Reinvestigation of Reactions of HgPh2 with Eu and Yb Metal and the Synthesis of a Europium(II) Bis(tetraphenylborate).

Europium bis(tetraphenylborate) [Eu(thf)7][BPh4]2⋅thf containing a fully solvated [Eu(thf)7]2+ cation, was synthesized by protolysis of "EuPh2" (from Eu and HgPh2) with Et3NHBPh4, and the structure was determined by single-crystal X-ray diffraction. Efforts to characterize the putative "Ph2Ln" (Ln = Eu, Yb) reagents led to the synthesis of a mixed-valence complex, [(thf)3YbII(µ-Ph)3YbIII(Ph)2(thf)]⋅2thf, resulting from the reaction of Yb metal with HgPh2 at a low temperature. This mixed-valence YbII/YbIII compound was studied by 171Yb-NMR spectroscopy and single-crystal X-ray diffraction, and the oxidation states of the Yb atoms were assigned.

Linear MgCp*2 vs Bent CaCp*2: London Dispersion, Ligand-Induced Charge Localizations, and Pseudo-Pregostic C-H···Ca Interactions.

In the family of metallocenes, MgCp*2 (Cp* = pentamethylcyclopentadienyl) exhibits a regular linear sandwich structure, whereas CaCp*2 is bent in both the gas phase and solid state. Bending is typically observed for metal ions which possess a lone pair. Here, we investigate which electronic differences cause the bending in complexes lacking lone pairs at the metal atoms. The bent gas-phase geometry of CaCp*2 suggests that the bending must have an intramolecular origin. Geometry optimizations with and without dispersion effects/d-type polarization functions on MCp2 and MCp*2 gas-phase complexes (M = Ca, Mg) establish that attractive methyl···methyl London dispersion interactions play a decisive role in the bending in CaCp*2. A sufficient polarizability of the metal to produce a shallow bending potential energy curve is a prerequisite but is not the reason for the bending. Concomitant ligand-induced charge concentrations and localizations at the metal atoms are studied in further detail, for which real-space bonding and orbital-based descriptors are used. Low-temperature crystal structures of MgCp*2 and CaCp*2 were determined which facilitated the identification and characterization of intermolecular pseudo-pregostic interactions, C-H···Ca, in the CaCp*2 crystal structure.

Lanthanoid Pseudo-Grignard Reagents: A Major Untapped Resource.

Pseudo-Grignard reagents PhLnI (Ln=Yb, Eu), readily prepared by the oxidative addition of iodobenzene to ytterbium or europium metal at -78 °C in tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME), react with a range of bulky N,N'-bis(aryl)formamidines to generate an extensive series of LnII or more rarely LnIII complexes, namely [Eu(DippForm)I(thf)4 ]⋅thf (1), [{EuI2 (dme)2 }2 ] (2), [Eu(XylForm)I(dme)2 ]⋅0.5 dme (3 a), [Eu(XylForm)I(dme)(µ-dme)]n (3 b), [{Eu(XylForm)I(µ-OH)(thf)2 }2 ] (4), [Yb(DippForm)I(thf)3 ]⋅thf (5 a), [Yb(DippForm)I2 (thf)3 ]⋅2 thf (5 b), [{Yb(MesForm)I(thf)2 }2 ] (6), [{Yb(XylForm)I(thf)2 }2 ] (7 a), and [Yb(XylForm)2 I(dme)]⋅dme (7 b) {(Form=ArNCHNAr; XylForm (Ar=2,6-Me2 C6 H3 ), MesForm (Ar=2,4,6-Me3 C6 H2 ), DippForm (Ar=2,6-iPr2 C6 H3 )}. Reaction of PhEuI and MesFormH in DME consistently gave 2, and reaction with XylFormH in THF gave 4. Europium complexes 1 and 3 a are seven-coordinate divalent monomers, whilst 3 b is a seven-coordinate dme-bridged polymer. Complex 5 a of the smaller YbII is a six-coordinate monomer, but the related 6 and 7 a are six-coordinate iodide-bridged dimers. 4 is a trivalent seven-coordinate hydroxide-bridged dimer, whereas complexes 5 b and 7 b are seven-coordinate monomeric YbIII derivatives. A characteristic structural feature is that iodide ligands are cisoid to the formamidinate ligand. To illustrate the synthetic scope of the pseudo-Grignard reagents, [Yb(Ph2 pz)I(thf)4 ] (Ph2 pz=3,5-diphenylpyrazolate) was oxidised with 1,2-diiodoethane to afford seven-coordinate monomeric pyrazolato-ytterbium(III) iodide [Yb(Ph2 Pz)I2 (thf)3 ] (8) in high yield, whilst metathesis between [Yb(Ph2 pz)I(thf)4 ] and NaCp (Cp=C5 H5 ) gave [Yb(C5 H5 )(Ph2 pz)(thf)]n (9), a nine-coordinate η5 :η5 -Cp-bridged coordination polymer. Reaction of the pseudo-Grignard reagent MeYbI with KN(SiMe3 )2 gave [K(dme)4 ][Yb{N(SiMe3 )2 }3 ] (10) with a charge-separated three-coordinate homoleptic [Yb{N(SiMe3 )2 }3 ]- anion, a complex that could be obtained in high yield by deliberate synthesis from YbI2 and KN(SiMe3 )2 in DME.

Organolanthanoid-halide synthons--a new general route to monofunctionalized lanthanoid(II) compounds?

New Eu(II) and Yb(II) complexes [Ln(Ph(2)pz)I(thf)(4)] were synthesized from the corresponding metals and 3,5-diphenylpyrazole (HPh(2)pz) using iodobenzene as oxidizing agent. In the absence of the pyrazole, the charge separated Yb(II)/Yb(III) complex [{Yb(dme)(4)}{YbPh(4)(dme)}(2)] has been isolated.

An unusual barium olefin complex.

Reacting [(eta5-C5Me5)In] in the presence of [(eta5-C5Me5)2Ba] results in the C-H activation of the barocene ligand framework. A barium metallocene with an intramolecular barium-olefin bond was formed.

Gallium(I)-alkaline earth metal donor-acceptor bonds.

Compounds with a gallium-alkaline earth metal bond, [(eta(5)-C(5)Me(5))(2)Ca-Ga(eta(5)-C(5)Me(5))], [(eta(5)-C(5)Me(5))(2)(THF)Sr-Ga(eta(5)-C(5)Me(5))], and [(eta(5)-C(5)Me(5))(2)Ba-{Ga(eta(5)-C(5)Me(5))}(2)], were prepared.

Zirconium complexes having a chiral phosphanylamide in the co-ordination sphere.

The chiral phosphanylamido ligand, (N(CHMePh)(PPh2))-, has been introduced into co-ordination chemistry. As starting material the oily amines HN(R-*CHMePh)(PPh2)(1a) and HN(S-*CHMePh)(PPh2)(1b) were used. To reconfirm their absolute structure, 1b was oxidized with H2O2 in air to obtain HN(S-*CHMePh)(P(O)Ph2)(2) as a solid compound. The solid-state structure of 2 was established by single-crystal X-ray diffraction. The lithium salts of both enantiomers Li(N(R-*CHMePh)(PPh2))(3a) and Li(N(S-*CHMePh)(PPh2))(3b) were prepared by deprotonation reaction of 1a,b. Compounds 3a,b were further reacted with zirconocen dichloride to give the chiral metallocenes [(eta5-C5H5)2Zr(Cl)(eta2-N(R-*CHMePh)(PPh2))](4a) and [(eta5-C5H5)2Zr(Cl)(eta2-N(S-*CHMePh)(PPh2))](4b). In an alternative approach to give chiral zirconium compounds, the neutral amine 1b was reacted with [(PhCH2)4Zr] to give the enantiomeric pure complex [(PhCH2)3Zr(eta2-N(S-*CHMePh)(PPh2))](5). The solid-state structures of all zirconium complexes were determined by single-crystal X-ray diffraction.