The cyclostibane R₄Sb₄ (1) (R = 2-(Me₂NCH₂)C₆H₄) was synthesized by reduction of RSbCl₂ with Mg in THF or with Na in liquid NH₃ . The reaction of 1 with [W(CO)₅(THF)] gives the stibinidene complex RSb[W(CO)₅]₂ (2). RSbCl₂ and (RSbCl)₂E [E = O (6), E = S (8)] react with KOH or Na₂S in toluene/water to give the heterocycles (RSbE)_n [E = O, n = 3 (3); E = S, n = 2 (4)]. The chalcogeno-bridged compounds of the type (RSbCl)₂E [E = O (6), E = S (8)] were synthesized by reaction of RSbCl₂ with KOH or Na₂S in toluene/water, but also by reaction of RSbCl₂ with the heterocycles (RSbE)_n. The compounds (RSbI)₂O (7) and (RSbBr)₂S (9) were prepared via halogen-exchange reactions between (RSbCl)₂E and NaI (E = O) or KBr (E = S) or by reactions between RSbI₂ and KOH or RSbBr₂ and Na₂S. The reaction of cyclo-(RSbS)₂ with W(CO)₅(THF) in THF results in trapping of the cis isomer in cyclo-(RSbS)₂[W(CO)₅] (5). The solution behaviour of the compounds was investigated by ¹H and ¹³C NMR spectroscopy. The molecular structures of compounds 1–7 and 9 were determined by single-crystal X-ray diffraction.

Hypervalent antimony(III) halides of the type R₂SbX [X = Cl (1), Br (2), I (3)] and RSbX₂ [X = Cl (4), Br (5), I (6)] [R = 2-(Me₂NCH₂)C₆H₄] have been prepared. Their dynamic solution behavior was investigated by ¹H and ¹³C NMR spectroscopy. The structures of compounds 2–6 were determined by single-crystal X-ray diffraction and the observed trends in the degree of intramolecular coordination of the N atom of the pending CH₂NMe₂ arm are discussed. Compounds 2 and 3 are monomeric and exhibit distorted square-pyramidal (C,N)₂SbX cores. The molecular structure of the adduct R₂SbI·HI (3·HI) indicates the strong coordination of one of the N atoms to antimony. The second pendant arm is twisted away from the metal center, its N atom being protonated and thus converted into an ammonium group. The molecules of 4–6 contain a pseudo-trigonal bipyramidal geometry around the antimony atom, with the N atom strongly coordinated trans to a halogen atom. Different degrees of association through asymmetric Sb–X⋯Sb bridges [overall distorted square-pyramidal (C,N)SbX₃ cores] were found in the crystal of the dichloride 4 (polymeric chains) and dibromide 5 and diiodide 6 (centrosymmetric dimers), respectively. In an attempt to obtain [R₃SbI]I₃ by addition of I₂ to R₃Sb in 2 ∶ 1 molar ratio, deep red-brown crystals of the new ionic species [R₃SbOH]⁺[I₃]⁻ (7) have been isolated. Crystals of 7 are built up from [R₃SbOH]⁺ cations and linear non-symmetric [I₃]⁻ anions.

Cleavage of the Se–Se bond in [2-{O(CH₂CH₂)₂NCH₂}C₆H₄]₂Se₂ (1) and [2-{MeN(CH₂CH₂)₂NCH₂}C₆H₄]₂Se₂ (2) by treatment with SO₂Cl₂, bromine or iodine (1 : 1 molar ratio) yielded [2-{O(CH₂CH₂)₂NCH₂}C₆H₄]SeX [X = Cl (3), Br (4), I (5)] and [2-{MeN(CH₂CH₂)₂NCH₂}C₆H₄]SeI (6). The compounds were characterized in solution by NMR spectroscopy (¹H, ¹³C, ¹⁵N, ⁷⁷Se, 2D experiments). The solid-state molecular structures of 1–3, 4·HBr, 5 and 6 were established by single crystal X-ray diffraction. In all cases T-shaped coordination geometries, i.e. (C,N)SeSe (1, 2), (C,N)SeX (3, 5, 6; X = halogen) or CSeBr₂ (4·HBr), were found. Supramolecular associations in crystals based on hydrogen contacts are discussed.

Several families of heteroleptic tetrelenes of general formulae M(E^R^NMe2)[N(SiMe₃)₂] and M(O^E^R^NMe2)[N(SiMe₃)₂] (where E = S, Se; M = Ge, Sn, Pb; R^NMe2 = 2-(Me₂NCH₂)C₆H₄] supported by organochalcogenolato ligands have been prepared and fully characterised. The coordination chemistry of these ligands containing both hard (N, O) and soft (S, Se) atoms onto metals of varying size, polarisability, electropositivity and electrostatic surface potential has been explored. In the molecular solid-state, the complexes M(E^R^NMe2)[N(SiMe₃)₂] are monomeric, although an occurrence of weak Pb⋯Se intermolecular interactions yielding a bimolecular species has been identified in the case of the plumbylene Pb[SeC₆H₄(CH₂NMe₂)-2][N(SiMe₃)₂]. On the other hand, all complexes M(O^E^R^NMe2)[N(SiMe₃)₂] form centro-symmetric bimetallic dimers with O-bridging atoms. Multinuclear (²⁹Si, ⁷⁷Se, ¹¹⁹Sn, ²⁰⁷Pb) NMR spectroscopy and crystallographic studies reveal that the metal preferably remains 3-coordinated in all these heteroleptic complexes with absence of coordination of N and S/Se atoms, unless severe depletion of electronic density onto the metal is enforced. Coordination of these heteroelements can thus be achieved either through replacement of α-CH₃ substituents (as in the ligand 2-(Me₂NCH₂)C₆H₄SeCH₂C(Me)₂O⁻) by electron-withdrawing α-CF₃ moieties (as in the ligand 2-(Me₂NCH₂)C₆H₄SeCH₂C(CF₃)₂O⁻), or else with recourse to the use of a cationizing agent leading to the formation of the ion pair [{2-(Me₂NCH₂)C₆H₄SeCH₂C(Me)₂O}Pb]⁺·[H₂N{B(C₆F₅)₃}₂]⁻ where the cationic metal complex is associated to a weakly-coordinating anion. The data collated herein provide compelling evidence that the coordination chemistry of divalent tetrel elements with ligands featuring both hard and soft donors cannot be reliably anticipated by sole use of general concepts such as the HSAB theory. The related metal complexes containing the rigid 8-(NMe₂)naphthalen-1-yl group are also discussed.