Controlling the reactivity of transition metals using secondary, s-accepting ligands is an active area of investigation that is impacting molecular catalysis.H erein we describe the phosphine gold complexes [(o-Ph 2 P(C 6 H 4 )Acr)AuCl] + ([3] + ;A cr = 9-N-methylacridinium) and [(o-Ph 2 P-(C 6 H 4 )Xan)AuCl] + ([4] + ;X an = 9-xanthylium) where the electrophilic carbenium moiety is juxtaposed with the metal atom. While only weak interactions occur between the gold atom and the carbenium moiety of these complexes,t he more Lewis acidic complex [4] + readily reacts with chloride to afford at rivalent phosphine gold dichloride derivative (7)i nw hich the metal atom is covalently bound to the former carbocationic center.This anion-induced Au I /Au III oxidation is accompanied by aconversion of the Lewis acidic carbocationic center in [4] + into an X-type ligand in 7.W ec onclude that the carbenium moiety of this complex acts as alatent Z-type ligand poised to increase the Lewis acidity of the gold center,anotion supported by the carbophilic reactivity of these complexes.

The reactivity of the reduced Zr/Co and Ti/Co complexes (THF)­Zr­(MesNP i Pr2)3CoN2 (1, Mes = 2,4,6-trimethylphenyl) and (THF)­Ti­(XylNP i Pr2)3CoN2 (7, Xyl = 3,5-dimethylphenyl) toward diaryl ketones is explored in an effort to gain mechanistic insight into CO bond cleavage processes. Complex 1 reacts with 4,4′-dimethoxybenzophenone to generate ((p-OMeC6H4)2CO)­Zr­(MesNP i Pr2)3CoN2 (2), which exists as a mixture of valence tautomers in solution that interconvert via electron transfer from Co–I to the Zr-bound ketone in 2 S to form a Zr-bound ketyl radical in 2 T . The geometry of 2 in the solid state is most consistent with the singlet ketone adduct tautomer 2 S . Upon removal of the Co-bound N2 under vacuum, complex 2 cleanly coverts to the μ-oxo carbene product (η2-MesNP i Pr2)­Zr­(MesNP i Pr2)2(μ-O)­CoC­(C6H4 p-OMe)2 (5) at room temperature in solution. A diamagnetic intermediate, tentatively assigned as ketone-bridged species (η2-MesNP i Pr2)­Zr­(MesNP i Pr2)2Co­(μ2,η1η2-OC­(p-OMeC6H4)2) (6), is observed spectroscopically during the transformation of 1 to 5. Similar reactions between the Ti/Co analogue 7 and diaryl ketones reveal no evidence for electron-transfer to form triplet ketyl radical species. Complex 7 reacts with 4,4′-dimethoxybenzophenone to afford diamagnetic ((p-OMeC6H4)2CO)­Ti­(XylNP i Pr2)3CoN2 (8). In contrast, addition of benzophenone to 7 under N2 generates a mixture of (η2-XylNP i Pr2)­Ti­(XylNP i Pr2)2Co­(η2-OCPh2) (9) and (Ph2CO)­Ti­(XylNP i Pr2)3CoN2 (10) in solution, and C 3-symmetric 10 is found to be favored in the solid state. Complex 9 can be generated exclusively and isolated in the absence of N2. Ti/Co complexes 8–10 are thermally stable and do not undergo CO bond cleavage even at elevated temperature, in stark contrast to their Zr/Co congeners.

This work describes the synthesis of carbenium-based, γ-cationic phosphines and their coordination to Au(i) cations , leading to carbophilic catalysts whose activity is enhanced by the ligand-enforced convergence of the positively charged moieties.

Aiming to study the interaction of gold with the highly Lewis acidic fluorenyl cation, we synthesized (o-[Ph2P(C6H4)Flu)AuCl(tht)][BF4] ([2][BF4]) and (o-Ph2P(C6H4)Flu)AuCl2 (3) (Flu = 9-fluorenyl) and found that the latter could...

As part of our efforts to interface late transition metals with Lewis acidic main group fragments, we have decided to investigate gold complexes bearing halogermanes as Z‐type ligands. Toward this end, we have synthesized complexes of general formula [(o‐(Ph2P)C6H4)2(Ph)(X)GeAuCl] (X = F, Cl). Experimental and computational analyses indicate the presence of an Au→Ge interaction in both cases. Chloride abstraction reactions have also been investigated. In the case of X = Cl, double chloride abstraction with AgSbF6 affords a putative dication that gradually abstracts fluoride from its counterion. This putative dication is also significantly more active as a catalyst than its monocationic analog in alkyne hydroamination reactions.