Synthesis of the First Heteroaryl-Substituted Boryl Complexes: Strong Stabilizing Effects of Boron–Aryl π‑Conjugation

The first examples of heteroarylboryl complexes were prepared and have been found to be unreactive toward a range of strong reductants, strong Lewis bases, and halide-abstraction reagents. The inertness of the complexes is attributed to strong π-conjugation between the π-basic heteroaryl groups and the π-acidic boron atom. This hypothesis is supported by comparison of the structural and spectroscopic properties of the heteroarylboryl complexes with analogous previously reported homoarylboryl complexes, with the former showing greater coplanarity of the aryl ring with the boron atom and much less facile reactivity

A Simple Decarbonylative Route to Heterodinuclear Alkylborylene Complexes

A new, photolytic route to heterodinuclear alkylborylene complexes is presented using the terminal manganese borylene complex [(η⁵-C₅H₅)­(OC)₂Mn­(B<i>t</i>Bu)]. Using this route, three new heterodinuclear alkylborylene complexes were prepared (Mn/Cr and Mn/Co), in addition to a known dimanganese alkylborylene complex usually prepared by salt elimination. The complexes have been characterized by NMR and IR spectroscopy as well as single-crystal X-ray crystallography. The overall picture gained from the spectroscopic and structural data is that the two metals in the Mn/Cr and Mn/Mn complexes appear to share the boron atom more evenly, while the cobalt fragment in the Mn/Co complex is more loosely bound to the boron atom

Structure and Reactivity of Distanna[2]metallocenophanes of Ruthenium and Osmium

We report the molecular structures of 1,1′-dilithiometallocenes of ruthenium and osmium. These compounds served as precursors for the synthesis and subsequent structural characterization of the first [2]­osmocenophanes with disilane and distannane bridges, as well as of a distanna[2]­ruthenocenophane. In addition, the insertion of sulfur and selenium into the Sn–Sn bridges was studied and it was observed that the presence of the Lewis base pmdta (<i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>″,<i>N</i>″-pentamethyldiethylenetriamine) dramatically accelerates the reaction

New Metal-Only Lewis Pairs: Elucidating the Electronic Influence of <i>N</i>-Heterocyclic Carbenes and Phosphines on the Dative Pt-Al Bond

The synthesis and full characterization of a new heteroleptic <i>N</i>-heterocyclic carbene (NHC)–phosphine platinum(0) complex and formation of its corresponding alane adduct is reported. The influence of the ligands on the Lewis basic properties was studied via multinuclear NMR-spectroscopy, X-ray analyses, and density functional theory (DFT) calculations. Consistently, the effect of changing the halogens upon the Lewis acid properties of aluminum halides was studied by X-ray analysis and DFT calculations

Tin-Bridged <i>ansa</i>-Metallocenes of the Late Transition Metals Cobalt and Nickel: Preparation, Molecular and Electronic Structures, and Redox Chemistry

Using the flytrap approach, paramagnetic <i>ansa</i>-metallocenes of the late transition metals cobalt and nickel containing a tetra-<i>tert</i>-butyldistannane bridge have been prepared. The complexes were identified using a combination of analytical methods (NMR, EPR, cyclic voltammetry, and X-ray crystallography) and further converted to their corresponding cations by one-electron oxidation with ferrocenium hexafluorophosphate. Spectral and structural analyses of the ionic products are consistent with metal-based oxidations

New Metal-Only Lewis Pairs: Elucidating the Electronic Influence of <i>N</i>-Heterocyclic Carbenes and Phosphines on the Dative Pt-Al Bond

The synthesis and full characterization of a new heteroleptic <i>N</i>-heterocyclic carbene (NHC)–phosphine platinum(0) complex and formation of its corresponding alane adduct is reported. The influence of the ligands on the Lewis basic properties was studied via multinuclear NMR-spectroscopy, X-ray analyses, and density functional theory (DFT) calculations. Consistently, the effect of changing the halogens upon the Lewis acid properties of aluminum halides was studied by X-ray analysis and DFT calculations

Tin-Bridged <i>ansa</i>-Metallocenes of the Late Transition Metals Cobalt and Nickel: Preparation, Molecular and Electronic Structures, and Redox Chemistry

Using the flytrap approach, paramagnetic <i>ansa</i>-metallocenes of the late transition metals cobalt and nickel containing a tetra-<i>tert</i>-butyldistannane bridge have been prepared. The complexes were identified using a combination of analytical methods (NMR, EPR, cyclic voltammetry, and X-ray crystallography) and further converted to their corresponding cations by one-electron oxidation with ferrocenium hexafluorophosphate. Spectral and structural analyses of the ionic products are consistent with metal-based oxidations

Investigation of Steric Factors Involved in the Formation of Terminal Cationic Platinum Arylborylene Complexes

The abstraction of halido ligands from Pt^II diphosphine boryl complexes has previously been shown to yield one of two isomeric products: either T-shaped cationic boryl complexes or square-planar cationic borylene complexes. However, the latter product has only been observed in one case, that of a mesitylboryl ligand, which converts to a mesitylborylene ligand upon halido abstraction. In an effort to test the efficacy of this reaction in the presence of different steric and electronic influences, Pt^II diphosphine boryl complexes were prepared with both 4-<i>tert</i>-butylphenyl and duryl (2,3,5,6-tetramethylphenyl) groups. Halide abstraction from the 4-<i>tert</i>-butylphenyl complex resulted in a T-shaped cationic boryl complex. However, subjecting the duryl-substituted complexes to the same conditions exclusively results in terminal cationic borylene complexes, a difference we attribute to the greater steric hindrance between the boron-bound bromide and the methyl groups at the 2- and 6-positions of the duryl group. This outcome indicates that the electronic effect of alkylation at the <i>para</i> position is not a factor for this borylene formation reaction

Short Survey of the Chemical Reduction Behavior of the Base-Stabilized Iron Dichloroboryl Complexes [(η⁵‑C₅Me₅)Fe(CO)₂BCl₂(LB)]

Stable boryl radicals are rare and often reactive species, usually requiring steric and/or electronic stabilization for their isolation. In this paper we describe attempts to use a sterically bulky and electron-rich metal fragment as a stabilizing group toward this end, using alternatively a phosphine, an N-heterocyclic carbene, and 3,5-lutidine as additional Lewis basic stabilization. Reduction of these complexes did not provide a stable radical as hoped, leading instead to decomposition or no reaction in the first two cases. For lutidine, an unusual dinuclear bis­(boryl) product was obtained resulting from C–C coupling of the lutidine bases, suggesting the intermediacy of a reactive radical based partially on the lutidine ring. This possibility was explored computationally

Synthesis and Structure of Distanna and Tristanna Ansa Half-Sandwich Complexes of Ruthenium and Nickel

The synthesis and structural characterization of the first tin-bridged ansa half-sandwich complexes via a two-step protocol from Na­[η⁵-C₅H₅Ru­(CO)₂] and in situ generated Na­[η⁵-C₅H₅Ni­(CO)] are presented. Both compounds are characterized by multinuclear NMR spectroscopy and single-crystal diffraction