The reaction of the {(Et2N)3P═N}3P═NtBu phosphazene base (EtP4) with bis(trifluoromethyl)disulfide, (F3CS)2, selectively affords [EtP4SCF3][SCF3], which arises from formal heterolytic S─S bond cleavage. The phosphazenium salt represents the first structurally characterized SCF3 substituted iminium derivative. Subsequent reaction with methyl halides MeX (X = Br, I) leads to selective substitution of the anionic SCF3 moiety and facilitates isolation of the corresponding [EtP4SCF3]X (X = Br, I) salts. Treatment of [EtP4SCF3][SCF3] with trimethylsilyl halides Me3SiX (X = Cl, Br) affords halogenophosphonium halide salts [({Et2N}3P═N)3PX]X (X = Cl, Br), via removal of the iminium unit at the phosphazene center. All compounds were characterized by multinuclear NMR spectroscopy, single-crystal X-ray diffraction experiments, and elemental analyses. Both SCF3 units are chemically addressable and can be employed in further functionalization. In contrast, no reaction of (F3CS)2 is observed when the iminophosphorane (C4H8N)3P═NtBu is employed under comparable conditions, whereas the phosphanes PMe3 and P(NEt2)3 undergo conversion to the corresponding difluorophosphoranes. These observations underline the exceptional ability of the EtP4 phosphazene base to promote bond activation and to stabilize the resulting reactive SCF3.

Silicon(IV) halides [{(Et3B)anIPr}SiHCl2] (4) and [{(Et3B)anIPr}SiBr3] (5) based on an anionic N-heterocyclic carbene (NHC) ligand (i.e., {(Et3B)anIPr} = (Et3B)C=C(H){N(Dipp)}2C, Dipp = 2,6-iPr2C6H3) are reported as crystalline solids. Compounds 4 and 5 featuring a four-coordinated Si(IV) atom are prepared by reacting [Li{(Et3B)anIPr}] (3) with HSiCl3 and SiBr4, respectively. 4 and 5 are characterized by spectroscopic and X-ray diffraction methods. Density functional theory (DFT) calculations have been performed to elucidate the electronic structures as well as the fluoride ion affinities (FIAs) of 4 and 5. The calculated FIA, a measure of Lewis acidity, of 4 and 5 is about 46 or 55 kJ/mol larger than that of HSiCl3 and SiBr4, respectively.

The C3v‐symmetric framework of triptindane (C3v‐tribenzo[3.3.3]propellane, 1) was equipped with three benzylic monovalent functional groups in a C3‐symmetric orientation. Key reaction was the reduction of 9,10,11‐triptindanetrione (2) with lithium aluminum hydride or sodium borohydride giving the corresponding C3‐symmetric triol 5 in high yield and perfect diastereoselectivity. The diastereoselective reduction of 9,10‐triptindanedione 9 with LiAlH4 was also studied for comparison. Conversion of triol 5 to the respective tribromide 13, trichloride 14, and triiodide 15 and subsequent refunctionalization of 13 to 9,10,11‐triaminotripindane 18 via the corresponding triazide 16 was achieved with preservation of C3‐symmetry in each case. In contrast, the C1‐triazide 17 is formed along with 16 under Lewis‐acid conditions, enabling an access to the C1‐symmetric triamine 19. The increased torsion about the propellane axis of tribromotriptindane 13 was determined by X‐ray crystallography. There is strong evidence that the reduction 2 → 5 occurs by fast intracomplex transfer of three hydrides from the same alanate ion. In turn, attempts to confirm this by use of an equimolar mixture of LiAlH4 and LiAlD4 were nonsupportive; rather, they point to a hitherto unknown fast hydride exchange occurring in etheral alanate solutions.

Here, we report the use of an alkyne‐functionalized amidine, PhC{N(Dipp)}N(Dipp)C≡CSiMe3 (1) (Dipp = 2,6‐iPr2C6H3), to access a range of Ge(IV), Ge(II/IV), Ge(II), and Ge(I) compounds based on an anionic dicarbene (ADC) framework (ADC = PhC{N(Dipp)C}2). The mixed‐valent Ge(II/IV) complex [{(ADC)GeCl3}GeCl2] (4) is obtained by partial reduction of [{(ADC)GeCl3}GeCl4] (3). Treatment of 1 with 3 affords the Ge(IV) chloride [(ADC)GeCl3]2 (5), which can be sequentially reduced with KC8 to give the known Ge(II) and Ge(I) species [(ADC)GeCl]2 (7) and [(ADC)Ge]2 (8), respectively. The 1,4‐digermabenzene‐1,4‐diide (8) is a singlet diradical that cleaves dihydrogen at room temperature to form the Ge(II) hydride [(ADC)GeH]2 (9); under vacuum, 9 regenerates 8. Compound 8 reacts with azobenzene and diphenylacetylene to yield the corresponding [4+2]‐cycloaddition products, [{(ADC)Ge}EPh]2 10 (E = N) and 11 (E = C), respectively. Treatment of 8 with TEMPO (2,2,6,6‐tetramethylpiperidinyloxyl) produces the radical coupling product, the bis(TEMPO‐germylene) [(ADC)Ge{TEMPO}]2 (13). All compounds were characterized by spectroscopic methods, and their molecular structures, including that of 9, unknown previously, were confirmed by single‐crystal X‐ray diffraction.

Herein we report the synthesis and structural characterization of perfluoroalkylated arsoranide salts. Complementary quantum chemical calculations provide initial insights into the stability of the corresponding anions. Treatment of As(CF3)2I and As(C2F5)2X (X = Br, Cl) with the tetraphenylphosphonium halide salts [PPh4]X (X = I, Br, Cl) affords the diorganyl arsoranide salts [PPh4][As(CF3)2I2] and [PPh4][As(C2F5)X2] (X = Br, Cl) in high yields. For the introduction of fluoride ligands, AgF and CsF were employed as fluoride sources. While CsF enables the selective formation of the metal arsoranide salt Cs[As(C2F5)2F2], the reaction with AgF results only in a halide exchange. However, in the presence of [PPh4]Cl, the corresponding arsoranide salts [PPh4][AsR2F2] (R = CF3, C2F5) are obtained. Treatment of As(CF3)I2 and As(C2F5)X2 (X = Br, Cl) with [PPh4]X furnishes monoorganyl arsoranide salts [PPh4][As(CF3)I3] and [PPh4][As(C2F5)X3] (X = Br, Cl).

The geminal methylene-bridged frustrated Lewis pair Bis(2)Ga-CH2-(PBu2)-Bu-t (1, Bis = CH(SiMe3)(2)) was synthesized by reacting Bis(2)GaBr with (LiCH2PBu2)-Bu-t and its behavior toward small molecules was investigated. Unlike its oxygen-bridged analog, Bis(2)Ga-O-(PBu2)-Bu-t, it does not react with hydrogen gas and decomposes under SO2 atmosphere; however, similar 1,2-addition products of 1 with carbon dioxide, carbon disulfide and cis-azobenzene were obtained. Strikingly, the CO2 adduct undergoes a rearrangement at higher temperatures, with an insertion of the CO2 unit into the Ga-CH2 bond, leading to a gallium carboxylate. All compounds were characterized using multinuclear NMR spectroscopy, elemental analysis, and X-ray diffraction measurements.

Accessing the tetrafluoroargentate anion [AgF4]-, a powerful oxidizing agent, with the silver atom in the formal oxidation state +III, so far required the handling of elemental fluorine and anhydrous HF. Herein, we report a simple and safe method for generating tetrafluoroargentate salts on a preparative scale. Adding tetraalkylammonium halide salts, [NR4]X, or fluortetraphenylphosphorane, FPPh4 to silver difluoride in acetonitrile leads to the formation of the corresponding tetrafluoroargentate salt, [NR4][AgF4], or [PPh4][AgF4] and silver halide AgX via disproportionation. The reaction was monitored employing 19F and 109Ag NMR spectroscopy. In the single-crystal X-ray structure analysis, the expected square planar arrangement of the silver atom is observed, confirming the d8 configuration of the silver ion in the formal oxidation state +III. The fluorinating properties were demonstrated through the oxidation of bis(4-nitrophenyl)disulfide (aryl-S-S-aryl, with aryl = 4-NO2C6H4). The tetrafluoroargentate salt enables the oxidation of sulfur(I) to sulfur(VI), resulting in the formation of aryl-SF5. In strong contrast, treating the disulfide with AgF2 only results in the oxidation to the sulfur(IV) derivative, aryl-SF3, under the same conditions.

Herein we report the syntheses and characterization of bis(pentafluoroethyl)arsinous acid and its conjugate base, bis(pentafluoroethyl)arsinite. Controlled hydrolysis of (diethylamino)bis(pentafluoroethyl)arsane affords the corresponding diethylammonium-arsinite salt [NH2Et2][As(C2F5)2O]. The coordination behavior of the arsinite anion was investigated by reaction of the salt with [TiCp2Cl2] and [Ni(dppp)Cl2], yielding the monosubstituted complexes [TiCp2Cl{OAs(C2F5)2}] and [Ni(dppp)Cl{OAs(C2F5)2}], respectively. Attempts to protonate the arsinite ion by treatment with gaseous HBr did not yield the desired arsinous acid, but resulted in the formation of bromobis(pentafluoroethyl)arsane. However, treatment of the amino arsane with para-toluenesulfonic acid led to the formation of the arsinous acid, which was isolated in 80% yield as a liquid at room temperature. Single crystals of the arsinous acid were grown by in situ crystallization techniques and the molecular structures were determined by single-crystal X-ray diffraction. Quantum-chemical calculations were performed to evaluate equilibria involving arsinous acids.

The oxygen-bridged frustrated Lewis pair (FLP) Bis2Ga-O-PtBu2 (Bis = CH(SiMe3)2; GaOP) is capable of activating and further transforming multiple nitrogen-containing substrates. Remarkably, the reaction with pyridazine leads to an instantaneous, atom-economical ring-contraction at ambient temperature, producing the GaOP·3-hydro-2-imino-pyrrole adduct. Further rearrangement to the GaOP·2-amino-pyrrole adduct occurs due to an imine-enamine tautomerism. Heating this mixture to 70 °C yields the GaOP·5-hydro-2-imino-pyrrole adduct via a 1,3-hydrogen shift. Using phthalazine instead results in the formation of a stable 1,2-addition product across the N-C bond, whereas a subsequent ring-contraction is thermally inducible, yielding the GaOP·9-hydro-2-imino-isoindole adduct. For cis-azobenzene, a 1,2-addition to both nitrogen atoms is observed, while tests for 1,2,4,5-tetrazine derivatives and compounds with N-N single bonds, including hydrazines, show different types of decomposition. Strikingly, ring-opening of the three-membered, N-containing ring in p-tosylaziridine is demonstrated, where by a six-membered ring is formed, as it is the case for the capture of N-sulfinylaniline.

The "soft" pyridine stabilized FLP tBu2In(py)CH2PtBu2 (1·py) was reacted with SO2, PhNCO, PhNSO, azobenzene, pyridazine, 1,2,4,5-tetrazine, tosylaziridine, and hydrazine, respectively. The reactivity can be roughly classified into three types of FLP activation. (a) Typical FLP-type reactivity is observed for the reaction with azobenzene and tosylaziridine, with the formation of 1,2-addition or ring-opening products, respectively. (b) "Soft" FLP-type reactivity occurs toward substrates containing multiple sites for FLP attack-in this case 1·py prefers coordination to the "softer" binding site, resulting in the formation of "soft" isomers of possible FLP adducts, as was demonstrated for PhNCO and PhNSO. (c) An unexpected reactivity results that can be described as a "masked" In/C-FLP; when 1·py was reacted with SO2, an insertion dimer formed, with the methylene bridge connected to the sulfur atom; the reaction of 1·py with hydrazine afforded a four-membered hydrazide heterocycle, under loss of the methylene bridge as MePtBu2, instead of the reaction with the PtBu2 fragment, pyridine, or excess hydrazine. The products were characterized by a variety of NMR spectroscopy methods supported by X-ray crystallography as well as quantum-chemical calculations for insights into the thermodynamics and selectivity of product formation.

Carbonyl olefination reactions have become essential to organic chemistry since Wittig's report on the first reaction of this kind using a phosphorus ylide. While the reaction mechanism of the Wittig olefination is well understood the same cannot be said about the related silicon analogue, the Peterson olefination. Both an open chain, betaine like intermediate and a cyclic 1,2-oxasiletanide intermediate have been discussed since Peterson's original publication, with little evidence for the cyclic intermediates. Herein we present the synthesis and characterization of several stable cyclic Peterson olefination intermediates synthesized via the reaction of an α-silyl carbanion with various ketones. The α-silyl carbanion is stabilized by three pentafluoroethyl groups at the silicon atom. Furthermore, it bears a carbanion stabilizing phenyl group α to the carbanion.

Mono-, bis-, and tris(pentafluoroethyl)plumbanes of the type Pb(C2F5)nAr4- n (Ar = Ph, Tol, Ani; n = 1-3) are easily accessible by treatment of the corresponding arylchloroplumbanes with LiC2F5. The subsequent treatment with HCl furnishes chloro(pentafluoroethyl)plumbanes. The synthesis of the tris(pentafluoroethyl)plumbate(II) anion is facilitated by treatment of Pb(C2F5)3Cl with PPh3. In addition, formation of Pb(C2F5)4 is achieved starting from Pb(OAc)4 and is fully characterized by multinuclear NMR spectroscopy and by single crystal x-ray diffraction of the 1,10-phenanthroline adduct.

In this contribution, we report the synthesis of the diphosphane P2(C2F5)4 and cyclotetraphosphane (PC2F5)4 from the corresponding bromophosphanes P(C2F5)xBr3- x (x = 1, 2). The molecular structure of the cyclotetraphosphane was determined by x-ray diffraction analysis. Subsequent reaction of P2(C2F5)4 with trimethylphosphane (PMe3) afforded the phosphanyl-functionalized phosphorus ylide (Wittig reagent) Me3P = C(CF3)P(C2F5)F, whereas treatment of (PC2F5)4 with PMe3 yielded the base-stabilized phosphinidene Me3P = P(C2F5). The newly obtained species were characterized by multinuclear NMR spectroscopy, and the molecular structures were determined by x-ray diffraction analysis. Me3P = C(CF3)P(C2F5)F as well as Me3P = P(C2F5) represent unique structural motifs that have not been observed within their respective substance class, underlining the remarkable versatility of perfluoroalkyl substituents.

Sulphur-bridged frustrated Lewis pairs (FLPs) of the type Bis2E-S-PtBu2 (ESP; E = Al, Ga) were synthesised in analogy to their oxygen-bridged E-O-P analogues (EOP). An exchange reaction between AlSP and GaOP affords selectively and in accordance with the concept of hard and soft acids and bases (HSAB) the inverted systems AlOP and GaSP. Reactivity studies towards small molecules, such as CO2, CS2, SO2, N2O, and propylene sulphide, revealed differences in adduct formations. The adducts EXP·CX2 and EXP·SO2 (X = O, S) consist of five-membered heterocylces. The oxidation products EXP·X are four-membered rings; they result from the reaction of the EXP with N2O and/or propylene sulfide (under loss of propene), except the reaction of AlSP with propylene sulfide that forms a six-membered ring with the whole substrate molecule. The FLP GaSP is exceptional because the formation of its CO2 adduct is temperature-dependent, confirmed by variable-temperature NMR studies, and its adduct GaSP·CS2 has two structural isomers. All CS2 adducts impress with different colours in solution.

Extremely sterically demanding bis(bis(trimethylsilyl)methyl)‐substituted aluminum and gallium compounds are particularly suitable for applications in frustrated Lewis pair (FLP) chemistry. A selective exchange reaction between Bis 2 GaBr (Bis = CH(SiMe 3 ) 2 ) and Bis 2 AlH affords the previously inaccessible Bis 2 GaH, a monomeric gallium hydride, in solution, as confirmed by diffusion ordered spectroscopy NMR, IR spectroscopy, quantum chemical calculations, and—indirectly—by hydrogallation of phenylacetylene. A simple one‐pot route enables access to Bis 2 EOP t Bu 2 FLPs (E = Al, Ga) via formal HBr adducts and subsequent deprotonation with KHMDS. As predicted for Bis 2 GaOP t Bu 2 , H 2 activation is favored, although it proceeds slowly and irreversibly. Surprisingly, variable‐temperature NMR studies unveil a dynamic equilibrium between the H 2 adduct Bis 2 Ga(H)OP(H) t Bu 2 and the free gallium hydride and phosphine oxide, shedding new light on reversible hydrogen activation in main‐group FLP systems.

ABSTRACT In this contribution, we report the synthesis of the diphosphane P 2 (C 2 F 5 ) 4 and cyclotetraphosphane (PC 2 F 5 ) 4 from the corresponding bromophosphanes P(C 2 F 5 ) x Br 3− x ( x = 1, 2). The molecular structure of the cyclotetraphosphane was determined by x‐ray diffraction analysis. Subsequent reaction of P 2 (C 2 F 5 ) 4 with trimethylphosphane (PMe 3 ) afforded the phosphanyl‐functionalized phosphorus ylide (Wittig reagent) Me 3 P = C(CF 3 )P(C 2 F 5 )F, whereas treatment of (PC 2 F 5 ) 4 with PMe 3 yielded the base‐stabilized phosphinidene Me 3 P = P(C 2 F 5 ). The newly obtained species were characterized by multinuclear NMR spectroscopy, and the molecular structures were determined by x‐ray diffraction analysis. Me 3 P = C(CF 3 )P(C 2 F 5 )F as well as Me 3 P = P(C 2 F 5 ) represent unique structural motifs that have not been observed within their respective substance class, underlining the remarkable versatility of perfluoroalkyl substituents.

In contrast to the vast majority of known frustrated Lewis pair (FLP) systems, which are based on “hard” (hard–soft acid–base, HSAB) boron‐based compounds, this work is on systems containing the “soft” indium Lewis acid functions. The geminal intramolecular indium FLP t Bu 2 InCH 2 P t Bu 2 ( 1 ) was prepared from t Bu 2 InCl and LiCH 2 P t Bu 2 , and its pyridine adduct t Bu 2 In(py)CH 2 P t Bu 2 ( 4 ) was prepared from t Bu 2 InCl(py) and LiCH 2 P t Bu 2 . Both systems are unreactive toward H 2 but show FLP‐typical reactivity toward CO 2 and CS 2 . The cyclic CO 2 and CS 2 adducts of 1 are stable at room temperature, and the CO 2 in the adduct can be replaced by CS 2 , showing that the CO 2 adduct formation is reversible. The catalytic activity of 4 toward CO 2 reduction with pinacolborane to MeOBPin was tested. While 4 shows decent turnover numbers, the turnover frequencies (TOFs) are low due to a long incubation period after the first reduction step. The formaldehyde‐adduct of FLP 1 proved to be an efficient catalyst, reaching TOFs of up to 41.3 h –1 , thus surpassing a previous FLP‐held record of 21 h –1 using pinacolborane as a reducing agent.

The versatile reactivity of the geminal oxygen-bridged frustrated Lewis pair (FLP) Bis(2)Ga-O-PtBu2 (Bis = CH(SiMe3)(2); GaOP) is presented towards a series of CvO double bonds, strained oxygen-containing rings, alkynes plus alkenes and a C-Cl bond. By adding benzaldehyde, cyclopentanone (CP), gamma-butyrolactone (GBL) or ethylene carbonate (EC), classical 1,2-adducts are formed. The reversibility of the GaOP EC adduct stands out, enabling a splitting of EC after several days or when heated to 70 degrees C, resulting in FLP adducts of CO2 and ethylene oxide (EO). The latter consists of a six-membered ring and is obtained via a ring-opening reaction, as verified by a further reaction involving the similar propylene oxide (PO). The GaOP GBL adduct is further converted, with two adduct molecules combining into a 2: 1 FLP adduct in a Claisen-type addition and ring-opening. Tests towards various acetylene containing species revealed that the ratio of deprotonation to ring-closure product can be adjusted. While PhCuCH is almost exclusively bound as the deprotonation product, for Me3SiCuCH, the ring-closure product also forms. In the reaction with benzyl chloride, Bis(2)(Cl)Ga-O-P(Bn)tBu2 is formed by a C-Cl bond activation.

ABSTRACT The reaction of the {(Et 2 N) 3 P═N} 3 P═N t Bu phosphazene base (EtP 4 ) with bis(trifluoromethyl)disulfide, (F 3 CS) 2 , selectively affords [EtP 4 SCF 3 ][SCF 3 ], which arises from formal heterolytic S─S bond cleavage. The phosphazenium salt represents the first structurally characterized SCF 3 substituted iminium derivative. Subsequent reaction with methyl halides MeX (X = Br, I) leads to selective substitution of the anionic SCF 3 moiety and facilitates isolation of the corresponding [EtP 4 SCF 3 ]X (X = Br, I) salts. Treatment of [EtP 4 SCF 3 ][SCF 3 ] with trimethylsilyl halides Me 3 SiX (X = Cl, Br) affords halogenophosphonium halide salts [({Et 2 N} 3 P═N) 3 PX]X (X = Cl, Br), via removal of the iminium unit at the phosphazene center. All compounds were characterized by multinuclear NMR spectroscopy, single‐crystal X‐ray diffraction experiments, and elemental analyses. Both SCF 3 units are chemically addressable and can be employed in further functionalization. In contrast, no reaction of (F 3 CS) 2 is observed when the iminophosphorane (C 4 H 8 N) 3 P═N t Bu is employed under comparable conditions, whereas the phosphanes PMe 3 and P(NEt 2 ) 3 undergo conversion to the corresponding difluorophosphoranes. These observations underline the exceptional ability of the EtP 4 phosphazene base to promote bond activation and to stabilize the resulting reactive SCF 3 .