition reactions of alcohols to unsaturated nitriles has been revealed using a PNN pincer ruthenium catalyst with a dearomatized pyridine backbone. The isolation of a catalytically competent Ru-dieneamido complex from the reaction between the Ru catalyst and pentenenitrile in combination with DFT calculations supports a mechanism in which activation of the nitrile through metal-ligand cooperativity is a key step. The nitrile-derived Ru-N moiety is sufficiently Brønsted basic to activate the alcohol and initiate conjugate addition of the alkoxide to the α,β-unsaturated fragment. This reaction proceeds in a concerted manner and involves a six-membered transition state. These features allow the reaction to proceed at ambient temperature in the absence of external base. [ABSTRACT FROM AUTHOR]

New methodology for making novel materials is highly desirable. Here, an 'ingredients' approach to functional self-assembled hydrogels was developed. By designing a building block to contain the right ingredients, a multi-responsive, self-assembled hydrogel was obtained through a process of template-induced self-synthesis in a dynamic combinatorial library. The system can be switched between gel and solution by light, redox reactions, pH, temperature, mechanical energy and sequestration or addition of MgII salt. [ABSTRACT FROM AUTHOR]

The synthesis of bis(formazanate) zinc complexes is described. These complexes have well-behaved redox-chemistry, with the ligands functioning as a reversible electron reservoir. This allows the synthesis of bis(formazanate) zinc compounds in three redox states in which the formazanate ligands are reduced to 'metallaverdazyl' radicals. The stability of these ligand-based radicals is a result of the delocalization of the unpaired electron over four nitrogen atoms in the ligand backbone. The neutral, anionic, and dianionic compounds (L2Zn0/−1/−2) were fully characterized by single-crystal X-ray crystallography, spectroscopic methods, and DFT calculations. In these complexes, the structural features of the formazanate ligands are very similar to well-known β-diketiminates, but the nitrogen-rich (NNCNN) backbone of formazanates opens the door to redox-chemistry that is otherwise not easily accessible. [ABSTRACT FROM AUTHOR]

The synthesis of bis(formazanate) zinc complexes is described. These complexes have well-behaved redox-chemistry, with the ligands functioning as a reversible electron reservoir. This allows the synthesis of bis(formazanate) zinc compounds in three redox states in which the formazanate ligands are reduced to 'metallaverdazyl' radicals. The stability of these ligand-based radicals is a result of the delocalization of the unpaired electron over four nitrogen atoms in the ligand backbone. The neutral, anionic, and dianionic compounds (L2Zn0/−1/−2) were fully characterized by single-crystal X-ray crystallography, spectroscopic methods, and DFT calculations. In these complexes, the structural features of the formazanate ligands are very similar to well-known β-diketiminates, but the nitrogen-rich (NNCNN) backbone of formazanates opens the door to redox-chemistry that is otherwise not easily accessible. [ABSTRACT FROM AUTHOR]

The synthetic value of this aryl-coupling protocol is demonstrated by preparation of mastigophorene A (VII). [ABSTRACT FROM AUTHOR]

The article presents chemical equations for the article "A Metal-Ligand Cooperative Pathway for Intermolecular Oxa-Michael Additions to Unsaturated Nitriles" by S. Perdriau and others, published in a 2015 issue of the periodical "Angewandte Chemie International Edition."

The products are obtained in high yields and excellent enantioselectivity. [ABSTRACT FROM AUTHOR]

Formazans have been known since about 1900 for their intense color, and they find applications as dyestuffs and analytical reagents. In their Communication on page 4118 ff., E. Otten et al. describe formazanate anions as unique ligands in coordination chemistry. The facile and reversible redox chemistry accessible for these ligands allows the full characterization of bis(formazanate) zinc complexes in three oxidation states. Cover image courtesy of Hsin‐Wei Lin. [ABSTRACT FROM AUTHOR]

Formazane werden seit 1900 wegen ihrer intensiven Farbe als Farbstoffe und analytische Reagentien verwendet. In ihrer Zuschrift auf S. 4202 ff. nutzen E. Otten et al. Formazanat ‐ Anionen als redoxaktive Liganden in der Koordinationschemie, und sie charakterisieren Bis(formazanat) ‐ Zinkkomplexe in drei Oxidationszuständen. (Bild: Hsin ‐ Wei Lin) [ABSTRACT FROM AUTHOR]