C(sp)-H, S-H, and Sn-H Bond Activation with a Cobalt(I) Pincer Complex.

This study focuses on the stoichiometric reactions of {2,6-(iPr2PO)2C6H3}Co(PMe3)2 with terminal alkynes, thiols, and tin hydrides as part of an effort to develop catalytic, two-electron processes with cobalt. This specific Co(I) pincer complex proves to be effective for cleaving the C(sp)-H, S-H, and Sn-H bonds to give oxidative addition products with the general formula {2,6-(iPr2PO)2C6H3}CoHX(PMe3) (X = alkynyl, thiolate, and stannyl groups) along with the free PMe3. These reactions typically reach completion when the substituents on acetylene, sulfur, and tin are electron-withdrawing groups (e.g., phenyl, pyridyl, and alkenyl groups). In contrast, alkyl-substituted acetylenes, 1-pentanethiol, and tributyltin hydride are partially converted due to the equilibria with the corresponding oxidative addition products. The Co(I) pincer complex is not a hydrothiolation catalyst but capable of catalyzing the hydrostannation of terminal alkynes with Ph3SnH to produce ß-(Z)-alkenylstannanes selectively.

Remodeling of N-Heterocyclic Iminato Ligand Frameworks for the Facile Synthesis of Isoureas from Alcohols and Carbodiimides Promoted by Organoactinide (Th, U) Complexes.

A new class of actinide complexes [(L)An(N{SiMe3}2)3] (An = Th or U) (Th1-Th3 and U1-U3) supported by highly nucleophilic seven-membered N-heterocyclic iminato ligands were synthesized and fully characterized by single-crystal X-ray diffraction. These complexes were successfully exploited as powerful catalysts for the addition of alcohols to carbodiimides to yield the corresponding desirable isourea products at room temperature with short reaction times and excellent yields. Thorough stoichiometric, thermodynamic, and kinetic studies were carried out, allowing us to propose a plausible mechanism for the catalytic reaction.

Recent developments in highly basic N-heterocyclic iminato ligands in actinide chemistry.

In the last decade, major conceptual advances in the chemistry of actinide molecules and materials have been made to demonstrate their distinct reactivity profiles as compared to lanthanide and transition metal compounds, but some difficult questions remain concerning the intriguing stability of low-valent actinide complexes, and the importance of the 5f-orbitals in reactivity and bonding. The imidazolin-2-iminato moiety has been extensively used in ligands for the advancement of actinide chemistry owing to its unique capability of stabilizing the reactive and highly electrophilic metal ions by virtue of its strong electron donation and steric tunability. The current review article describes recent developments in the chemistry of light actinide metal ions (thorium and uranium) bearing these N-heterocyclic iminato moieties as supporting ligands. In addition, the effect of ring expansion of the N-heterocycle on the catalytic aptitude of the organoactinides is also described herein. The synthesis and reactivity of actinide complexes bearing N-heterocyclic iminato ligands are presented, and promising apposite applications are also presented. The current review focuses on addressing the catalytic behavior of actinide complexes with oxygen-containing substrates such as in the Tishchenko reaction, hydroelementation processes, and polymerization reactions. Actinide complexes have also found new catalytic applications, as demonstrated by the potent chemoselective carbonyl hydroboration and tandem proton-transfer esterification (TPTE) reaction, featuring coupling between an aldehyde and alcohol.

Mild catalytic deoxygenation of amides promoted by thorium metallocene.

The organoactinide-catalyzed (Cp*2ThMe2) hydroborated reduction of a wide range of tertiary, secondary, and primary amides to the corresponding amines/amine-borane adducts via deoxygenation of the amides is reported herein. The catalytic reactions proceed under mild conditions with low catalyst loading and pinacolborane (HBpin) concentration in a selective fashion. Cp*2ThMe2 is capable of efficiently catalysing the gram-scale reaction without a drop in efficiency. The amine-borane adducts are successfully converted into free amine products in high conversions, which increases the usefulness of this catalytic system. A plausible mechanism is proposed based on detailed kinetics, stoichiometric, and deuterium labeling studies.

Inter-ligand electronic coupling mediated through a dimetal bridge: dependence on metal ions and ancillary ligands.

A series of Mo2, Ru2, Rh2 and Cu2 complexes with redox-active NP-R [2-(2-R)-1,8-naphthyridine; R = pyrazinyl (NP-pz, L1) and thiazolyl (NP-tz, L2)] ligands have been synthesized and characterized by X-ray crystallography and spectroscopic methods. Two NP-R ligands wrap the dimetal core by occupying four equatorial positions and two axial sites. The remaining four equatorial sites are engaged by bridging acetates in quadruply bonded cis-[Mo2(L1)2(OAc)2][BF4]2 (1), cis-[Mo2(L2)2(OAc)2][BF4]2 (1A), doubly bonded cis-[Ru2(L1)2(OAc)2][ClO4]2 (3), cis-[Ru2(L2)2(OAc)2][ClO4]2 (3A) and singly bonded trans-[Rh2(L1)2(OAc)2][BF4]2 (5) and trans-[Rh2(L2)2(OAc)2][BF4]2 (5A). Compounds cis-[Mo2(L1)2(CH3CN)4][BF4]4 (2), cis-[Mo2(L2)2(CH3CN)4][BF4]4 (2A), cis-[Ru2(L1)2(CO)4][OTf]2 (4) and cis-[Ru2(L2)2(CO)4][ClO4]2 (4A) contain acetonitriles or carbonyls as the ancillary ligands. The dicopper complexes trans-[Cu2(CH3CN)(L1)2][ClO4]2 (6) and trans-[Cu2(L2)2(ClO4)2] (6A) involve no bonding interaction between two Cu(i) units. Cyclic voltammogram studies reveal that two one-electron processes corresponding to each of the two ligands bound to the metal-metal bonded dimetal core result in four reversible one-electron reductions, with the exception of dirhodium(ii,ii) compounds 5 and 5A which show two one-electron reductions. The highest comproportionation constant (Kc) values are obtained for inter-valence complexes originating from the diruthenium(ii,ii) compounds 3 and 3A, whereas no electron delocalization is observed for dicopper(i,i) complexes 6 and 6A. The dimetal bridge and the ancillary ligands tune the degree of inter-ligand electronic coupling in these complexes. DFT calculations reveal a π*(NP)-δ*(M2)-π*(NP) orbital conduit for electron delocalization. For diruthenium(ii,ii) compounds 3 and 3A, an additional π*(NP)-π*(M2)-π*(NP) pathway is accessible contributing to high Kc values. The ancillary π-ligands (acetates and carbonyls) reduce the extent of the electron flow through π*(NP)-δ*(M2)-π*(NP) and thus lower the Kc values. The absence of metal-metal bond orbitals and the reduced metal-ligand covalency in dicopper(i,i) compounds are responsible for the lack of electron delocalization in these systems.