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Condensed phase access to the unprecedented tetrahedral cations [EP 3 ] + (E = S, Se, Te) was achieved through the reaction of ECl 3 [WCA] with white phosphorus ([WCA] - = [Al(OR F ) 4 ] - and [F(Al(OR F ) 3 ) 2 ] - ; -R F = -C(CF 3 ) 3 ). Previously, [EP 3 ] + was only known from gas phase MS investigations. By contrast, the reaction of ECl 3 [A] with the known P 3 3- synthon Na[Nb(ODipp) 3 (P 3 )] (enabling AsP 3 synthesis), led to formation of P 4 . The cations [EP 3 ] + were characterized by multinuclear NMR spectroscopy in combination with high-level quantum chemical calculations. Their bonding situation is described with several approaches including Atoms in Molecules and Natural Bond Orbital analysis. The first series of well-soluble salts ECl 3 [WCA] was synthesized and fully characterized as starting materials for the studies on this elusive class of [EP 3 ] + cations. Yet, with high [ECl 3 ] + fluoride ion affinity values between 775 (S), 803 (Se) and 844 (Te) kJ mol -1 , well exceeding typical phosphenium ions, these well-soluble ECl 3 [WCA] salts could be relevant in view of the renewed interest in strong (also cationic) Lewis acids., (This journal is © The Royal Society of Chemistry 2019.)

The complexes Ag(L) n [WCA] (L=P 4 S 3 , P 4 Se 3 , As 4 S 3 , and As 4 S 4 ; [WCA]=[Al(OR F ) 4 ] - and [F{Al(OR F ) 3 } 2 ] - ; R F =C(CF 3 ) 3 ; WCA=weakly coordinating anion) were tested for their performance as ligand-transfer reagents to transfer the poorly soluble nortricyclane cages P 4 S 3 , P 4 Se 3 , and As 4 S 3 as well as realgar As 4 S 4 to different transition-metal fragments. As 4 S 4 and As 4 S 3 with the poorest solubility did not yield complexes. However, the more soluble silver-coordinated P 4 S 3 and P 4 Se 3 cages were transferred to the electron-poor Fp + moiety ([CpFe(CO) 2 ] + ). Thus, reaction of the silver salt in the presence of the ligand with Fp-Br yielded [Fp-P 4 S 3 ][Al(OR F ) 4 ] (1 a), [Fp-P 4 S 3 ][F(Al(OR F ) 3 ) 2 ] (1 b), and [Fp-P 4 Se 3 ][Al(OR F ) 4 ] (2). Reactions with P 4 S 3 also yielded [FpPPh 3 -P 4 S 3 ][Al(OR F ) 4 ] (3), a complex with the more electron-rich monophosphine-substituted Fp + analogue [FpPPh 3 ] + ([CpFe(PPh 3 )(CO)] + ). All complex salts were characterized by single-crystal XRD, NMR, Raman, and IR spectroscopy. Interestingly, they show characteristic blueshifts of the vibrational modes of the cage, as well as structural contractions of the cages upon coordination to the Fp/FpPPh 3 moieties, which oppose the typically observed cage expansions that lead to redshifts in the spectra. Structure, bonding, and thermodynamics were investigated by DFT calculations, which support the observed cage contractions. Its reason is assigned to σ and π donation from the slightly P-P and P-E antibonding P 4 E 3 -cage HOMO (e symmetry) to the metal acceptor fragment., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Upon coordinating P 4 to electron poor cyclopentadienyl-iron cations, the average P-P bond distances shrink and the respective P 4 breathing mode in the Raman spectra (600 cm -1 , P 4, free ) is blueshifted by >40 cm -1 in [CpFe(CO)(L)(η 1 -P 4 )] + cations (L=CO or PPh 3 ). Analysis suggests that this corresponds to an umpolung of the bonding from more phosphidic in the known, electron-rich systems to more phosphonium-like in the reported electron-poor versions. This may open new functionalization pathways for white phosphorus P 4 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

By reaction of the Lewis acid Me 3 Si-F-Al(OR F ) 3 with a series of [PF 6 ] - salts, gaseous PF 5 and Me 3 Si-F are liberated and salts of the anion [F-Al(OR F ) 3 ] - ([f-al] - ; R F = C(CF 3 ) 3 ) can be obtained. By addition of another equivalent of Me 3 Si-F-Al(OR F ) 3 to [f-al] - , gaseous Me 3 Si-F is released and salts of the least coordinating anion [(R F O) 3 Al-F-Al(OR F ) 3 ] - ([al-f-al] - ) are formed. Both procedures work for a series of synthetically useful cations including Ag + , [NO] + , [Ph 3 C] + and in very clean reactions with 5 g batch sizes giving excellent yields typically exceeding 90%. In addition, the synthesis of Me 3 Si-F-Al(OR F ) 3 has been optimized and scaled up to 85 g batches in an one-pot procedure. These anions could previously only be obtained by difficult to control decomposition reactions of [Al(OR F ) 4 ] - or by halide abstraction reactions with Me 3 Si-F-Al(OR F ) 3 , generating relatively large countercations that are unsuited for further use as universal starting materials. Especially [al-f-al] - is of interest for the stabilization of reactive cations, since it is even weaker coordinating than [Al(OR F ) 4 ] - and more stable against strong electrophiles. This bridged anion can be seen as an adduct of [f-al] - and Al(OR F ) 3 . Thus, it is similarly Lewis acidic as BF 3 and eventually reacts with nucleophiles (Nu) from the reaction environment to yield Nu-Al(OR F ) 3 and [f-al] - . This prevents working with [al-f-al] - salts in ethereal or other donor solvents. By contrast, the [f-al] - anion is no longer Lewis acidic and may therefore be used for reactions involving stronger nucleophiles than the [al-f-al] - anion can withstand. Subsequently it may be transformed into the [al-f-al] - salt by simple addition of one equivalent of Me 3 Si-F-Al(OR F ) 3 .

The recently published purely metallo-organic Ni I salt [Ni(cod) 2 ][Al(OR F ) 4 ] (1, cod=1,5-cyclooctadiene, R F =C(CF 3 ) 3 ) provides a starting point for a new synthesis strategy leading to Ni I phosphine complexes, replacing cod ligands by phosphines. Clearly visible colour changes indicate reactions within minutes, while quantum chemical calculations (PBE0-D3(BJ)/def2-TZVPP) approve exergonic reaction enthalpies in all performed ligand exchange reactions. Hence, [Ni(dppp) 2 ][Al(OR F ) 4 ] (2, dppp=1,3-bis(diphenylphosphino)propane), [Ni(dppe) 2 ][Al(OR F ) 4 ] (3, dppe=1,3-bis(diphenyl-phosphino)ethane), three-coordinate [Ni(PPh 3 ) 3 ][Al(OR F ) 4 ] (4) and a remarkable two-coordinate Ni I phosphine complex [Ni(PtBu 3 ) 2 ][Al(OR F ) 4 ] (5) were characterised by single crystal X-ray structure analysis. EPR studies were performed, confirming a nickel d 9 -configuration in complexes 2, 4 and 5. This result is supported by additional magnetization measurements of 4 and 5. Further investigations by cyclic voltammetry indicate relatively high oxidation potentials for these Ni I compounds between 0.7 and 1.7 V versus Fc/Fc + . Screening reactions with O 2 and CO gave first insights on the reaction behaviour of the Ni I phosphine complexes towards small molecules with formation of mixed phosphine-CO-Ni I complexes and oxidation processes yielding new Ni I and/or Ni II derivatives. Moreover, 4 reacted with CH 2 Cl 2 at RT to give a dimeric Ni II ylide complex (4 c). As CH 2 Cl 2 is a rather stable alkyl halide with relatively high C-Cl bond energies, 4 appears to be a suitable reagent for more general C-Cl bond activation reactions., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The straightforward synthesis of the cationic, purely organometallic Ni(I) salt [Ni(cod)2](+)[Al(OR(F))4](-) was realized through a reaction between [Ni(cod)2] and Ag[Al(OR(F))4] (cod = 1,5-cyclooctadiene). Crystal-structure analysis and EPR, XANES, and cyclic voltammetry studies confirmed the presence of a homoleptic Ni(I) olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic Ni(I) complexes., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)