Stable compounds featuring gold-boron bonds are rare, and until 2006, were limited to those containing hypercoordinate boron ligands, for example, polymetallic monoboron clusters [1] and complexes in which a {LAu + } fragment formally bridges an apical boron atom of a carborane cluster and another metal atom.[2] Linking low-coordinate boron to gold has proved a challenging task, but this has recently been shown to reflect little more than a synthetic roadblock. Traditional methods for constructing transition-metal-boron bonds (based on B + /M À polarity) [3] were found to be unsuitable: Au I appears to lack sufficient reducing strength or nucleophilicity to perturb boron-halide bonds or to donate to an nonbridging Lewis acidic borane. Synthetic strategies based on the opposite polarity (B À /M + ) were unthinkable until very recently, because of the absence of boron-based nucleophiles.[4] In the last three years, success has been found with both of these strategies, and two new boron-gold coordination modes have been discovered, namely the borane gold complexes (Au!B), and the boryl gold complexes (Au ! B), by the groups of Bourissou, [5] and Yamashita and Nozaki, [4b] respectively. Unlike the earlier complexes, these two new bonding patterns are considered to be classical two-center-two-electron interactions, adding to their novelty. [6] The borane gold complexes feature one or more tethered phosphine groups binding orthogonally to the boron-gold axis (B-Au-L: 79-848, L = chelating phosphino group), while in the boryl gold complexes, the B-Au-L (L = phosphine, Nheterocyclic carbene) axis is effectively linear. [4b, 5] There is a correspondingly large difference between the AuÀB distances of borane gold complexes (2.32-2.66 ) and those of boryl gold complexes (2.08-2.09 ). These structural patterns correlate well with the generally accepted understanding of the boryl ligand as a pure s-donor, and the borane ligand as a pure s-acceptor. Herein we experimentally and theoretically examine the structure of an unusual dimanganese boryl gold complex with a bonding situation that is not described correctly by either of the abovementioned patterns.The(1, dme = 1,2-dimethoxyethane; Scheme 1), and its nucleophilic reactivity with methyl iodide, were reported recently.[7] The tendency for lowvalent late-transition-metal fragments (such as {M(PCy 3 )}, M = Pd, Pt) to undergo addition to metal-borylene bonds is now well-documented, [8] and accordingly we were interested in the reactivity of 1 towards late-transition-metal halide complexes.Stirring of gold carbene complex [(ITol)AuCl] (ITol = N,N'-bis(4-methylphenyl)imidazol-2-ylidene) with 1 in toluene at room temperature resulted in a color change from paleyellow to orange, and a moderate downfield shift of the broad 11 B NMR signal to d B = 209 ppm (Scheme 1).[9] The position of this signal is in stark contrast to those of the trimetallic boron systems containing M!B dative bonds [(h 5 -C 5 [10a] The signal also correlates well with the family of anionic, neutral, and ...

In early reports, the boron atom of the anionic borido complexes [{(η(5)-C(5)H(4)R)(OC)(2)Mn}(2)B](-) (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(PCy(3))(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.

The realization of molecular boron species in which all valences are saturated by electron-precise bonds to d-block metals marks a significant recent development in borylene complex chemistry.[1] This group of species, which display "naked" boron À that is, a boride À as ligand, comprises neutral (e.g. 1), [2;3] cationic (3-5), [4;5] and even anionic metalloborylenes (2) [6] with sp-hybridized two-coordinate boron centers as well as trimetalloboranes (6) that are derived from trigonal-planar, sp 2 -hybridized boron [7] (Scheme 1). With the aim of increasing the number of metal-boron bonds by subsequent oxidative addition of BÀBr bonds, [8]

You may now kiss the boride: Four‐coordinate boron, carbon, and nitrogen are almost always tetrahedral. The first examples of compounds with near‐planar four‐coordinate boron atoms have been prepared from trinuclear coordinatively unsaturated borido complexes. The two resultant tetranuclear complexes (see scheme) both feature near‐planar four‐coordinate boron atoms, with angle sums of 362.4° and 364.6°.