Tin(ii) fluoride vs. tin(ii) chloride – a comparison of their coordination chemistry with neutral ligands

Reaction of SnF2 in MeOH with the appropriate neutral N- or O-donor ligands produces SnF (2, 2'-bipy) 2SnF6, SnF (1, 10-phen) 2SnF4 and SnF2 (L) L = Me3PO, dmso or pyNO). The X-ray structures of SnF (2, 2'-bipy) 2SnF6, SnF (1, 10-phen) 2SnF4 and SnF2 (dmso), reveal trigonal pyramidal Sn (II) cores with longer fluorine bridges completing distorted 5- or 6-coordination. Attempts to prepare SnF2 adducts with various phosphine or diphosphine ligands in MeCN failed, whilst in CH2Cl2 solution complex reactions involving the solvent occurred. The NHC, 1, 3- (2, 6-di-isopropylphenyl) imidazol-2-ylidene (IDiPP) and SnF2 produced the imidazolium salt, IDiPPHSnF3, the crystal structure of which revealed the first example of a discrete trifluorostannate (II) ion. In contrast, diphosphine complexes of tin (II) chloride formed readily, including SnCl2Me2P (CH2) 2PMe2, SnCl2o-C6H4 (PMe2) 2, SnCl2o-C6H4 (PPh2) 2 and (SnCl2) 2 (μ-Ph2P (CH2) 2PPh2), which were characterised by X-ray crystallography. The structures of SnCl2Me2P (CH2) 2PMe2 and SnCl2o-C6H4 (PMe2) 2 reveal chloride-bridged dimers, but SnCl2o-C6H4 (PPh2) 2, although also dimeric, has very asymmetric diphosphine coordination best described as κ (1). The structures of (SnCl2) 2 (μ-Ph2P (CH2) 2PPh2) and of SnClo-C6H4 (AsMe2) 2SnCl3 reveal trigonal pyramidal cores, but with longer Sn···Cl bridges affording polymeric structures. The synthesis of SnCl2 (R3EO) 2 (R = Ph, E = P or As; and R = Me, E = P) are also reported, along with the structure of SnCl2 (Me3PO) 2, which contains distorted tetragonal pyramidal Sn (II) coordination. X-ray structures are also reported for (PMe3) 2CH2SnCl32 and Ph2P (H) (CH2) 2P (H) Ph2SnCl32, obtained as by-products from the attempts to synthesise phosphine complexes, as well as (o-C6H4 (PMe2) 2CH2I2. All complexes were characterised by microanalysis, IR and multinuclear NMR spectroscopy ( (1) H, (19) F (1) H, (31) P (1) H and, where solubility allowed, (119) Sn). Comparisons are drawn with corresponding Sn (IV) and Ge (II) complexes.