Tobias A. Engesser

[P9]+[Al(ORF)4]−, the Salt of a Homopolyatomic Phosphorus Cation†

Positive at last: The first condensed-phase homopolyatomic phosphorus cation [P(9)](+) was prepared using a combination of the oxidant [NO](+) and weakly coordinating anion, [Al{OC(CF(3))(3)}(4)](-). [P(9)](+) consists of two P(5) cages linked by a phosphonium atom to give a D(2d)-symmetric Zintl cluster. NMR (see picture), Raman, and IR spectroscopy, mass spectrometry, and quantum-chemical calculations confirmed the structure.

The Reaction of White Phosphorus with NO+/NO2+[Al(ORF)4]−: The [P4NO]+ Cluster Formed by an Unexpected Nitrosonium Insertion†

Despite decades of intense research into polyphosphorus chemistry, our knowledge of homoleptic polyphosphorus cations is still limited to the results of mass spectrometry and quantum chemical calculations. In general, the diamagnetic cage cations with an odd number of phosphorus atoms are more stable, with P9 , composed of two C2v symmetric P5 cages joined by a common phosphonium atom having special stability. This cage was found in one of the few types of simple inorganic phosphorus cluster cations that are known, that is, [P5R2] + (R = Cl, Br, I, Ph, DippN(Cl)NDipp (Dipp = 2,6-diisopropylphenyl)). Those P5 cages are formed by the formal insertion of carbene-analogous PR2 + fragments into the P P bond of P4 (see Ref. [9, 10] for Reviews on P4 activation). Stable carbenes also interact with P4, leading to compounds including P1 up to P12 moieties, depending on the electronic nature of the carbene. Larger cationic P7 cages were recently prepared, but all preparative approaches to true Pn + ions remained futile. However, we expected that an appropriate one-electron oxidant should be able to oxidize P4 (ionization energy (IE) 9.34 eV) and lead to phosphorus cluster cations Pn . Herein we give an account of the reaction of P4 with the salts [NO] [Al(OC(CF3)3)4] [13] (1; IE NO = 9.26 eV) and [NO2] [Al(OC(CF3)3)4] (2 ; IE NO2 = 9.59 eV. At least 2 was expected to be a strong enough oxidant to yield Pn + cations. The novel salt 2 was synthesized in 94 % yield from NO2[BF4] and Li[Al(OC(CF3)3)4] in SO2 solution with precipitation of insoluble Li[BF4]; it was fully characterized by X-ray diffraction and vibrational and NMR spectroscopy (for details, see the Supporting Information). Unexpectedly, the reactions of 1 and 2 with P4 in CH2Cl2 show an analogous process, regardless of the ratios of phosphorus to oxidant employed (between 3P:1 NOx + and 9P:1 NOx ). They form a red intermediate and yield the same yellow final product ([P4NO] [Al(OC(CF3)3)4] (3 ; Scheme 1). Compound 3 may be viewed as the insertion

In‐Between Complex and Cluster: A 14‐Vertex Cage in [Ag2Se12]2+

Numerous cyclic sulfur and selenium allotropes En (E = S: n = 6–15, 18, 20 etc.; E = Se: n = 6, 7, 8) are known, while hexagonal Te1 remains the only accessible allotrope of tellurium. For Se, the stability of the allotropes increases from Se7< Se6< Se8< Se1. Although being structurally related to crown ethers, only a few examples of chalcogen rings coordinated to a metal ion exist, including [Agn(Se6)] n+ (n = 1, 2), 3] [M(S8)n] + (M = Cu; Ag), [Cu(S12)] , [Cu(S8)(S12)] . All of these cations are partnered with weakly coordinating anions (WCA). Related salts containing almost non-interacting cationic stacks are [Rb(Se8) ]1 [8] and [Rb(Se6)2 ]1. [9] The neutral selenium complexes [PdX2(Se6)] [10] (X = Cl, Br), [(AgI)2Se6], [11] [Re2I2(CO)6(Se7)], [12]

Homoleptic Gold Acetonitrile Complexes with Medium to Very Weakly Coordinating Counterions: Effect on Aurophilicity?

A series of gold acetonitrile complexes [Au(NCMe)2 ]+ [WCA]- with weakly coordinating counterions (WCAs) was synthesized by the reaction of elemental gold and nitrosyl salts [NO]+ [WCA]- in acetonitrile ([WCA]- =[GaCl4 ]- , [B(CF3 )4 ]- , [Al(ORF )4 ]- ; RF =C(CF3 )3 ). In the crystal structures, the [Au(NCMe)2 ]+ units appeared as monomers, dimers, or chains. A clear correlation between the aurophilicity and the coordinating ability of counterions was observed, with more strongly coordinating WCAs leading to stronger aurophilic contacts (distances, C-N stretching frequencies of [Au(NCMe)2 ]+ units). An attempt to prepare [Au(L)2 ]+ units, even with less weakly basic solvents like CH2 Cl2 , led to decomposition of the [Al(ORF )4 ]- anion and formation of [NO(CH2 Cl2 )2 ]+ [F(Al(ORF )3 )2 ]- . All nitrosyl reagents [NO]+ [WCA]- were generated according to an optimized procedure and were thoroughly characterized by Raman and NMR spectroscopy. Moreover, the to date unknown species [NO]+ [B(CF3 )3 CN]- was prepared. Its reaction with gold unexpectedly produced [Au(NCMe)2 ]+ [Au(NCB(CF3 )3 )2 ]- , in which the cyanoborate counterion acts as an anionic ligand itself. Interestingly, the auroborate anion [Au(NCB(CF3 )3 )2 ]- behaves as a weakly coordinating counterion, which becomes evident from the crystallographic data and the vibrational spectral characteristics of the [Au(NCMe)2 ]+ cation in this complex. Ligand exchange in the only room temperature stable salt of this series, [Au(NCMe)2 ]+ [Al(ORF )4 ]- , is facile and, for example, [Au(PPh3 )(NCMe)]+ [Al(ORF )4 ]- can be selectively generated. This reactivity opens the possibility to generate various [AuL1 L2 ]+ [Al(ORF )4 ]- salts through consecutive ligand-exchange reactions that offer access to a huge variety of AuI complexes for gold catalysis.