Nicole Arnold

Unprecedented Borane, Diborane(3), Diborene, and Borylene Ligands via Pt-Mediated Borane Dehydrogenation.

Reactions of an aryldihydroborane with a Pt(0) complex lead to a range of novel products, including complexes with bridging diborene and diborane(3) ligands and a complex with both borylene and borane (M → B) ligands. The products imply varying degrees of dehydrogenation of the boron centers with concomitant formation of boron-boron bonds, which in one case is later broken. These reactions show that although the dehydrocoupling of dihydroboranes is not a straightforward process in this case, the reactions are capable of connecting boron atoms in unusual ways, leading to unprecedented bonding motifs.

Desymmetrizing Electron-Deficient Diboranes(4): Diverse Products and Their Reactivity.

A comprehensive study of the reactivity of Lewis bases with dihalodiboranes(4) is presented. Diaryldihalodiboranes provide rearranged monoadducts when treated with cyclic (alkyl)(amino)carbenes, but halide-bridged adducts when treated with a range of pyridyl bases. Alternatively, the combination of diaminodihalodiboranes with strong carbene donors leads to boraborenium salts. The reduction and halide-abstraction reactivity of these adducts was also explored, leading to intramolecular C-H activation and the first 1,2-bis(borenium) dication.

Correlations and Contrasts in Homo- and Heteroleptic Cyclic (Alkyl)(amino)carbene-Containing Pt(0) Complexes.

An improved synthetic route to homoleptic complex [Pt(CAAC(Me))2] (CAAC = cyclic (alkyl)(amino)carbenes) and convenient routes to new heteroleptic complexes of the form [Pt(CAAC(Me))(PR3)] are presented. Although the homoleptic complex was found to be inert to many reagents, oxidative addition and metal-only Lewis pair (MOLP) formation was observed from one of the heteroleptic complexes. The spectroscopic, structural, and electrochemical properties of the zero-valent complexes were explored in concert with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. The homoleptic [Pt(CAAC)2] and heteroleptic [Pt(CAAC)(PR3)] complexes were found to be similar in their spectroscopic and structural properties, but their electrochemical behavior and reactivity differ greatly. The unusually strong color of the CAAC-containing Pt(0) complexes was investigated by TD-DFT calculations and attributed to excitations into the LUMOs of the complexes, which are predominantly composed of bonding π interactions between Pt and the CAAC carbon atoms.

N-Heterocyclic Silylenes in Boron Chemistry: Facile Formation of Silylboranes and Silaborinines

Reaction of a N-heterocyclic silylene (NHSi) with PhBX2 (X=Cl, Br) readily afforded six-membered silaborinines through an insertion/ring expansion sequence. Increasing the sterics of the borane from phenyl to duryl enabled the selective generation and isolation of the highly colored silylborane intermediates. Theoretical studies on the mechanism and energetics of the silaborinine formation were fully consistent with the experimental observations.

Controlling Regiochemistry in the Syntheses of Boraindanes from Diborane(4) Starting Materials

The reaction of tert-butylisonitrile (tBuNC) with 1,2-dihalo-1,2-diduryldiborane leads initially to the formation of the mono-base adduct of the symmetrical diborane(4), which then undergoes an intramolecular cyclization resulting in the formation of a 1-boraindane. This result is in contrast to a previously reported cyclization of a mono-isonitrile adduct of an unsymmetrical 1,1-pinacol-2,2-diaryldiborane(4), which results in the formation of a 1-boraindane. This latter result is herein confirmed by the reaction of 1,1-difluoro-2,2-dimesityldiborane(4) with tBuNC, which yielded the 2-boraindane compound. The mechanism of the former reaction has been computationally elucidated, and the differences between this route and the pathway to 1-boraindanes is discussed. These reactions further the understanding of the chemistry of the increasingly popular mono-base adducts of diborane(4), demonstrate the versatility of isonitriles in comparison to standard two-electron donors, and elucidate selective routes to boron-containing polycyclics, such as those being proposed as analogues for conventional organic pharmaceuticals.

Formation of a Trifluorophosphane Platinum(II) Complex by P−F Bond Activation of Phosphorus Pentafluoride with a Pt0 Complex

The reaction of PF5 with [(Cy3 P)2 Pt] gave the PF3 complex trans-[(Cy3 P)2 PtF(PF3 )][PF6 ], which was characterized by single-crystal X-ray diffraction, multinuclear NMR spectroscopy, and elemental analysis. To the best of our knowledge, this reaction is the first example of the oxidative addition of a P-F bond to a transition metal and is a rare example of an activation of a main-group-element-fluorine bond by a metal. Relativistic DFT calculations showed that the formation of the Lewis pair [(Cy3 P)2 Pt→PF5 ], which was not observed even at low temperatures, represents the initial step of the reaction. From this key intermediate, the cation trans-[(Cy3 P)2 PtF(PF3 )]+ was furnished by a two-step mechanism involving, successively, a second and a third PF5 molecule.

Bis(μ-diisopropyl-phosphanido-κ(2)P:P)bis-[hydrido(triisopropyl-phosphane-κP)platinum(II)].

In the centrosymmetric molecular structure of the title compound [Pt2(C6H14P)2H2(C9H21P)2], each PtII atom is bound on one side to a phosphane ligand (PiPr3) and a hydrido ligand. On the other side, it is bound to two phosphanide ligands (μ-PiPr2), which engage a bridging position between the two PtII atoms, forming a distorted square-planar structure motif. The Pt⋯Pt distance is 3.6755 (2) Å. A comparable molecular structure was observed for bis(μ-di-tert-butylphosphanido)bis[hydrido(triethylphosphane)platinum(II)] [Itazaki et al. (2004 ▶). Organometallics, 23, 1610–1621].