Intramolecular Nucleophilic Substitution on Coordinated Borabenzenes: A New Entry into Boratabenzene Complexes

Unique Double and Triple Decker Arrangements of Rare-Earth 9,10-Diborataanthracene Complexes Featuring Single-Molecule Magnet Characteristics

Herein, we present the first report on the synthesis of rare-earth complexes featuring a 9,10-diborataanthracene ligand. This 14-π-electron ligand is highly reductive and was previously used in small-molecule activation. Salt elimination reactions between dipotassium 9,10-diethyl-9,10-diborataanthracene [K2(DEDBA)] and [LnIII(η8-CotTIPS)(BH4)(thf)x] (CotTIPS=1,4-(iPr3Si)2C8H6) in a 1 : 1 ratio yielded heteroleptic sandwich complexes [K(η8-CotTIPS)LnIII(η6-DEDBA)] (Ln=Y, Dy, Er). These compounds form Lewis-base-free one-dimensional coordination polymers when crystallised from toluene. In contrast, reaction of [K2(DEDBA)] and [LnIII(η8-CotTIPS)(BH4)(thf)x] in a 1 : 2 ratio led to the formation of heteroleptic triple-decker complexes [(η8-CotTIPS)LnIII(μ-η6:η6-DEDBA)LnIII(η8-CotTIPS)] (Ln=Y, Dy, Er). Notably, these are not only the first lanthanide triple-decker compounds featuring a six-membered ring as a deck but also the first trivalent lanthanide triple-decker featuring a heterocycle in the coordination sphere. Magnetic investigations reveal that [K(η8-CotTIPS)LnIII(η6-DEDBA)] (Ln=Dy, Er) and [(η8-CotTIPS)ErIII(μ-η6:η6-DEDBA)ErIII(η8-CotTIPS)] exhibit Single-Molecule Magnet (SMM) behaviour. In the case of [(η8-CotTIPS)LnIII(μ-η6:η6-DEDBA)LnIII(η8-CotTIPS)] (Ln=Dy, Er), the introduction of a second near lanthanide ion results in strong antiferromagnetic interactions, allowing the enhancement of the magnetic characteristic of the system, compared to the quasi isolated counterpart. This research renews the overlooked coordination chemistry of the DBA ligand and expands it to encompass rare-earth elements.

(Boratabenzene)(cyclooctatetraenyl) lanthanide complexes: a new type of organometallic single-ion magnet

(Boratabenzene)(cyclooctatetraenyl) lanthanide complexes were synthesized, and the erbium ones showed single-ion magnet behaviours. One complex exhibited hysteresis up to 8 K, and another one featured energy barrier of 300 cm⁻¹.

Phosphidoboratabenzene-rhodium(i) complexes as precatalysts for the hydrogenation of alkenes at room temperature and atmospheric pressure

The di-tert-butylphosphido-boratabenzene ligand (DTBB) reacts with [(C2H4)2RhCl]2 yielding the dimeric species [(C2H4)Rh(DTBB)]2 (1). This species was fully characterized by multinuclear NMR and X-ray crystallography. Complex 1 readily dissociates ethylene in solution and upon exposure to 1 atm of H2 is capable of carrying out the hydrogenation of ethylene. The characterization of two Rh-H species by multinuclear NMR spectroscopy is provided. The reactivity of 1 towards the catalytic hydrogenation of alkenes and alkynes at room temperature and 1 atm of H2 is reported and compared to the activity of Wilkinson's catalyst under the same reaction conditions.

Mono(boratabenzene) rare-earth metal dialkyl complexes: synthesis, structure and catalytic behaviors for styrene polymerization

Four mono(boratabenzene) rare-earth metal dialkyl complexes, [(3,5-Me2-C5H3BR)Ln(CH2SiMe3)2(THF)] (1: R = NEt2, Ln = Sc; 2: R = NEt2, Ln = Lu; 3: R = Ph, Ln = Sc; 4: R = Ph, Ln = Lu), were synthesized efficiently via a one-pot strategy with Li[3,5-Me2-C5H3BR] (R = NEt2, Ph), LnCl3(THF)x (Ln = Sc, x = 3; Ln = Lu, x = 0), and LiCH2SiMe3. The solid-state structures of 1 and 2 were determined by single-crystal X-ray diffraction. Variable-temperature NMR studies indicated that the energy barrier for the rotation of aminoboratabenzene in 1 (ΔG‡ ≈ 71 kJ mol−1) is higher than that of phenylboratabenzene in 3 (ΔG‡ ≈ 59 kJ mol−1). These mono(boratabenzene) rare-earth metal dialkyl complexes’ catalytic behaviors for styrene polymerization were investigated, and found that mono(boratabenzene) scandium dialkyl complexes show high catalytic activities for syndiotactic polymerization upon activation with cocatalysts.

Coordinating Anions: (Phosphino)tetraphenylborate Ligands as New Reagents for Synthesis

Anionic, electron-releasing phosphines that incorporate a borate counteranion within the ligand framework are promising reagents for organometallic catalysis. This report describes the synthesis of a new class of monodentate tertiary phosphines built upon the commonly employed tetraphenylborate anion. These new phosphines are highly stable and strongly electron-releasing and readily coordinate transition metals. Moreover, they are promising reagents for catalysis, as demonstrated by their ability to promote the Suzuki cross-coupling of aryl chloride substrates.

Synthesis and structural characterization of 2,6-dimesitylphenyl complexes of scandium, ytterbium, and yttrium

The molecular structures of a number of 2,6-dimesitylphenyl-based (2,6-dimesitylphenyl = Dmp) complexes of the group 3 elements scandium and yttrium as well as of the lanthanide element ytterbium are reported. Reaction of 1 equiv of DmpLi with 1 equiv of MCl(3) (M = Sc, Yb, Y) in tetrahydrofuran at room temperature followed by crystallization from toluene/hexanes at -30 degrees C produces DmpMCl(2)(THF)(2) (M = Sc: 1; M = Yb: 2) and DmpMCl(2)(THF)(3) (M = Y: 3), respectively. The one-pot reaction of DmpLi with 1 equiv of YbCl(3) in tetrahydrofuran at room temperature followed by addition of 1 equiv of KO(t)Bu produces the heterobimetallic monoalkoxide complex DmpYb(THF)(O(t)Bu)(mu-Cl)(2)Li(THF)(2) (4), which was crystallized from toluene/tetrahydrofuran (20:1) at -30 degrees C. Crystal data for 1: monoclinic, P2(1)/n; T = 203 K; a = 10.178(3) A; b = 15.468(3) A; c = 20.132(5) A; beta = 101.85(3) degrees; V = 3102.0(17) A(3); Z' = 4; D(calcd) = 1.228 g cm(-3); R(1) = 5.89%. Crystal data for 2: monoclinic, P2(1)/n; T = 173 K; a = 10.2447(7) A; b = 15.5683(12) A; c = 20.0979(14) A; beta = 101.749(4) degrees; V = 3238.3(5) A(3); Z' = 4; D(calcd) = 1.485 g cm(-3); R(1) = 4.32%. Crystal data for 3: monoclinic, P2(1)/n; T = 203 K; a = 15.950(3) A; b = 11.865(2) A; c = 18.254(3) A; beta = 92.323(3) degrees; V = 3451.9(10) A(3); Z' = 4; D(calcd) = 1.327 g cm(-)(3); R(1) = 4.43%. Crystal data for 4: triclinic, P1; T = 193 K; a = 10.2252(2) A; b = 11.3497(2) A; c = 18.5814(2) A; alpha = 98.7353(6) degrees; beta = 102.8964(6) degrees; gamma = 94.8058(5) degrees; V = 2062.09(5) A(3); Z' = 2; D(calcd) = 1.375 g cm(-3); R(1) = 4.56%. The molecular structures of 1-3 feature monomeric complexes with distorted trigonal-bipyramidal (1 and 2) or octahedral (3) coordination geometry about the metal atom, with the two chlorine atoms occupying the axial positions. 4 represents the first example of an alkoxide derivative of a terphenyl lanthanide complex. The molecular structure of the ate complex 4 exhibits a heavily distorted trigonal-bipyramidal coordination polyhedron about the ytterbium atom, with one of the mu-chlorine atoms and the oxygen atom of the tetrahydrofuran ligand representing the axial positions of the trigonal-bipyramidal arrangement. A terminal alkoxide ligand is another main feature of the molecular structure of complex 4.

Three conformational polymorphs of di-mu-chlorotetrakis(1-methylboratabenzene)diyttrium: synthesis, x-ray structures, quantum chemical calculations, and lattice energy minimizations

The reaction of yttrium trichloride with lithium 1-methylboratabenzene (1/2) in toluene (110 degrees C, 3 days) afforded the donor-free dinuclear sandwich complex [(C(5)H(5)BMe)(2)Y(mu-Cl)](2) (1) in 85% yield as pale-yellow crystals. By means of single crystal and powder diffraction methods, three conformational polymorphs, alpha-1 [P2(1)/n (No. 14), monoclinic, a = 6.6124(8) A, b = 14.352(9) A, c = 14.120(1) A, beta = 95.57(1) degrees, V = 1333.7(9) A(3), Z = 2], beta-1 [P2(1)/a (No. 14), monoclinic, a = 8.542(2) A, b = 13.712(6) A, c = 11.76(1) A, beta = 102.60(4) degrees, V = 1344.5(13) A(3), Z = 2], and gamma-1 [Pbca (No. 61), orthorhombic, a = 20.091(5) A, b = 13.527(3) A, c = 9.976(2) A, V = 2711.2(11) A(3), Z = 4], were characterized in the solid state of 1. The molecules in the three phases vary remarkably in the rotational position of boratabenzene ligands with differences of 91.1, 133.1, and 24.9 degrees between each pair. DFT calculations at the B3LYP/LanL2DZ level reveal that the three molecular structures observed in the solid state correspond closely to three minima on the gas-phase potential energy surface. The beta conformation is 2.8 and 7.2 kJ/mol more stable than the alpha and gamma conformations, respectively. Lattice energy minimizations predict that the alpha-1 phase is about 5.5 and 18.7 kJ mol(-)(1) more stable than the beta-1 and gamma-1 modifications, in agreement with the packing coefficients and the molecular volumes of the three crystal structures. While the alpha-1 and beta-1 modifications have comparable total energies, the gamma-1 form is less stable. The total energy differences among the polymorphs are greater than generally expected.