A series of phosphine-diphenylphosphenium donor-acceptor cationic complexes have been synthesized and comprehensively characterized (phosphine = diphenylchlorophosphine, triphenylphosphine, trimethylphosphine, and tricyclohexylphosphine). The complexes involve homoatomic P-P coordinate bonds that are susceptible to ligand exchange reactions highlighting a versatile new synthetic method for P-P bond formation. Phosphenium complexes of 1,2-bis(diphenylphosphino)benzene and 1,2-bis(tert-butylphosphino)benzene undergo unusual rearrangements to give a "segregated" diphosphine-phosphonium cation and a cyclic di(phosphino)phosphonium cation, respectively. The rearrangement products reveal the kinetic stability of the phosphine-phosphenium bonding arrangement.

A combined donor/acceptor approach is presented for the stabilization of the parent germylene, :GeH2.

Palladium-catalysed C(sp 2 )-N cross-coupling (that is, Buchwald-Hartwig amination) is employed widely in synthetic chemistry, including in the pharmaceutical industry, for the synthesis of (hetero)aniline derivatives. However, the cost and relative scarcity of palladium provides motivation for the development of alternative, more Earth-abundant catalysts for such transformations. Here we disclose an operationally simple and air-stable ligand/nickel(II) pre-catalyst that accommodates the broadest combination of C(sp 2 )-N coupling partners reported to date for any single nickel catalyst, without the need for a precious-metal co-catalyst. Key to the unprecedented performance of this pre-catalyst is the application of the new, sterically demanding yet electron-poor bisphosphine PAd-DalPhos. Featured are the first reports of nickel-catalysed room temperature reactions involving challenging primary alkylamine and ammonia reaction partners employing an unprecedented scope of electrophiles, including transformations involving sought-after (hetero)aryl mesylates for which no capable catalyst system is known.

Various low oxidation state (+2) group 14 element amidohydride adducts, IPr⋅EH(BH(3))NHDipp (E=Si or Ge; IPr=[(HCNDipp)(2)C:], Dipp=2,6-iPr(2)C(6)H(3)), were synthesized. Thermolysis of the reported adducts was investigated as a potential route to Si- and Ge-based clusters; however, unexpected transmetallation chemistry occurred to yield the carbene-borane adduct, IPr⋅BH(2)NHDipp. When a solution of IPr⋅BH(2)NHDipp in toluene was heated to 100 °C, a rare C-N bond-activation/ring-expansion reaction involving the bound N-heterocyclic carbene donor (IPr) transpired.

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Adamantyl-end-capped polyynes with chains of 4, 6, 8, 10, 12, 16, and 20 sp-hybridized carbons (C4-C20) have been synthesized and their IR and Raman spectra obtained. On the basis of violations of the mutual-exclusion principle between IR and Raman spectroscopy, spectral evidence demonstrates that these molecules possess a noncentrosymmetric molecular structure in both the solid and solution states. This premise is supported by X-ray crystallographic analysis of C12, which shows a bent, noncentrosymmetric structure in the solid state. Density functional theory (DFT) calculations for adamantyl-end-capped polyynes, in comparison with those for hydrogen-end-capped polyynes, show that the observed violation of mutual exclusion is independent of the end group of the polyyne chain (i.e., adamantyl versus H). The origin of these experimental spectroscopic observations is ascribed to the existence of dynamic contributions to molecular nonlinearity resulting from low-frequency skeletal bending vibrations of the chains and/or the existence of low-energy bent conformations of the polyyne chains, as DFT-optimized structures seem to suggest.

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