Ligand Exchange and Molecular Aggregation of an Ag-Sn Heterobimetallic Complex: First Structural Characterization of an Ag-Sn Bond

Impact of High Pressure on Metallophilic Interactions and Its Consequences for Spectroscopic Properties of a Model Tetranuclear Silver(I)-Copper(I) Complex in the Solid State

Structure-property relationships were investigated via combined high-pressure spectroscopic and X-ray diffraction techniques for a model luminescent Ag₂Cu₂L₄ (L = 2-diphenylphosphino-3-methylindole) complex in the crystalline state. The experimental results were contributed by theoretical calculations, compared with the previously evaluated light-induced geometrical changes, and discussed in the context of available literature to date. To the best of our knowledge, this is the first study of this kind devoted to a coinage-metal complex for which the argentophilic interactions are crucial. High-pressure X-ray diffraction and optical spectroscopy experiments showed close correspondence between structural changes and optical properties. The unit-cell angles, absorption edges, emission maxima, decay lifetimes and silver-copper bond trends, all change around 2-3 GPa. A blue-shift to red-shift switch when increasing the pressure was observed for both absorption and emission spectra. This is unique behavior when compared to the literature-reported coinage metal systems. It also occurred that the pressure-induced structural changes differ notably from the geometrical distortions observed for the excited state. Interestingly, shortening of the Ag-Ag bond itself does not ensure the red shift of the absorption and emission spectra. All the optical spectroscopy data are suggestive of an important role of defects, likely related to the lack of a hydrostatic pressure transmitting medium, for pressures higher than 3 GPa.

Strikingly diverse reactivity of structurally identical silylene and stannylene

The divergent reactivity of structurally similar silylene and stannylene was observed with coinage metal halides. While the former tends to form an adduct, the latter undergoes ligand exchange reaction.

Coordination Chemistry of Cyclic Disilylated Germylenes and Stannylenes with Group 11 Metals

Reactions of Et₃P adducts of bissilylated germylenes and stannylenes with gold, silver, and copper cyanides led to cyanogermyl or -stannyl complexes of the respective metals. In the course of the reaction the phosphine moved to the metal, while the cyanide migrated to the low-coordinate group 14 element. The respective gold complexes were found to be monomeric, whereas the silver and copper complexes exhibited a tendency to dimerize in the solid state. Attempts to abstract the phosphine ligand with B(C₆F₅)₃ led only to the formation of adducts with the borane coordinating to the cyanide nitrogen atom.

Shedding light on the photochemistry of coinage-metal phosphorescent materials: a time-resolved Laue diffraction study of an Ag(I)-Cu(I) tetranuclear complex

The triplet excited state of a new crystalline form of a tetranuclear coordination d(10)-d(10)-type complex, Ag2Cu2L4 (L = 2-diphenylphosphino-3-methylindole ligand), containing Ag(I) and Cu(I) metal centers has been explored using the Laue pump-probe technique with ≈80 ps time resolution. The relatively short lifetime of 1 μs is accompanied by significant photoinduced structural changes, as large as the Ag1···Cu2 distance shortening by 0.59(3) Å. The results show a pronounced strengthening of the argentophilic interactions and formation of new Ag···Cu bonds on excitation. Theoretical calculations indicate that the structural changes are due to a ligand-to-metal charge transfer (LMCT) strengthening the Ag···Ag interaction, mainly occurring from the methylindole ligands to the silver metal centers. QM/MM optimizations of the ground and excited states of the complex support the experimental results. Comparison with isolated molecule optimizations demonstrates the restricting effect of the crystalline matrix on photoinduced distortions. The work represents the first time-resolved Laue diffraction study of a heteronuclear coordination complex and provides new information on the nature of photoresponse of coinage metal complexes, which have been the subject of extensive studies.

Silver Aggregation Caused by Stanna-closo-dodecaborate Coordination: Syntheses, Solid-State Structures and Theoretical Studies

Stanna-closo-dodecaborate [SnB11H11]2- reacts as a nucleophile with various silver electrophiles ([Ag(PMe3)]+, [Ag(PEt3)]+, [Ag(PPh3)]+, and Ag+) to form silver-tin bonds. Aggregation of two, three, or four units of [{Ag(SnB11H11)(PR3)}n]n- (PPh3, n = 2; PEt3, n = 3; PMe3, n = 4) was found, depending on the size of the coordinating phosphine. The structures of the silver-tin clusters in the solid state were determined by single-crystal X-ray diffraction. In these phosphine silver coordination compounds, the tin ligand exhibits micro2- and micro3-coordination with the silver atoms. From the reaction with silver nitrate, an octaanionic stanna-closo-dodecaborate coordination compound, [Et4N]8[Ag4(SnB11H11)6], was isolated. In this cluster, arranged as butterfly, the stannaborate shows various coordination modes at four silver atoms. In the reported silver-tin complexes, the silver-silver interatomic distances are in a range of 2.6326(10)-3.1424(6) A. Silver-tin distances were found between 2.6416(5) and 3.1460(6) A. Analysis of the molecular orbitals calculated by means of density functional theory shows that the LUMO of the core compound without [SnB11H11]2- units is always a totally symmetric combination of (mainly) s-orbitals of Ag atoms. This core is filled with electrons of the HOMOs of the [SnB11H11]2- units and is leading, in this way, to a stable compound.

Syntheses and structural characterization of the heavier alkali-metal stannates bearing the tripodal triamino framework: structural trends in the series of [MeSi(SiMe2N(4-CH3C6H4))3Sn][M] (M = Na, K, Rb)

Treatment of the lithium stannate [MeSi(SiMe(2)N(4-CH(3)C(6)H(4)))(3)SnLi(OEt(2))] (1) with AgCl yielded the corresponding distannane [MeSi(SiMe(2)N(4-CH(3)C(6)H(4)))(3)Sn](2) (2) as the product of an oxidative coupling in good yield. The distannane (2) underwent reductive cleavage with the heavier alkali metals (sodium, potassium, rubidium) in a non-coordinating solvent (toluene or cyclohexane), to afford the solvate-free stannates(II) [MeSi(SiMe(2)N(4-CH(3)C(6)H(4)))(3)Sn][M] (M = Na (3), K (4), and Rb (5)), which were structurally characterized. The Na atom in 3 is directly bonded to two of the three amido-N atoms of the stannate cage and additionally solvated by pi-coordination of a tolyl substituent of a neighboring stannate cage. In contrast, the group 1 metal cations in the two isomorphous compounds 4 and 5 are further removed from the nitrogen functions and are pi-coordinated by three tolyl arene rings. The Sn-K distances in 4 were found to be 3.635 and 3.870 A, whereas the Sn-Rb contacts in 5 are 3.708 and 3.908 A; these are the first such Sn-Rb bonding contacts to be characterized in a molecular compound by X-ray diffraction.

Tris(amido)tingold Complexes in Different Oxidation States. First Structural Characterization of a Sn-Au-Au-Sn Linear Chain

The reaction of [MeSi{Me(2)SiN(Li)(p-tol)}(3)(Et(2)O)(2)] with SnCl(2) in a 1:1 molar ratio leads the tris(amido)stannate [MeSi{Me(2)SiN(p-tol)}(3)SnLi(Et(2)O)] (1), which further reacts with neutral [AuCl(PPh(3))] and anionic [PPN][AuCl(2)], PPN[AuRCl] (R = C(6)F(5), mes), and chlorogold(I) complexes yielding [Au(MeSi{Me(2)SiN(p-tol)}(3)Sn)(PPh(3))] (2) and [PPN][Au(MeSi{Me(2)SiN(p-tol)}(3)Sn)(2)] (3) and [Au(MeSi{Me(2)SiN(p-tol)}(3)Sn)(R)] (R = C(6)F(5), 4; R = mes, 5), respectively. The reaction of 1 with the dinuclear gold(II) derivative [Au(2)(CH(2)PPh(2)CH(2))(2)Cl(2)] in a 1:2 ratio affords [Au(2)(CH(2)PPh(2)CH(2))(2)(MeSi{Me(2)SiN(p-tol)}(3)Sn)(2)] (6). In a similar way but starting from PPN[Au(C(6)F(5))(3)Cl] and reacting with 1 in a 1:1 ratio, the Au(III) complex [PPN][Au(MeSi{Me(2)SiN(p-tol)}(3)Sn)(C(6)F(5))(3)] (7) has been obtained. X-ray crystal structure analyses were performed for compounds 2 and 6, establishing the Sn-Au bonds [d(Au-Sn) = 2.5651(13) and 2.6804(13) Å, respectively). Compound 6 has a nearly linear Sn-Au-Au-Sn array and features the first examples of tin-gold(II) bonds.