Complete and Partial 1,2-Additions across Transition Metal–Boron Double Bonds

The first 1,2-additions across a metal–boron double bond are reported, one a definitive chlorogallation of a FeB bond, the other a partial chlorogallation of a MoB bond that leads to a highly unusual, planar Mo–B–Ga–Cl rhombus. The two reactions occur with opposite regiochemistry, with the Ga atom bound to the Fe atom in the former and to both the Mo and B atoms in the latter. The bonding in the Mo adduct and the reasons for the differing regiochemistry of the reaction are explored computationally

Complete and Partial 1,2-Additions across Transition Metal–Boron Double Bonds

The first 1,2-additions across a metal–boron double bond are reported, one a definitive chlorogallation of a FeB bond, the other a partial chlorogallation of a MoB bond that leads to a highly unusual, planar Mo–B–Ga–Cl rhombus. The two reactions occur with opposite regiochemistry, with the Ga atom bound to the Fe atom in the former and to both the Mo and B atoms in the latter. The bonding in the Mo adduct and the reasons for the differing regiochemistry of the reaction are explored computationally

Ditopic Ambiphilicity of an Anionic Dimetalloborylene Complex

In early reports, the boron atom of the anionic borido complexes [{(η⁵-C₅H₄R)­(OC)₂Mn}₂B]⁻ (R = H, Me) showed nucleophilic behavior in the presence of electrophiles such as methyl iodide and group 11 metal chlorides, akin to the ground-breaking boryl lithium of Yamashita and Nozaki. Later, a reaction with the well-known transition metal Lewis base [Pt­(PCy₃)₂] suggested the possibility of boron-centered electrophilicity. In this paper we elucidate a third reactivity profile of the anion, nucleophilic substitution on heavier halides of group 14 metals by a manganese center. Meanwhile, other group 11 halides were found to interact with the boron center, but form structures different from those seen with gold. The basis of the discrimination of the anion between main group and transition metal halides is explored computationally, and the ditopic, ambiphilic reactivity of the anions is discussed

Ditopic Ambiphilicity of an Anionic Dimetalloborylene Complex

In early reports, the boron atom of the anionic borido complexes [{(η⁵-C₅H₄R)­(OC)₂Mn}₂B]⁻ (R = H, Me) showed nucleophilic behavior in the presence of electrophiles such as methyl iodide and group 11 metal chlorides, akin to the ground-breaking boryl lithium of Yamashita and Nozaki. Later, a reaction with the well-known transition metal Lewis base [Pt­(PCy₃)₂] suggested the possibility of boron-centered electrophilicity. In this paper we elucidate a third reactivity profile of the anion, nucleophilic substitution on heavier halides of group 14 metals by a manganese center. Meanwhile, other group 11 halides were found to interact with the boron center, but form structures different from those seen with gold. The basis of the discrimination of the anion between main group and transition metal halides is explored computationally, and the ditopic, ambiphilic reactivity of the anions is discussed

Strained <i>ansa</i> Half-Sandwich Complexes of Ruthenium and Osmium and a Non-Iron Metallopolymer by Ring-Opening Polymerization

Herein we report the first non-iron polymer obtained from an <i>ansa</i> half-sandwich complex. This polymeric organometallic material was obtained from a new disilanediyl-bridged ruthenium complex upon thermally induced ring-opening polymerization (ROP). Additionally, a corresponding distannanediyl-bridged osmium species is reported, the first example of an <i>ansa</i> half-sandwich complex of this element

Electronic and Structural Effects of Stepwise Borylation and Quaternization on Borirene Aromaticity

Room-temperature photolysis of the aminoboryl complex [(OC)₅CrBN­(SiMe₃)₂] in the presence of a series of mono- or bis­(boryl) alkynes bis­{bis­(dimethylamino)­boryl}­ethyne, 1-phenyl-2-bis­(dimethylamino)­borylethyne, and 1-trimethylsilyl-2-bis­(dimethylamino)­borylethyne led to the isolation of hitherto unknown borylborirenes in resonable yields, that is, [(RCCR′)­(μ-BN­(SiMe₃)₂)] (<b>7</b>, R = B­(NMe₂)₂, R′ = Ph; <b>8</b>, R = R′ = B­(NMe₂)₂; <b>9</b>, R = B­(NMe₂)₂, R′ = SiMe₃). The borirenes were isolated and spectroscopically characterized by multinuclear NMR, IR, and UV/vis spectroscopy, crystallography, and elemental analysis. Reactivity studies of the borirenes demonstrated their behavior toward different Lewis bases. The isolated adducts and the parent borirenes were compared to 1,3-mesityl-2-phenylborirene and its adducts. To gain insight into the electronic structure and to evaluate the influence of the exocyclic groups, Density Functional Theory (DFT) calculations were carried out

Efficient Ni^II₂Ln^III₂ Electrocyclization Catalysts for the Synthesis of <i>trans</i>-4,5-Diaminocyclopent-2-enones from 2‑Furaldehyde and Primary or Secondary Amines

A series of heterometallic coordination clusters (CCs) [Ni^II₂Ln^III₂(L1)₄Cl₂(CH₃CN)₂] 2CH₃CN [Ln = Y (<b>1Y</b>), Sm (<b>1Sm</b>), Eu (<b>1Eu</b>), Gd (<b>1Gd</b>), or Tb (1<b>Tb</b>)] were synthesized by the reaction of (E)-2-(2-hydroxy-3-methoxybenzylidene-amino)­phenol) (H₂L1) with NiCl₂·6­(H₂O) and LnCl₃·x­(H₂O) in the presence of Et₃N at room temperature. These air-stable CCs can be obtained in very high yields from commercially available materials and are efficient catalysts for the room-temperature domino ring-opening electrocyclization synthesis of <i>trans</i>-4,5-diaminocyclopent-2-enones from 2-furaldehyde and primary or secondary amines under a non-inert atmosphere. Structural modification of the catalyst to achieve immobilization or photosensitivity is possible without deterioration in catalytic activity

Experimental Assessment of the Strengths of B–B Triple Bonds

Diborynes, molecules containing homo­atomic boron–boron triple bonds, have been investigated by Raman spectroscopy in order to determine the stretching frequencies of their central BB units as an experimental measure of homoatomic bond strengths. The observed frequencies between 1600 and 1750 cm^–1 were assigned on the basis of DFT modeling and the characteristic pattern produced by the isotopic distribution of boron. This frequency completes the series of known stretches of homoatomic triple bonds, fitting into the trend established by the long-known stretching frequencies of CC and NN triple bonds in alkynes and dinitrogen, respectively. A quantitative analysis was carried out using the concept of relaxed force constants. The results support the classification of the diboryne as a true triple bond and speak to the similarities of molecules constructed from first-row elements of the p block. Also reported are the relaxed force constants of a recently reported diborabutatriene, which again fit into the trend established by the vibrational spectroscopy of organic cumulenes. As part of these studies, a new diboryne with decreased steric bulk was synthesized, and a computational study of the rotation of the stabilizing ligands indicated alkyne-like electronic isolation of the central B₂ unit