Synthesis of a Cyclic Co₂Sn₂ Cluster Using a Co^– Synthon

[Ar′SnCo]2 ( 1 , Ar′ = C6H3-2,6{C6H3-2,6-iPr2}2), a rare metal–metal bonded cobalt–tin cluster with low-coordinate tin atoms, was prepared by the reaction of [K(thf)0.2][Co(1,5-cod)2] (cod = 1,5-cyclooctadiene) with [Ar′Sn(μ-Cl)]2. This reaction illustrates a promising synthetic strategy to access uncommon metal clusters. The structure of 1 features a rhomboidal Co2Sn2 core with strong metal–metal bonds between tin and cobalt and a weaker tin–tin interaction. Reaction of 1 with white phosphorus afforded [Ar′2Sn2Co2P4] ( 2 ), the first molecular cluster compound containing phosphorus, cobalt and tin

Synthesis of a Cyclic Co2Sn2 Cluster Using a Co- Synthon.

[Ar'SnCo]2 (1, Ar' = C6H3-2,6{C6H3-2,6- iPr2}2), a rare metal-metal bonded cobalt-tin cluster with low-coordinate tin atoms, was prepared by the reaction of [K(thf)0.2][Co(1,5-cod)2] (cod = 1,5-cyclooctadiene) with [Ar'Sn(μ-Cl)]2. This reaction illustrates a promising synthetic strategy to access uncommon metal clusters. The structure of 1 features a rhomboidal Co2Sn2 core with strong metal-metal bonds between tin and cobalt and a weaker tin-tin interaction. Reaction of 1 with white phosphorus afforded [Ar'2Sn2Co2P4] (2), the first molecular cluster compound containing phosphorus, cobalt and tin

Cleavage of Ge–Ge and Sn–Sn Triple Bonds in Heavy Group 14 Element Alkyne Analogues (EAriPr4)2 (E = Ge, Sn; AriPr4 = C6H3-2,6(C6H3-2,6-iPr2)2) by Reaction with Group 6 Carbonyls

The reactions of heavier group 14 element alkyne analogues (EAriPr4)2 (E = Ge, Sn; AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) with the group 6 transition-metal carbonyls M(CO)6 (M = Cr, Mo, W) under UV irradiation resulted in the cleavage of the E–E triple bond and the formation of the complexes {AriPr4EM(CO)4}2 (1–6), which were characterized by single crystal X-ray diffraction as well as by IR and multinuclear NMR spectroscopy. Single-crystal X-ray structural analyses of 1–6 showed that the complexes have a nearly planar rhomboid M2E2 core with three-coordinate group 14 atoms. The coordination geometry at the group 6 metals is distorted octahedral formed by four carbonyl groups as well as two bridging EAriPr4 units. IR spectroscopic data suggest that the EAriPr4 units are not very efficient π-acceptors, but the investigation of E–M metal–metal interactions in 1–6 with computational methods revealed the importance of both σ- and π-type contributions to bonding. The mechanism for the insertion of transition-metal carbonyls into E–E bonds in (EAriPr4)2 was also probed computationally.peerReviewe

Reactions of Terphenyl-Substituted Digallene AriPr4GaGaAriPr4 (AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) with Transition Metal Carbonyls and Theoretical Investigation of the Mechanism of Addition

The neutral digallene AriPr4GaGaAriPr4 (AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) was shown to react at ca. 25 °C in pentane solution with group 6 transition metal carbonyl complexes M(CO)6 (M = Cr, Mo, W) under UV irradiation to afford compounds of the general formula trans-[M(GaAriPr4)2(CO)4] in modest yields. The bis(gallanediyl) complexes were characterized spectroscopically and by X-ray crystallography, which demonstrated that they were isostructural. In each complex, the gallium atom is two-coordinate with essentially linear geometry, which is relatively rare for gallanediyl-substituted transition metal species. The experimental data show that the gallanediyl ligand :GaAriPr4 behaves as a good σ-donor but a poor π-acceptor, in agreement with prior theoretical analyses on related systems. In addition, the monogallanediyl complex Mo(GaAriPr4)(CO)5 was synthesized by reacting AriPr4GaGaAriPr4 with two equivalents of Mo(CO)5NMe3 in THF solution. The mechanism of the reaction between AriPr4GaGaAriPr4 and Cr(CO)6 was probed computationally using density functional theory. The results suggest that the reaction proceeds via an intermediate monogallanediyl complex, Cr(GaAriPr4)(CO)5, that can be generated via two pathways, one of which involves the dimeric AriPr4GaGaAriPr4, that are possibly competing. AriPr4GaGaAriPr4 was also shown to react readily under ambient conditions with Co2(CO)8 to give the monosubstituted dicobalt complex Co2(μ-GaAriPr4)(μ-CO)(CO)6 by X-ray crystallography. The :GaAriPr4 unit bridges the Co–Co bond unsymmetrically in the solid state. No evidence was found for incorporation of more than one :GaAriPr4 unit into the dicobalt complex.peerReviewe

The Reactions of Aryl Tin(II) Hydrides {Ar^<i>i</i>Pr6Sn(μ-H)}₂ (Ar^<i>i</i>Pr6 = C₆H₃‑2,6-(C₆H₂‑2,4,6‑^<i>i</i>Pr₃)₂) and {Ar^<i>i</i>Pr4Sn(μ-H)}₂ (Ar^<i>i</i>Pr4 = C₆H₃‑2,6-(C₆H₃‑2,6‑^<i>i</i>Pr₂)₂) with Aryl Alkynes: Substituent Dependent Structural Isomers

The reactions of the aryl tin­(II) hydrides {Ar^<i>i</i>Pr6Sn­(μ-H)}₂ (Ar^<i>i</i>Pr6 = C₆H₃-2,6-(C₆H₂-2,4,6-^<i>i</i>Pr₃)₂) and {Ar^<i>i</i>Pr4Sn­(μ-H)}₂ (Ar^<i>i</i>Pr4 = C₆H₃-2,6-(C₆H₃-2,6-^<i>i</i>Pr₂)₂) with aryl alkynes were investigated. Reaction of {Ar^<i>i</i>Pr6Sn­(μ-H)}₂ and {Ar^<i>i</i>Pr4Sn­(μ-H)}₂ with 2 equiv of diphenyl acetylene, PhCCPh, afforded the aryl alkenyl stannylenes Ar^<i>i</i>Pr6SnC­(Ph)­C­(H)­Ph (<b>1</b>) and Ar^<i>i</i>Pr4SnC­(Ph)­C­(H)­Ph (<b>2</b>). In contrast, the analogous reactions of {Ar^<i>i</i>Pr6Sn­(μ-H)}₂ with 2 equiv of phenyl acetylene, HCCPh, afforded a high yield of the <i>cis</i>-1,2 addition product Ar^<i>i</i>Pr6(H)SnC­(H)­C­(Ph)Sn­(H)­Ar^<i>i</i>Pr6 (<b>3</b>), which has a four-membered Sn₂C₂ core structure comprised of two Sn–Sn bonded Sn­(H)­Ar^<i>i</i>Pr6 units bridged by a −C­(H)C­(Ph)– moiety. The corresponding reaction of the less bulky hydride {Ar^<i>i</i>Pr4Sn­(μ-H)}₂ with 2 equiv of phenyl acetylene leads to Ar^<i>i</i>Pr4SnC­(H)­C­(Ph)­Sn­(H)₂Ar^<i>i</i>Pr4 (<b>4</b>) which unlike <b>3</b> has no Sn–Sn bonding. Instead, the tin atoms are connected solely by a −C­(H)C­(Ph)– moiety. Each tin atom carries a Ar^<i>i</i>Pr4 substituent but one is also substituted by two hydrogens. The difference in behavior between PhCCPh and HCCPh is attributed mainly to the difference in steric bulk of the two substrates. The different products <b>3</b> and <b>4</b> are probably a consequence of the difference in size and dispersion force interactions of the Ar^<i>i</i>Pr6 and Ar^<i>i</i>Pr4 substituents. Compounds <b>1</b>–<b>4</b> were characterized by ¹H, ¹³C, and ¹¹⁹Sn NMR, UV–vis, and IR spectroscopy and structurally by X-ray crystallography

Reactions of Terphenyl-Substituted Digallene Ar^{<i>i</i>Pr₄}GaGaAr^{<i>i</i>Pr₄} (Ar^{<i>i</i>Pr₄} = C₆H₃‑2,6-(C₆H₃‑2,6‑^<i>i</i>Pr₂)₂) with Transition Metal Carbonyls and Theoretical Investigation of the Mechanism of Addition

The neutral digallene Ar^{<i>i</i>Pr₄}GaGaAr^{<i>i</i>Pr₄} (Ar^{<i>i</i>Pr₄} = C₆H₃-2,6-(C₆H₃-2,6-^<i>i</i>Pr₂)₂) was shown to react at ca. 25 °C in pentane solution with group 6 transition metal carbonyl complexes M­(CO)₆ (M = Cr, Mo, W) under UV irradiation to afford compounds of the general formula <i>trans</i>-[M­(GaAr^{<i>i</i>Pr₄})₂(CO)₄] in modest yields. The bis­(gallanediyl) complexes were characterized spectroscopically and by X-ray crystallography, which demonstrated that they were isostructural. In each complex, the gallium atom is two-coordinate with essentially linear geometry, which is relatively rare for gallanediyl-substituted transition metal species. The experimental data show that the gallanediyl ligand :GaAr^{<i>i</i>Pr₄} behaves as a good σ-donor but a poor π-acceptor, in agreement with prior theoretical analyses on related systems. In addition, the monogallanediyl complex Mo­(GaAr^{<i>i</i>Pr₄})­(CO)₅ was synthesized by reacting Ar^{<i>i</i>Pr₄}GaGaAr^{<i>i</i>Pr₄} with two equivalents of Mo­(CO)₅NMe₃ in THF solution. The mechanism of the reaction between Ar^{<i>i</i>Pr₄}GaGaAr^{<i>i</i>Pr₄} and Cr­(CO)₆ was probed computationally using density functional theory. The results suggest that the reaction proceeds via an intermediate monogallanediyl complex, Cr­(GaAr^{<i>i</i>Pr₄})­(CO)₅, that can be generated via two pathways, one of which involves the dimeric Ar^{<i>i</i>Pr₄}GaGaAr^{<i>i</i>Pr₄}, that are possibly competing. Ar^{<i>i</i>Pr₄}GaGaAr^{<i>i</i>Pr₄} was also shown to react readily under ambient conditions with Co₂(CO)₈ to give the monosubstituted dicobalt complex Co₂(μ-GaAr^{<i>i</i>Pr₄})­(μ-CO)­(CO)₆ by X-ray crystallography. The :GaAr^{<i>i</i>Pr₄} unit bridges the Co–Co bond unsymmetrically in the solid state. No evidence was found for incorporation of more than one :GaAr^<i>iPr</i>4 unit into the dicobalt complex

Counterintuitive Interligand Angles in the Diaryls E{C₆H₃‑2,6-(C₆H₂‑2,4,6‑^<i>i</i>Pr₃)₂}₂ (E = Ge, Sn, or Pb) and Related Species: The Role of London Dispersion Forces

The straightforward reaction of two equivalents of the lithium salt of the bulky terphenyl ligand Li­(OEt₂)­C₆H₃-2,6-(C₆H₂-2,4,6-^<i>i</i>Pr₃)₂ with suspensions of GeCl₂·dioxane, SnCl₂, or PbBr₂ in diethyl ether resulted in the isolation of the very crowded σ-bonded diaryl tetrylenes of formula E­{C₆H₃-2,6-(C₆H₂-2,4,6-^<i>i</i>Pr₃)₂}₂ (E = Ge (<b>1</b>), Sn (<b>2</b>), Pb (<b>3</b>)) as blue crystalline solids. Despite their high level of steric congestion, X-ray crystallography showed that compounds <b>1</b>–<b>3</b> possess C_ipso–E–C_ipso interligand bond angles in the range 107.61–112.55°, which are narrower than those observed in analogous species with less bulky terphenyl substituents. Compounds <b>1</b>–<b>3</b> were characterized by ¹H, ¹³C­{¹H} (<b>1</b>–<b>3</b>), and ¹¹⁹Sn­{¹H} (<b>2</b>) NMR spectroscopy, whereas solution ²⁰⁷Pb­{¹H} NMR spectroscopy of <b>3</b> has not yet afforded a signal under ambient conditions. FT-IR and UV–vis spectra of <b>1</b>–<b>3</b> were also recorded. The relatively narrow interligand angles displayed by <b>1</b>–<b>3</b> are attributed in part to the increase in London dispersion force interactions between the two Ar^<i>i</i>Pr6 (Ar^<i>i</i>Pr6 = -C₆H₃-2,6-(C₆H₂-2,4,6-^<i>i</i>Pr₃)₂) groups from carbon atoms in some of the isopropyl substituents and several carbon atoms from the flanking aryl rings. Density functional theory (DFT) calculations carried out at the PBE0/def2-QZVP level on the full series of diaryl tetrylenes, E­(Ar^<i>i</i>Pr6)₂, E­(Ar^<i>i</i>Pr4)₂ (Ar^<i>i</i>Pr4 = -C₆H₃-2,6-(C₆H₃-2,6-^<i>i</i>Pr₂)₂), and E­(Ar^Me6)₂ (Ar^Me6 = -C₆H₃-2,6-(C₆H₂-2,4,6-Me₃)₂, afford interaction energies as high as ca. 27 kcal mol^–1

Counterintuitive Interligand Angles in the Diaryls E{C₆H₃‑2,6-(C₆H₂‑2,4,6‑^<i>i</i>Pr₃)₂}₂ (E = Ge, Sn, or Pb) and Related Species: The Role of London Dispersion Forces

The straightforward reaction of two equivalents of the lithium salt of the bulky terphenyl ligand Li­(OEt₂)­C₆H₃-2,6-(C₆H₂-2,4,6-^<i>i</i>Pr₃)₂ with suspensions of GeCl₂·dioxane, SnCl₂, or PbBr₂ in diethyl ether resulted in the isolation of the very crowded σ-bonded diaryl tetrylenes of formula E­{C₆H₃-2,6-(C₆H₂-2,4,6-^<i>i</i>Pr₃)₂}₂ (E = Ge (<b>1</b>), Sn (<b>2</b>), Pb (<b>3</b>)) as blue crystalline solids. Despite their high level of steric congestion, X-ray crystallography showed that compounds <b>1</b>–<b>3</b> possess C_ipso–E–C_ipso interligand bond angles in the range 107.61–112.55°, which are narrower than those observed in analogous species with less bulky terphenyl substituents. Compounds <b>1</b>–<b>3</b> were characterized by ¹H, ¹³C­{¹H} (<b>1</b>–<b>3</b>), and ¹¹⁹Sn­{¹H} (<b>2</b>) NMR spectroscopy, whereas solution ²⁰⁷Pb­{¹H} NMR spectroscopy of <b>3</b> has not yet afforded a signal under ambient conditions. FT-IR and UV–vis spectra of <b>1</b>–<b>3</b> were also recorded. The relatively narrow interligand angles displayed by <b>1</b>–<b>3</b> are attributed in part to the increase in London dispersion force interactions between the two Ar^<i>i</i>Pr6 (Ar^<i>i</i>Pr6 = -C₆H₃-2,6-(C₆H₂-2,4,6-^<i>i</i>Pr₃)₂) groups from carbon atoms in some of the isopropyl substituents and several carbon atoms from the flanking aryl rings. Density functional theory (DFT) calculations carried out at the PBE0/def2-QZVP level on the full series of diaryl tetrylenes, E­(Ar^<i>i</i>Pr6)₂, E­(Ar^<i>i</i>Pr4)₂ (Ar^<i>i</i>Pr4 = -C₆H₃-2,6-(C₆H₃-2,6-^<i>i</i>Pr₂)₂), and E­(Ar^Me6)₂ (Ar^Me6 = -C₆H₃-2,6-(C₆H₂-2,4,6-Me₃)₂, afford interaction energies as high as ca. 27 kcal mol^–1