Treatment of the new methanediide-methanide complex [Dy(SCS)(SCSH)(THF)] (1Dy, SCS = {C(PPh2S)2}2-) with alkali metal alkyls and auxillary ethers produces the bis-methanediide complexes [Dy(SCS)2][Dy(SCS)2(K(DME)2)2] (2Dy), [Dy(SCS)2][Na(DME)3] (3Dy) and [Dy(SCS)2][K(2,2,2-cryptand)] (4Dy). For...

Antimony pentafluoride is a strong Lewis acid and fluoride-ion acceptor that has not previously demonstrated any discreet fluoride-ion donor properties. The first donor-stabilised [SbF 4 ] + cations were prepared from the autoionisation of SbF 5 in the presence of bidentate N-donor ligands 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen) as their [SbF 6 ] À salts. The [SbF 4 (NÀ N)][Sb 2 F 11 ] (NÀ N = bipy, phen) salts were synthesised by the addition of one equivalent of SbF 5 •SO 2 to [SbF 4 (NÀ N)][SbF 6 ] in liquid SO 2. The salts show remarkable stability and were characterised by Raman spectroscopy and multinuclear NMR spectroscopy. The crystal structures of [SbF 4 (phen)][SbF 6 ] • 3CH 3 CN and [SbF 4 (phen)][SbF 6 ] • 2SO 2 were determined, showing distorted octahedral cations. DFT calculations and NBO analyses reveal that significant degree of electron-pair donation from N to Sb stabilizes [SbF 4 ] + with the SbÀ N bond strength being approximately two thirds of that of the SbÀ F bonds in these cations and the cationic charge being primarily ligand-centred.Antimony pentafluoride, SbF 5 , is one of the strongest F À acceptors currently known, forming highly stable [Sb n F 5n + 1 ] À (n = 1-4) anions. Its solutions in anhydrous HF (aHF) are some of the strongest recorded Bronsted superacids. Antimony pentafluoride is also the benchmark for Lewis superacidity, as molecular Lewis acids with fluoride-ion affinities (FIAs) greater than monomeric SbF 5 in the gas phase (calcd. 501 kJ mol À 1 , exptl. 506 � 60 kJ mol À 1 ) are considered Lewis superacids. [1][2][3] The formation of polynuclear anions, however, can drive the already extreme FIA of SbF 5 even higher. [4] Thus, it is unsurprising that, aside from self-association of solid and liquid SbF 5 to form cis-linked SbF 6 octahedra, the ability of SbF 5 to act as a discrete F À donor is hitherto unknown. However, the lighter pnictogen pentafluorides, PF 5 and AsF 5 , have both previously demonstrated the ability to act as F À donors and form [PnF 4 ] + cations (Pn = P and As). [5,6] In fact, the entire series of [PX 4 ] + (X = F, [5] Cl, [7] Br, [8] I [9,10] ) and their arsonium analogues are known. [6,[11][12][13][14][15][16] Conversely, only [NF

Interactions between ketones and SF4 are studied for the simplest ketone, acetone, and the bulky polycyclic 2‐adamantanone. Acetone forms the 1 : 2 adduct SF4 ⋅ [O=C(CH3)2]2, as well as the dimeric 1 : 1 adducts [SF4 ⋅ O=C(CH3)2]2 as identified by low‐temperature Raman spectroscopy and, for the latter, X‐ray crystallography. In both adducts, SF4 acts as a double chalcogen‐bond donor to two keto groups. In contrast 2‐adamantanone does not form an isolable solid adduct with SF4; in the presence of HF, however, it forms SF4 ⋅ O=C10H14O ⋅ HF, which comprises chains with weak S—O and S—FH chalcogen bonds in the crystal structure. Sulfur tetrafluoride in this compound is readily lost at −85 °C, leading to the isolation of C10H14O ⋅ HF at low temperature. Density functional theory (DFT) calculations aid in vibrational assignments and serve to describe the interactions of the keto group with SF4 and HF, as well as interactions between SF4 with HF. It is found that separate and combined CO—HF and CO—SF4 chalcogen bonds do not polarize the C=O group to any significant degree.