Anindya K. Swarnakar

Application of the donor-acceptor concept to intercept low oxidation state group 14 element hydrides using a Wittig reagent as a Lewis base.

This article outlines our attempts to stabilize the Group 14 element dihydrides, GeH2 and SnH2, using commonly employed phosphine and pyridine donors; in each case, elemental Ge and Sn extrusion was noted. However, when these phosphorus and nitrogen donors were replaced with the ylidic Wittig ligand Ph3P═CMe2, stable inorganic methylene complexes (EH2) were obtained, demonstrating the utility of this under-explored ligand class in advancing main group element coordination chemistry.

Encapsulating Inorganic Acetylene, HBNH, Using Flanking Coordinative Interactions

A stable donor-acceptor coordination complex of the elusive parent inorganic iminoborane HBNH (a structural analogue of acetylene) is reported. This species was generated via thermally induced N2 elimination/1,2-H migration from a hydrido(azido)borane adduct NHC⋅BH2N3 (NHC=N-heterocyclic carbene) in the presence of a fluorinated triarylborane. The mechanism of this process was also investigated by computational and isotopic labeling studies. This transformation represents a new and potentially modular route to unsaturated inorganic building blocks for advanced material synthesis.

Direct Evaluation of the Quantum Confinement Effect in Single Isolated Ge Nanocrystals

To address the yet open question regarding the nature of quantum confinement in Ge nanocrystals (Ge NCs) we employed scanning tunneling spectroscopy to monitor the electronic structure of individual isolated Ge NCs as a function of their size. The (single-particle) band gaps extracted from the tunneling spectra increase monotonically with decreasing nanocrystal size, irrespective of the capping ligands, manifesting the effect of quantum confinement. Band-gap widening of ∼1 eV with respect to the bulk value was observed for Ge-NCs 3 nm in diameter. The picture emerging from comparison with theoretical calculations and other experimental results is discussed.

Preparation and Structures of Group 12 and 14 Element Halide–Carbene Complexes

The synthesis of a series of N-heterocyclic carbene (NHC) complexes involving zinc, cadmium, and the heavy Group 14 elements germanium, tin, and lead is reported. The direct reaction between the bulky carbene IPr (IPr = (HCNDipp)2C:, Dipp = 2,6-iPr2C6H3) and the Group 14 halide reagents GeCl4 and SnCl4 afforded the 1 : 1 complexes IPr·ECl4 (E = Ge and Sn) in high yield; similarly, ZnI2 interacted with IPr in THF to give the THF-bound complex IPr·ZnI2·THF. CdCl2 underwent divergent chemistry with IPr and the major product isolated was the imidazolium salt [IPrH][IPr·CdCl3], which could be converted into IPr·CdCl2·THF upon treatment with Tl[OTf]. In addition, the stable PbII amide adduct, IPr·PbBr(NHDipp), was prepared. Each of the new carbene–element halide adducts was treated with the hydride sources Li[BH4] and Li[HBEt3] in order to potentially access new element hydride adducts and/or clusters. In most instances scission of the element–carbene bonds transpired, except in the case of IPr·ZnI2·THF, which reacted with two equivalents of Li[BH4] to yield the thermally stable bis(borohydride) zinc complex IPr·Zn(BH4)2.

Oxoborane (RBO) Complexation and Concomitant Electrophilic Bond Activation Processes

Donor-acceptor complexes of the oxoboranes ClB=O and HOB=O were synthesized and each feature short multiply bonded B=O linkages. The retention of high Lewis acidic character within these encapsulated monomeric oxoboranes was manifested by their ability to support C-F and Si-O bond activation/functionalization. The reported ClB=O complexes can be regarded as synthetic surrogates of the [BO]+ cation, an inorganic analogue of CO.

CCDC 1514190: Experimental Crystal Structure Determination

Related Article: Anindya K. Swarnakar, Christian Hering-Junghans, Michael J. Ferguson, Robert McDonald, Eric Rivard|2017|Chemical Science|8|2337|doi:10.1039/C6SC04893E

CCDC 1514195: Experimental Crystal Structure Determination

Related Article: Anindya K. Swarnakar, Christian Hering-Junghans, Michael J. Ferguson, Robert McDonald, Eric Rivard|2017|Chemical Science|8|2337|doi:10.1039/C6SC04893E