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The complexes Ag(L)n[WCA] (L=P4S3, P4Se3, As4S3, and As4S4; [WCA]=[Al(ORF)4]− and [F{Al(ORF)3}2]−; RF=C(CF3)3; WCA=weakly coordinating anion) were tested for their performance as ligand‐transfer reagents to transfer the poorly soluble nortricyclane cages P4S3, P4Se3, and As4S3 as well as realgar As4S4 to different transition‐metal fragments. As4S4 and As4S3 with the poorest solubility did not yield complexes. However, the more soluble silver‐coordinated P4S3 and P4Se3 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−P4S3][Al(ORF)4] (1 a), [Fp−P4S3][F(Al(ORF)3)2] (1 b), and [Fp−P4Se3][Al(ORF)4] (2). Reactions with P4S3 also yielded [FpPPh3−P4S3][Al(ORF)4] (3), a complex with the more electron‐rich monophosphine‐substituted Fp+ analogue [FpPPh3]+ ([CpFe(PPh3)(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/FpPPh3 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 P4E3‐cage HOMO (e symmetry) to the metal acceptor fragment. [ABSTRACT FROM AUTHOR]

The complexes Ag(L)n[WCA] (L=P4S3, P4Se3, As4S3, and As4S4; [WCA]=[Al(ORF)4]− and [F{Al(ORF)3}2]−; RF=C(CF3)3; WCA=weakly coordinating anion) were tested for their performance as ligand‐transfer reagents to transfer the poorly soluble nortricyclane cages P4S3, P4Se3, and As4S3 as well as realgar As4S4 to different transition‐metal fragments. As4S4 and As4S3 with the poorest solubility did not yield complexes. However, the more soluble silver‐coordinated P4S3 and P4Se3 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−P4S3][Al(ORF)4] (1 a), [Fp−P4S3][F(Al(ORF)3)2] (1 b), and [Fp−P4Se3][Al(ORF)4] (2). Reactions with P4S3 also yielded [FpPPh3−P4S3][Al(ORF)4] (3), a complex with the more electron‐rich monophosphine‐substituted Fp+ analogue [FpPPh3]+ ([CpFe(PPh3)(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/FpPPh3 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 P4E3‐cage HOMO (e symmetry) to the metal acceptor fragment. [ABSTRACT FROM AUTHOR]

Upon coordinating P4 to electron poor cyclopentadienyl‐iron cations, the average P−P bond distances shrink and the respective P4 breathing mode in the Raman spectra (600 cm−1, P4, free) is blueshifted by >40 cm−1 in [CpFe(CO)(L)(η1‐P4)]+ cations (L=CO or PPh3). 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 P4. [ABSTRACT FROM AUTHOR]

Upon coordinating P4 to electron poor cyclopentadienyl‐iron cations, the average P−P bond distances shrink and the respective P4 breathing mode in the Raman spectra (600 cm−1, P4, free) is blueshifted by >40 cm−1 in [CpFe(CO)(L)(η1‐P4)]+ cations (L=CO or PPh3). 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 P4. [ABSTRACT FROM AUTHOR]

The synthesis of mixed arsenic phosphorus cations was investigated on theoretical and experimental grounds by replacing P4 with AsP3 in the known syntheses of [P4NO]+ and [P9]+. Calculations of [AsP3NO]+ and [AsP8]+ showed that 1‐[AsP3NO]+ and 3‐[AsP8]+ should be the most stable isomers. However, 2‐[AsP3NO]+ was prepared by reacting [NO]+[Al(ORF)4]– (RF = C(CF3)3) with AsP3 with a regioselectivity of 45:1. The kinetic control of this reaction was proven by calculation of the complete reaction mechanism. Examination of the formation energetics of the [AsxP4–xNO]+ (x = 0, 1, 4) and [AsxP9‐x]+ (x = 0, 1, 9) cations at the CCSD(T)/complete basis set limit level showed that for [AsxP4–xNO]+ (x = 0, 1, 4), the replacement of phosphorus by arsenic leads to more exergonic formation energetics. For the [AsxP9‐x]+ clusters (x = 0, 1, 9), the reaction to [AsP8]+ is slightly more exergonic compared to the synthesis of [P9]+. The calculation of the reaction to the homopolyatomic arsenic cation [As9]+ suggested that this reaction will at least be very difficult. Attempts to prepare [AsxP9‐x]+ from AsP3 as well as [Asx]+ from gray arsenic led to the formation of [AsP3NO]+, [P4NO]+, [P9]+ and P4 in case of [AsxP9‐x]+ and decomposition products (e.g. novel As(ORF)3) for [Asx]+. [ABSTRACT FROM AUTHOR]

By reacting P4Se3 and As4S3 with Ag[Al(ORF)4] {–RF = –C(CF3)3 or –hfip [= –C(H)(CF3)2]} in suitable solvents, Ag(P4Se3)[Al(Ohfip)4] (1), Ag(P4Se3)2[Al(ORF)4] (2), Ag(P4Se3)3[Al(ORF)4] (3), Ag2(As4S3)3[Al(ORF)4]2 (4) and Ag(As4S3)2[Al(ORF)4] (5) were synthesized and characterized by SC‐XRD, Mass spectrometry, Raman spectroscopy as well as solution NMR spectroscopy. When using stronger coordinating anions, only P4Se3 forms an isolable complex yielding 1 featuring a [Ag2(P4Se3)2]2+ core capped by anions acting as the first example of P4Se3 coordinating through selenium atoms. Upon using the weakly coordinating anion [Al{OC(CF3)3}4]–, the dimeric complexes 2 and 4 are accessible in dichloromethane or ortho‐difluorobenzene (o‐dfb), respectively. Complex 2 shows isolated [Ag2(P4Se3)4(CH2Cl2)2]2+ dications with a [Ag2(P4Se3)2]2+ core similar to 1. Complex 4 shows isolated [Ag2(As4S3)3]2+ dications featuring a weak argentophilic contact. All of these complexes include solvent molecules or anions in the coordination sphere of the metal. When switching to the polar yet non‐coordinating solvent SO2, the coordination spheres are filled with additional ligands and compounds 3 and 5 form. Complex 3 shows condensed [Ag(P4Se3)3]+ units yielding a one dimensional chain and represents the first homoleptic metal(P4Se3) complex. Complex 5 shows a similar paddle wheel structure as in 4 with interconnecting As4S3 ligands and is the first known example of a homoleptic metal(As4S3) complex. To be or not to be coordinated, that is the question investigated by the study of the coordination behavior of the weakly basic cage molecules P4Se3 and As4S3. Using suitable Ag[WCA] salts and the polar yet non‐coordinating solvent SO2 made it possible to characterize the homoleptic complexes of these ligands, whereas stronger coordinating anions or solvents such as CH2Cl2 and ortho‐difluorobenzene yield dimeric structures displaying new coordination modes. [ABSTRACT FROM AUTHOR]

By reacting P4Se3 and As4S3 with Ag[Al(ORF)4] {–RF = –C(CF3)3 or –hfip [= –C(H)(CF3)2]} in suitable solvents, Ag(P4Se3)[Al(Ohfip)4] (1), Ag(P4Se3)2[Al(ORF)4] (2), Ag(P4Se3)3[Al(ORF)4] (3), Ag2(As4S3)3[Al(ORF)4]2 (4) and Ag(As4S3)2[Al(ORF)4] (5) were synthesized and characterized by SC‐XRD, Mass spectrometry, Raman spectroscopy as well as solution NMR spectroscopy. When using stronger coordinating anions, only P4Se3 forms an isolable complex yielding 1 featuring a [Ag2(P4Se3)2]2+ core capped by anions acting as the first example of P4Se3 coordinating through selenium atoms. Upon using the weakly coordinating anion [Al{OC(CF3)3}4]–, the dimeric complexes 2 and 4 are accessible in dichloromethane or ortho‐difluorobenzene (o‐dfb), respectively. Complex 2 shows isolated [Ag2(P4Se3)4(CH2Cl2)2]2+ dications with a [Ag2(P4Se3)2]2+ core similar to 1. Complex 4 shows isolated [Ag2(As4S3)3]2+ dications featuring a weak argentophilic contact. All of these complexes include solvent molecules or anions in the coordination sphere of the metal. When switching to the polar yet non‐coordinating solvent SO2, the coordination spheres are filled with additional ligands and compounds 3 and 5 form. Complex 3 shows condensed [Ag(P4Se3)3]+ units yielding a one dimensional chain and represents the first homoleptic metal(P4Se3) complex. Complex 5 shows a similar paddle wheel structure as in 4 with interconnecting As4S3 ligands and is the first known example of a homoleptic metal(As4S3) complex. To be or not to be coordinated, that is the question investigated by the study of the coordination behavior of the weakly basic cage molecules P4Se3 and As4S3. Using suitable Ag[WCA] salts and the polar yet non‐coordinating solvent SO2 made it possible to characterize the homoleptic complexes of these ligands, whereas stronger coordinating anions or solvents such as CH2Cl2 and ortho‐difluorobenzene yield dimeric structures displaying new coordination modes. [ABSTRACT FROM AUTHOR]

Upon reacting SeCl4 with Me3Si–F–Al(ORF)3, the selenonium salt SeMeCl2[al‐f‐al] (1) {[al‐f‐al]– = [F[Al(OC(CF3)3)3]2]–} was obtained and characterized by NMR, IR, and Raman spectroscopy as well as single crystal XRD experiments. Despite the [SeX3]+ (X = F, Cl, Br, I) and [SeR3]+ salts (R = aliphatic organic residue) being well known and thoroughly studied, the mixed cations are scarce. The only previous example of a salt with the [SeMeCl2]+ cation is SeMeCl2[SbCl6], which was never structurally characterized and is unstable in solution over hours. Only 1H‐NMR studies and IR spectra of this compound are known. The unexpected use of Me3Si–F–Al(ORF)3 as a methylating agent was investigated via DFT calculations and NMR experiments of the reaction solution. The reaction of SeCl3[al‐f‐al] with Me3Si‐Cl at room temperature in CH2Cl2 proved to yield the same product with Me3Si–Cl acting as a methylating agent. [ABSTRACT FROM AUTHOR]

Upon reacting SeCl4 with Me3Si–F–Al(ORF)3, the selenonium salt SeMeCl2[al‐f‐al] (1) {[al‐f‐al]– = [F[Al(OC(CF3)3)3]2]–} was obtained and characterized by NMR, IR, and Raman spectroscopy as well as single crystal XRD experiments. Despite the [SeX3]+ (X = F, Cl, Br, I) and [SeR3]+ salts (R = aliphatic organic residue) being well known and thoroughly studied, the mixed cations are scarce. The only previous example of a salt with the [SeMeCl2]+ cation is SeMeCl2[SbCl6], which was never structurally characterized and is unstable in solution over hours. Only 1H‐NMR studies and IR spectra of this compound are known. The unexpected use of Me3Si–F–Al(ORF)3 as a methylating agent was investigated via DFT calculations and NMR experiments of the reaction solution. The reaction of SeCl3[al‐f‐al] with Me3Si‐Cl at room temperature in CH2Cl2 proved to yield the same product with Me3Si–Cl acting as a methylating agent. [ABSTRACT FROM AUTHOR]

By reacting As4S4 (realgar) with Ag[Al(ORF)4] [RF = C(CF3)3] in SO2 or ortho‐difluorobenzene (o‐dfb) at room temperature, the compounds Ag(As4S4)(SO2)2[Al(ORF)4] (1) and Ag3(As4S4)4(o‐dfb)[Al(ORF)4]3 (2) were obtained and characterized by single‐crystal X‐ray structure determinations, Raman spectroscopy, as well as solution NMR spectroscopy and mass spectrometry. Compound 1 aggregates to form a one‐dimensional polymer including SO2 ligands binding to the metal cation. Compound 2 forms a two‐dimensional polymer displaying an unprecedented coordination mode of the ligand through one of the arsenic atoms. As a side reaction in o‐dfb, small amounts of the oxidation product As3S4[Al(ORF)4] (3) form. This result indicates that coordination to arsenic is energetically near to the degradation and oxidation of the cluster. Experiments, as well as orienting DFT calculations suggest that the As4S4 cage is an inferior ligand, compared to the nortricyclane cages P4E3 (E = S, Se) and As4S3. Electronegativity arguments, as well as population analyses with three independent methods suggest that the sulfur atoms in realgar always bear a negative partial charge. Thus, if the coordination of the ligand is a charge‐controlled reaction, coordination of realgar should proceed through the sulfur atoms. However, the close energetic proximity of HOMO and HOMO–1 indicates that frontier orbital control could either proceed through an η2(S; S), or η1(As) coordination, as observed in one case. [ABSTRACT FROM AUTHOR]

By reacting As4S4 (realgar) with Ag[Al(ORF)4] [RF = C(CF3)3] in SO2 or ortho‐difluorobenzene (o‐dfb) at room temperature, the compounds Ag(As4S4)(SO2)2[Al(ORF)4] (1) and Ag3(As4S4)4(o‐dfb)[Al(ORF)4]3 (2) were obtained and characterized by single‐crystal X‐ray structure determinations, Raman spectroscopy, as well as solution NMR spectroscopy and mass spectrometry. Compound 1 aggregates to form a one‐dimensional polymer including SO2 ligands binding to the metal cation. Compound 2 forms a two‐dimensional polymer displaying an unprecedented coordination mode of the ligand through one of the arsenic atoms. As a side reaction in o‐dfb, small amounts of the oxidation product As3S4[Al(ORF)4] (3) form. This result indicates that coordination to arsenic is energetically near to the degradation and oxidation of the cluster. Experiments, as well as orienting DFT calculations suggest that the As4S4 cage is an inferior ligand, compared to the nortricyclane cages P4E3 (E = S, Se) and As4S3. Electronegativity arguments, as well as population analyses with three independent methods suggest that the sulfur atoms in realgar always bear a negative partial charge. Thus, if the coordination of the ligand is a charge‐controlled reaction, coordination of realgar should proceed through the sulfur atoms. However, the close energetic proximity of HOMO and HOMO–1 indicates that frontier orbital control could either proceed through an η2(S; S), or η1(As) coordination, as observed in one case. [ABSTRACT FROM AUTHOR]

The recently published purely metallo-organic NiI salt [Ni(cod)2][Al(ORF)4] (1, cod=1,5-cyclooctadiene, RF= C(CF3)3) provides a starting point for a new synthesis strategy leading to NiI 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(ORF)4] (2, dppp=1,3-bis(diphenylphosphino) propane), [Ni(dppe)2][Al(ORF)4] (3, dppe=1,3-bis(diphenyl- phosphino)ethane), three-coordinate [Ni(PPh3)3] [Al(ORF)4] (4) and a remarkable two-coordinate NiI phosphine complex [Ni(PtBu3)2][Al(ORF)4] (5) were characterised by single crystal X-ray structure analysis. EPR studies were performed, confirming a nickel d9 -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 NiI compounds between 0.7 and 1.7 V versus Fc/Fc+. Screening reactions with O2 and CO gave first insights on the reaction behaviour of the NiI phosphine complexes towards small molecules with formation of mixed phosphine- CO-NiI complexes and oxidation processes yielding new NiI and/or NiII derivatives. Moreover, 4 reacted with CH2Cl2 at RT to give a dimeric NiII ylide complex (4c). As CH2Cl2 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. [ABSTRACT FROM AUTHOR]

To provide a better understanding of the recently published pure metalorganic NiI species, [Ni(cod)2][Al(ORF)4] (1) [cod = 1,5- cyclooctadiene, RF = C(CF3)3], further characterizations were performed and analyzed. Thus, the solvation of 1 in THF was examined by EPR, surprisingly disclosing the initiation of a disproportionation reaction to [NiII(THF)6][Al(ORF)4]2 (3) and Ni0. Further studies con- cerning the ability of 1 to activate small molecules exhibit the formation of a remarkable [Ni3S2(cod)3]2+ cluster (5) in an oxidation reaction with S8, while EPR measurements of the resulting product in a reaction with oxygen indicate a possible coordination of O2. Single crystal X-ray structures as well as spectroscopic analyses of 3 and 5 are described. [ABSTRACT FROM AUTHOR]

The straightforward synthesis of the cationic, purely organometallic NiI salt [Ni(cod)2]+[Al(ORF)4]- was realized through a reaction between [Ni(cod)2] and Ag[Al(ORF)4] (cod=1,5-cyclooctadiene). Crystal-structure analysis and EPR, XANES, and cyclic voltammetry studies confirmed the presence of a homoleptic NiI olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic NiI complexes. The straightforward synthesis of the cationic, purely organometallic NiI salt [Ni(cod)2]+[Al(ORF)4]- was realized through a reaction between [Ni(cod)2] and Ag[Al(ORF)4] (cod=1,5-cyclooctadiene). Crystal-structure analysis and EPR, XANES, and cyclic voltammetry studies confirmed the presence of a homoleptic NiI olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic NiI complexes. [ABSTRACT FROM AUTHOR]

Highlights from the article: Umpolung of the P4-Bonding Situation in [CpFe(CO)(L)( 1-P4)]+ Cations (L=CO or PPh3) B A low barrier to the exchange b of metalated and non-metalated phosphorus atoms is observed in white phosphorus complexes of electron poor cyclopentadienyl iron cations. Analysis of the bonding present in these systems identifies a formal Umpolung in the Fe-P bond resulting from the electron deficient nature of the iron center.

The synthesis of mixed arsenic phosphorus cations was investigated on theoretical and experimental grounds by replacing P4 with AsP3 in the known syntheses of [P4NO]+ and [P9]+. Calculations of [AsP3NO]+ and [AsP8]+ showed that 1‐[AsP3NO]+ and 3‐[AsP8]+ should be the most stable isomers. However, 2‐[AsP3NO]+ was prepared by reacting [NO]+[Al(ORF)4]– (RF = C(CF3)3) with AsP3 with a regioselectivity of 45:1. The kinetic control of this reaction was proven by calculation of the complete reaction mechanism. Examination of the formation energetics of the [AsxP4–xNO]+ (x = 0, 1, 4) and [AsxP9‐x]+ (x = 0, 1, 9) cations at the CCSD(T)/complete basis set limit level showed that for [AsxP4–xNO]+ (x = 0, 1, 4), the replacement of phosphorus by arsenic leads to more exergonic formation energetics. For the [AsxP9‐x]+ clusters (x = 0, 1, 9), the reaction to [AsP8]+ is slightly more exergonic compared to the synthesis of [P9]+. The calculation of the reaction to the homopolyatomic arsenic cation [As9]+ suggested that this reaction will at least be very difficult. Attempts to prepare [AsxP9‐x]+ from AsP3 as well as [Asx]+ from gray arsenic led to the formation of [AsP3NO]+, [P4NO]+, [P9]+ and P4 in case of [AsxP9‐x]+ and decomposition products (e.g. novel As(ORF)3) for [Asx]+. [ABSTRACT FROM AUTHOR]

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.)

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 .