Gauging the donor strength of iron(0) complexes their N-heterocyclic carbene gold(I) adducts.

We isolate and characterize the gold(I)-iron(0) adducts [(Pr-bimy)Au-Fe(CO)(PMe)][BAr] and [Au-{Fe(CO)(PMe)}][BAr] (Pr-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene, BAr = tetrakis(pentafluorophenyl)borate). DFT analysis reveals that the gold-iron interaction in [(Pr-bimy)Au-Fe(CO)(PMe)][BAr] is predominantly a σ-donation from iron to gold. We further extend this class of compounds to include [(Pr-bimy)Au-Fe(CO)(PR)][BAr] (PR = PPh, PCy, PCyPh, PMePh, PMePh, P(4-CHF)) and [(Pr-bimy)Au-Fe(CO)(PPh)][BAr] and correlate the Pr-bimy carbenic C NMR signal with the relative donor strength of the iron(0) ligand.

Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C-X Bonds.

We report the formation and full characterization of weak adducts between Li and Na cations and a neutral iron(0) complex, [Fe(CO)(PMe)] (), supported by weakly coordinating [BAr] anions, [·M][BAr] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)(PMe)][BAr], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and cross-coupling reactions and the formation of new C-E bonds (E = C, H, O, N, S).

Access to and Reactivity of Fe , Fe , Fe , and Fe PC P Pincer Complexes.

Despite their promising metal-ligand cooperative reactivity, PC P pincer ligands are rarely reported for first-row transition-metal centres. Using a dehydration methodology, we report access to an Fe PC P pincer complex (1) that proceeds via an isolated α-hydroxylalkyl hydrido complex (3). Reversible carbonyl migration to the carbene position in 1 is found to allow coordination chemistry and E-H bond addition (E=H, B, Cl) across the iron-carbene linkage, representing a unique mechanism for metal-ligand cooperativity.

Zero valent iron complexes as base partners in frustrated Lewis pair chemistry.

The prototypical iron(0) complex [Fe(CO)3(PMe3)2] (1) forms a frustrated Lewis pair (FLP) with B(C6F5)3 (BCF). In this FLP, the iron complex acts as the Lewis base partner, and the borane as the Lewis acid partner. This FLP is able to cleave H-H, H-Cl, H-O and H-S bonds in H2, HCl, H2O and HSPh.

C-N, C-S and S-S Bond Cleavage by Rhodium PC P Pincer Complexes.

Rhodium PC P complexes 1-L {L=PPh , PPh (C F )} react with isothiocyanate, carbodiimide and disulphide to enable C-S, C-N and S-S bond cleavage. The cleaved molecules are sequestered by the metal center and the pincer alkylidene linkage, forming η -coordinated sulfide or imide centered pincer complexes. When a C-S or S-S bond is cleaved, the resulting complexes can bridge two rhodium centers through sulphur forming dimeric complexes and eliminating a monodentate phosphine ligand.

Direct oxide transfer from an η-keto ligand to generate a cobalt PCP(O) pincer complex.

We report the direct carbonyl cleavage in a κ-P',(η-C,O),P'' ligand by a monomeric cobalt centre through metal-ligand cooperativity. C-O cleavage leads to the formation of a PCP(O) pincer ligand with a central alkylidene anchor. A DFT analysis, supported by kinetic studies, suggests that decoordination of a pincer phosphino arm to generate a kinetically accessible free phosphine may be critical in transfer of the oxide to a phosphorus position.

Synthesis and reactivity of α-cationic phosphines: the effect of imidazolinium and amidinium substituents.

Mono- and dicationic phosphines have been synthesized through the reaction of chloroimidazolinium or chloroamidinium salts with secondary or primary phosphines respectively. The resulting ligands, which depict a significantly reduced donor ability compared with their neutral analogues, have been used to design Pt(II) and Au(I) complexes that effectively catalyse the hydroarylation of alkynes.

Synthesis, structure, and applications of pyridiniophosphines.

A new family of cationic ligands, N-alkyl/aryl pyridiniophosphines, has been synthesized through a short, scalable, and highly modular route. Evaluation of their electronic properties evidenced weak σ-donor and quite strong π-acceptor character when used as ancillary ligands. These attributes confer a substantially enhanced π-acidity to the Pt(II) and Au(I) complexes thereof derived and, as result, they depict an improved ability to activate alkynes towards nucleophilic attack.