Gold(I) complexes containing the cationic ylide ligand bis(methyldiphenylphosphonio)methylide

Isolation of a Cyclic Trinuclear Gold(I) Complex with Metalated Phosphorus Ylides: Synthesis and Structural Properties

The first chiral and luminescent cyclic trinuclear gold(I) complex, [{AuCH(PPh2Me)(Ph2P)}3]3+, has been isolated with metalated phosphorus ylides (PY). This complex was initially obtained through the reaction of either mononuclear [C6F5SAuCH(PPh2Me)(Ph2P)]OTf or dinuclear [C6F5S{AuCH(PPh2Me)(Ph2P)}2](OTf)2 thiolate-gold-phosphane complexes in the presence of NaH, followed by the abstraction of the thiopyridine moiety employing either AgOTf or [Cu(CH3CN)4]PF6. Our quest for a more efficient synthesis route led to the development of a streamlined one-pot synthesis method, employing Ag(acac) as both a halogen abstractor and a base, offering a quicker and more direct path to this intriguing trimer. Comprehensive computational studies have unveiled the luminescent characteristics of this complex, which can be attributed to phosphorescence. These emissions originate from ligand-to-metal (LMCT) and metal-centered (MC) charge transfer excited states. Furthermore, the structural analysis via X-ray crystallography corroborated the formation of a trimeric species, featuring three monomers with the [AuCH(PPh2Me)(Ph2P)] motif. Each monomer exhibits a single chiral center, leading to four possible absolute configurations (RRR, RRS, RSR, and SRR). NMR and X-ray spectroscopy have provided valuable insights, establishing that the former configuration (RRR) is disfavored due to steric hindrance, while the three remaining configurations can interconvert, arising from the structural arrangement of the metallacycle and inherent symmetry operations.

Binuclear Macrocyclic Silver(I) Complex of a Bis(carbone) Pincer Ligand: Synthesis and Application as a Carbone-Transfer Agent

A facile synthesis of a binuclear AgI complex 2 of a bis(carbone) ligand L and its application as a carbone-transfer agent for the generation of other transition-metal complexes of AuI (3), NiII (4), and PdII (5) is presented. Complex 2 was synthesized through multiple synthetic routes under mild reaction conditions using the tetracationic [LH4][OTf·Cl]2 precursor salt, the dicationic [LH2][OTf]2 ylide salt, and the free ligand L. The first two synthesis routes require no prior isolation of the air-, moisture-, and temperature-sensitive free ligand L, thus affording complex 2 with high yield and purity. Multinuclear NMR techniques, high-resolution mass spectrometry, and single-crystal X-ray diffraction analysis confirmed the identity of complex 2 as a binuclear AgI complex of L with a molecular formula of [L2Ag2][OTf]2 and a 16-membered-ring metallomacrocyclic structure. During the transmetalation reaction with AuI, the binuclear nature of complex 2 remains intact to give analogous complex 3 ([L2Au2][OTf]2). However, the dimeric structure was disrupted upon the carbone-transfer reaction with NiII and PdII, yielding mononuclear C-N-C pincer-type complexes 4 ([LNiCl][OTf]) and 5 ([LPdCl][OTf]), respectively. These results demonstrated the versatile use of complex 2 as a carbone-transfer agent to other transition metals regardless of the type or size of the metals or the geometry they prefer.

Carbones and Carbon Atom as Ligands in Transition Metal Complexes

This review summarizes experimental and theoretical studies of transition metal complexes with two types of novel metal-carbon bonds. One type features complexes with carbones CL₂ as ligands, where the carbon(0) atom has two electron lone pairs which engage in double (σ and π) donation to the metal atom [M]⇇CL₂. The second part of this review reports complexes which have a neutral carbon atom C as ligand. Carbido complexes with naked carbon atoms may be considered as endpoint of the series [M]-CR₃ → [M]-CR₂ → [M]-CR → [M]-C. This review includes some work on uranium and cerium complexes, but it does not present a complete coverage of actinide and lanthanide complexes with carbone or carbide ligands.

Carbodiphosphorane-based nickel pincer complexes and their (de)protonated analogues: dimerisation, ligand tautomers and proton affinities

The reactivity patterns of carbodiphosphoranes (CDPs) as ligands are much less explored than those of isoelectronic analogues. In the current manuscript, we investigate the reactivity of the carbodiphosphorane-based PCP nickel(ii) pincer complex [({dppm}2C)NiCl]Cl (1) towards acids and bases, calculate proton affinities, analyse the bonding situation and tautomeric forms with the aim to evaluate whether CDPs can potentially act as cooperative ligands in catalysis (dppm = 1,1-bis(diphenylphosphino)methane). Our investigations show that different tautomeric forms are stable for the coordinated and the uncoordinated ligand. The protonated CDP-based complex 2 represents a rare example of a cationic donor group binding to a cationic metal centre. The continuous arm-deprotonation of 1 leads to the formation of remarkably stable dimers with Ni-C-P-C-metallacycles. In comparison to corresponding boron and amine-based ligands, the coordinated CDP-group exhibits the lowest proton affinity according to DFT calculations, indicating that coordinated CDP ligands can potentially serve as proton relay in cooperative catalysis.

N-Heterocyclic carbene or phosphorus ylide: which one forms a stronger bond with group 11 metals? A theoretical study

N-Heterocyclic carbene and phosphorus ylides are inorganic and organometallic ligands, and their coordination chemistry with transition elements, particularly group 11 metals, would be noticeable. This study seeks to characterize the structure and nature of the C→M bond of group 11 metals (M = Cu(i), Ag(i), Au(i)) in coordination with different monodentate phosphorus ylides {P(Ph)₃CHR} and N-heterocyclic carbenes (NHC(R)) (where R = F, Cl, Br, CF₃, CH₃, H, C(CH₃)₃, Si(CH₃)₃, SiH₃, Ph). In this regard, DFT calculations with the PBE/def2-TZVP level of theory were applied. The results show that the M←C bond interaction energies (ΔE_int) related to [NHC(R) → MR'] and [{P(Ph)₃CHR} → MCl] complexes (M = Cu(i), Ag(i), Au(i); R = F, Cl, Br, CF₃, H, CH₃, C(CH₃)₃, Si(CH₃)₃, SiH₃, Ph; R' = Cl, OAc) are substantial and conform to the well-known V-shaped trend for the transition metals of the first, second, and third row in the following order: Ag(i) < Cu(i) < Au(i). The nature of the C→M bond in the complexes was analyzed using NBO, AIM, EDA, and ETS-NOCV. The nature of the C→M bond interactions in [NHC(R) → MR'] and [{P(Ph)₃CHR} → MCl] complexes studied here is largely electrostatic, and this feature accounts for about 65%-74% of the total interaction energy. Furthermore, it is found that in the presence of electron-donating substituents, the group 11 metals form stronger bonds with NHC(R) rather than monodentate phosphorus ylides. Comparison of the EDA-NOCV results for the M←C bond with the same M atom and R substituent in [NHC(R) → MR'] and [{P(Ph)₃CHR} → MCl] indicates that the monodentate phosphorus ylide ligands studied here ({P(Ph)₃CHR}) are slightly better σ-donors and weaker π-acceptors than the corresponding NHC(R) ligands.

Coordination chemistry at carbon: the patchwork family comprising (Ph3P)2C, (Ph3P)C(C2H4), and (C2H4)2C

The revitalized concept of "coordination at carbon" allows relationships between seemingly unrelated families of carbon-centered compounds to be discovered generating fascinating patchwork families of compounds. It is shown how olefins and cyclopropanes can be regarded as donors for carbon acceptors C(1), C(2), and C(3). Through this approach, hydrocarbons such as spiropentane and dicyclopropylidene are found to be counterparts of the bis-ylidic carbodiphosphoranes and the corresponding mixed mono-ylidic systems.

Stable singlet carbenes as mimics for transition metal centers

This perspective summarizes recent results, which demonstrate that stable carbenes can activate small molecules (CO, H(2), NH(3) and P(4)) and stabilize highly reactive intermediates (main group elements in the zero oxidation state and paramagnetic species). These two tasks were previously exclusive for transition metal complexes.

Stable cyclic carbenes and related species beyond diaminocarbenes

The success of homogeneous catalysis can be attributed largely to the development of a diverse range of ligand frameworks that have been used to tune the behavior of various systems. Spectacular results in this area have been achieved using cyclic diaminocarbenes (NHCs) as a result of their strong σ-donor properties. Although it is possible to cursorily tune the structure of NHCs, any diversity is still far from matching their phosphorus-based counterparts, which is one of the great strengths of the latter. A variety of stable acyclic carbenes are known, but they are either reluctant to bind metals or they give rise to fragile metal complexes. During the last five years, new types of stable cyclic carbenes, as well as related carbon-based ligands (which are not NHCs), and which feature even stronger σ-donor properties have been developed. Their synthesis and characterization as well as the stability, electronic properties, coordination behavior, and catalytic activity of the ensuing complexes are discussed, and comparisons with their NHC cousins are made.

Novel route to carbodiphosphoranes producing a new P,C,P pincer carbene ligand

The reaction of PdCl2, dppm and CS2 in CH(2)Cl(2)/MeOH results in the palladium carbodiphosphorane complex [Pd(Ph(2)PCH(2)Ph(2)PCPPh(2)CH(2)PPh(2)-P,C,P)Cl]Cl.