I This work was supported by the Science and Engineering Research Council (Research Studentship for GAG) and the Northern Ireland Department of Education (Research Studentship for PPM). 264 0 VCH Verlag.~gesellschaji mbH. 0-6940 Weinheim. 1987 0570-0833/87/0303-0264 $ 02.50/0 Angew. Chem. lnr. Ed. Engl. 26 (1987) No. 3

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38- [C11HtsN2][CuBr4].H20 AND [NH2(CH3)(CsH9)I2 [CuBr 4] reported in this paper, the dihedral angle is 51.6 ° and the geometry of the CuBr 2-ion, although intermediate between square planar and tetrahedral, is nearer to square planar than the high-temperature form of the CuC12-salt. The N-Br distance is 3.480 A (ave.) and the H--Br distance is 2.66A (ave.). In other compounds studied in this laboratory, where both the CuCI 2-salt and the CuBr 2-salt of the same cation have been prepared, the tetrabromocuprate(II) ion has usually shown a larger dihedral angle than the tetrachlorocuprate(II) ion (Table 6). This is as expected for the larger Br atom since distortion towards a tetrahedral geometry will lessen ligand-ligand repulsions. This argument would hold for the bis(NMPH) salts if the tetrabromocuprate(II) is compared directly with the low-temperature form of the tetrachlorocuprate(II). The high-temperature form contains disordered organic cations which exhibit decreased hydrogen bonding; it is therefore able to adopt a more tetrahedral configuration. The role of hydrogen bonding in CuC12-ions has been discussed previously (Geiser & Willett, 1984), and in CuBr~-versus CuC12-ions (Place & WilieR, 1987a).In the NMPH salt, the distances and angles within the cations are normal. The lattice is held together with hydrogen bonding between the ammonium nitrogen N(9) and the Br ions. The N(9)-Br(1) distance is 3.485, H(9A)--Br(1) is 2.726 A. N(9)-Br(2) is 3.476, H(9B)--Br(2) is 2.593 A. The packing shows distinct layers of anions and cations. The 2-phenylethyl groups form a contiguous layer with the charged methylammonium group alternating either side of, and protruding from, this layer.

The reaction of [Mn(OAsPh,),l,] with sulphur dioxide in toluene yields [Mn(OAsPh,),(O,SI),)]. Two unexpected products, [( Ph,AsO),H] I, and [AsPhJ] I, , have been isolated from the reaction filtrate.