Matthias Stender

The synthesis and structure of sterically encumbered terphenyl tin(II) halide derivatives: simultaneous existence of monomers and dimers in the crystalline phase

Abstract The reaction of Et2O·LiC6H3-2,6–Trip2 (Trip=C6H2–2,4,6-i-Pr3) with SnCl2 afforded the two coordinate monomer Sn(Cl)C6H3-2,6–Trip2 (1), and its dimer {Sn(μ-Cl)C6H3–2,6-Trip2}2 (2), as orange and yellow crystals, respectively. Solution 119Sn NMR spectroscopy of 2 in C6D6 solution showed that it dissociated readily to give 1. The addition of pyridine (py) to a solution of 1 yielded the adduct py·Sn(Cl)C6H3–2,6-Trip2 (3) which featured tin in a three coordinate pyramidal environment. The reaction of the closely related bulky terphenyl lithium reagent LiC6H3–2,6-Dipp2 (Dipp=C6H3–2,6-i-Pr2) with SnCl2 afforded the mixed halide species {Sn(μ-Cl)0.35(μ-I)0.65C6H3–2,6-Dipp2}2 (4). This arose from the preparation of the lithium aryl precursor in situ from IC6H3–2,6-Dipp2 and n-BuLi. The monomeric nature of 1, and the weak association of 2 and 4, were attributed to the large size of the terphenyl ligands. All compounds were characterized by X-ray crystallography, 1H, 13C and 119Sn NMR spectroscopy, and IR and UV–Vis spectroscopy.

Reactions of M{N(SiMe3)2}2 (M=Mn, Fe or Co) with pyridine and 4,4′-bipyridyl: structural and magnetic studies

Abstract The reactions of the aromatic nitrogen donor ligands pyridine (py) and 4,4′-bipyridyl (4,4′-bipy) with the transition metal silylamides M{N(SiMe3)2}2 (M=Mn, Fe or Co) were investigated. Treatment of the metal amides with pyridine afforded the bispyridine complexes M{N(SiMe3)2}(py)2 (M=Mn, 1a; Fe, 2a; Co, 3a). Distillation or sublimation of 2a or 3a afforded the monopyridine complexes M{N(SiMe3)2}2(py) (M=Fe, 2b; Co, 3b). The addition of pyrazine (prz) to Mn{N(SiMe3)2}2 also yielded the bispyrazine adduct Mn{N(SiMe3)2}2(prz)2, 1b. However, the reaction of 4,4′-bipyridyl with Fe{N(SiMe3)2}2 or Co{N(SiMe3)2}2 afforded the polymeric chain-like complexes {M{N(SiMe3)2}2(4,4′-bipy)}∞ (M=Fe, 4; Co, 5). With the exception of 2b, all complexes were characterized by X-ray crystallography. The complexes 1a, 1b, 2a and 3a displayed monomeric structures and metal geometries that are based on a tetrahedron with interligand angles that deviate markedly from idealized values. Complex 3b was found to have a distorted trigonal planar geometry. In contrast, complexes 4 and 5 displayed polymeric zig-zag chain structures which have four coordinate metal centers connected by 4,4′-bipyridyl ligands. Magnetic studies indicated that complexes 1–3b have high-spin electron configurations and that the paramagnetic centers in 4 and 5 did not interact with each other through the 4,4′-bipyridyl ligands.

Unusual structures of lithium terphenyl derivatives

Abstract The synthesis, spectroscopic and structural characterization of three new lithium derivatives of terphenyl ligands are reported. These are the mixed lithium alkyl–lithium aryl compound {Li(t-Bu)LiC6H3-2,6-Trip2} (1, Trip=C6H2-2,4,6-i-Pr3), the dilithiated {LiC6H3-2-(C6H3-2-Me-5-t-Bu)-6-(C6H3-2-CH2Li-5-t-Bu)·Et2O}2 (2), and the ether solvated (Et2O)LiC6H3-2,6-(C6H4-4-t-Bu)2 (3). The synthesis of the terphenyl halide precursors for 2 and 3 is also given. The compound 1 resulted from the treatment of 1-IC6H3-2,6-Trip with two equivalents of Li(t-Bu) in hexane. It features the alkyl and aryl (terphenyl) groups bridged by two lithium ions. The lithium ions are further solvated by ortho aryl substituents and methyls of the t-Bu groups. This compound is a very rare example of a mixed lithium alkyl–lithium aryl species. Compound 2 was obtained in low yield from the treatment of 1-BrC6H3-2,6-(C6H3-2-Me-5-t-Bu)2 with two equivalents of Li(t-Bu). The terphenyl ligand was dilithiated by replacement of the bromine and a hydrogen from one of the methyl groups on the ortho aryl substituents. The ether solvated, dimeric, tetrametallic structure illustrated in the Table of Contents resulted. The compound 3 was obtained from the straightforward lithiation of the iodoterphenyl precursor in the presence of diethyl ether and features a lithium ion solvated by two ethers terminally bound to the ipso-carbon of the terphenyl group.

Anomalous structure–luminescence relationship in phosphorescent gold(I) isonitrile neutral complexes

A new compound that exhibits the shortest intermolecular Au...Au distance ever reported for neutral RNCAuX complexes is found to exhibit a counterintuitive higher-energy Au-centered phosphorescence than that in an analogous compound with a much longer Au...Au distance, presumably due to a different extent of excited-state distortion in dimers vs. extended chains.

The synthesis and structure of lithium derivatives of the sterically encumbered β-diketiminate ligand [{(2,6-Pri2H3C6)N(CH3)C}2CH]−, and a modified synthesis of the aminoimine precursor

The reaction of the β-aminoimine compound (2,6-Pri2H3C6)NC(CH3)CHC(CH3)N(C6H3-2,6-Pri2)H (1, Dipp2nacnacH; Dipp = C6H3-2,6-Pri2) with n-BuLi in diethyl ether or tetrahydrofuran afforded the solvates Dipp2nacnacLi(Et2O) (2) and Dipp2nacnacLi(THF) (3), respectively, which crystallized as monomers featuring the Li+ ions in a distorted trigonal planar environment and an essentially planar arrangement for the LiN2C3 ring. The lithiation of 1, in the absence of a donor solvent, afforded a Dipp2nacnacLi product that crystallized in two different types of associated structures, 4a and 4b. In the dimer 4a, the Li+ ion is coordinated to the two nitrogens of the Dipp2nacnac ligand, and it is associated by coordination of lithium to a carbon of the Dipp ring of the other Dipp2nacnac unit of the dimer. In the dodecamer 4b, the asymmetric unit consists of a chain of six LiDipp2nacnac units associated by interactions of the Li+ ions with one or two carbons from a Dipp ring of the next molecule in the chain. The hexamer is linked to an identical one (generated through an inversion center) by Li+–Dipp interactions involving the first and third lithium atoms from each hexamer, thereby generating an overall dodecameric structure of a type that was previously unknown for lithium salts. An improved yield synthesis for 1 was also developed.

Cation and hydrogen bonding effects on the self-association and luminescence of the dicyanoaurate ion, [Au(CN)2]−

The colorless salts [C5H10NH2][AuI(CN)2], [C4H8NH2][AuI(CN)2], [Ph2NNH3][AuI(CN)2]·H2O and [(n-C3H7)4N][AuI(CN)2]·H2O have been prepared by evaporation of aqueous solutions of potassium dicyanoaurate and the chloride salt of the appropriate cation. Hydrogen bonding between the cations and the cyano groups of the anions facilitates the formation of structures with strong aurophilic interactions between the anions. Thus, the [Au(CN)2]− ions self-associate in the three salts [C5H10NH2][AuI(CN)2] (Au⋯Au 3.0969(3) A), [C4H8NH2][AuI(CN)2] (Au1⋯Au2 3.0795(4) A), [Ph2NNH3][AuI(CN)2]·H2O (Au⋯Au 3.0866(4) A), while in [(n-C3H7)4N][AuI(CN)2]·H2O, which lacks N–H units, the gold ions are widely dispersed. The crystals of [C5H10NH2][AuI(CN)2], [C4H8NH2][AuI(CN)2] and [Ph2NNH3][AuI(CN)2]·H2O each show strong blue luminescence at room temperature, while [(n-C3H7)4N][AuI(CN)2]·H2O is non-luminescent.

Formation of [Ar*Ge{CH2C(Me)C(Me)CH2}CH2C(Me)]2 (Ar* = C6H3-2,6-Trip2; Trip = C6H2-2,4,6-i-Pr3) via reaction of Ar*GeGeAr* with 2,3-dimethyl-1,3-butadiene: evidence for the existence of a germanium analogue of an alkyne

The reduction of Ar*GeCl (Ar* = C6H3-2,6-Trip2; Trip = C6H2-2,4,6-i-Pr3) with one equivalent of potassium leads to the formation of a germanium analogue of an alkyne Ar*GeGeAr* 1; reaction of 1 with 2,3-dimethyl-1,3-butadiene yields [Ar*Ge(CH2C(Me)C(Me)CH2)CH2C(Me)=]2 2, which was structurally characterized.

Early/late heterobimetallics: unusual tetranuclear Zr/Ni and octanuclear Zr/Pd complexes with bridging bifunctional sulfidoacetato ligands

Unexpectedly the zirconocene metalloligand [Cp°2Zr(OOCCH2SH-κ1O)(OOCCH2SH-κ2O,O′)] (1; Cp° = C5EtMe4) reacts with [NiCl2(PMe2Ph)2] or [PdCl2(PnBu3)2] in the presence of NEt3 (ratio 1 ∶ 1 ∶ 2) to give the tetranuclear ZrIV–NiII complex 2 and the octanuclear ZrIV–PdII complex 3, respectively.

Nickelphosphankomplexe der Mercaptoessigsäure

The reaction of (Cp°2Zr(OOCCH2SH-κ 1 O)- (OOCCH2SH-κ 2 O,O)) (Cp° C5EtMe4) with (NiCl2(PMe2Ph)2) or (NiCl2(dppe)) (dppe PPh2CH2CH2PPh2) in the presence of NEt3 yields the tetranuclear Zr IV /Ni II complex ({Cp°2Zr- (κ 1 O-OOCCH2S-κ 2 O,S)(κ 2 O,O-OOCCH2S-κ 1 S)Ni(PMe2Ph)}2) (1) and the chelate complexes (Ni(OOCCH2S-κ 2 O,S)L2 )( L PMe2Ph (2), L2 dppe (3)). 2 and 3 are also accessible from (NiCl2(PMe2Ph)2) or (NiCl2(dppe)) and mercaptoacetic acid in the