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The crystal structure of the title compound (NEt4) [Bi(S2COEt)4] has been determined by single-crystal X-ray diffraction at 295(1) K and refined by least squares to a residual of 0.051 for 1560 ?observed? reflections. Crystals are monoclinic, P21, a 10.947(2), b 16.334(4), c 10.589(2)Ǻ, β 116.04(2), Z 2. The bismuth coordination stereochemistry is dodecahedral, Bi-S ranging from 2.803(11) to 2.972(10) Ǻ; the three longest distances occupy a triangular face in the coordination polyhedron and may indicate the presence of a stereochemically active lone pair.

The isolation and structural elucidation of 3?-(2?-acetyl-3?-hydroxy- 5?-methoxy-4?methylphenoxy)-2?,4?-dihydroxy-6?-methoxy-5?- methylacetophenone (leprolomin) (12), an unusual lichen metabolite probably derived biogenetically by C-O phenolic coupling of two units of C-methylphloroacetophenone, is reported. Spectroscopic data on leprolomin and its derivatives allowed the structure to be limited to six possibilities; hence the crystal structure of leprolomin triacetate (15) was determined by X-ray diffraction.

The crystal structure of the title compound, [Tl(S2CNEt2)3], has been determined by single-crystal X-ray diffraction methods at 295 K and refined by full-matrix least squares to a residual of 0.050 for 2517 ?observed? reflections. Crystals are monoclinic, with space group A2/a, a 14.789(7), b 10.428(4), c 18.207(9) Ǻ, β 118.11(4), Z 4, and are isostructural with those of the previously determined gallium and indium analogues, the molecule having 2 symmetry with 2.666 Ǻ. As in the dimethyl/thallium analogue, the departure of the TlS6 core symmetry from 3 is large and is examined in terms of electron-pair repulsion theory.

Tin(II) xanthates form adducts with donor molecules and react with excess xanthate to form the tris-xanthato ion, Sn(EtOCS2)3-. No such reactions are observed with tin(IV) xanthates. Reaction of quinolin-8- ol with tin(IV) ethylxanthate results in the replacement of two xanthate moieties by two oxinato ions. The crystal structure of [Sn(EtOCS2)4] has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.038 for 2378 ?observed? reflections. The tin(IV) coordination environment resembles that observed in the N,N- diethyldithiocarbamate analogue, two of the xanthate ligands being monodentate and coordinating cis [Sn-S, 2.488(2), 2.499(2) Ǻ] in the six-coordinate coordination sphere while the other two ligands are bidentate, the Sn-S distances trans to the monodentate ligands being slightly longer [2.617(2), 2.627(2)Ǻ] than the other two [2.562(2), 2.539(2)Ǻ]. Crystals are monoclinic, P21/c, a 10.341(5), b 10.465(4), c 21.88(1) Ǻ, β 98.36(4), Z 4.

X-ray crystallographic analysis has revealed that the light-sensitive form (A) and the light-stable form (A?) of tetrabenzoylethylene are not valence tautomers but are two crystalline modifications of the same substance. The difference in the stability of these forms to light appears to be a consequence of their different molecular conformations and packing in the solid state. The molecular conformation of the A form is represented by (8) and that of the A? form by (9). The related tetraacetylethylene has the conformation (10) in the solid state. X-ray crystallographic analysis has also revealed that the photolysis product (B) of tetrabenzoylethylene is 4-phenoxy-3,4,6-triphenyl-1H,4H- furo[3,4-c]-furan-1-one (11). The crystal structures of (8), (9), (10) and (11) were determined by X-ray diffraction: diffractometer data at 295 K were refined by least-squares techniques to residuals of 0.064 (2161 ?observed? reflections) for (8), 0.057 (1310) for (9), 0.049 (1295) for (10) and 0.061 (1639) for (11). Crystals of (8) are monoclinic, P21/n, a 8.775(5), b 17.352(9), c 30.985(8)Ǻ, β 93.01(3), Z 8. Crystals of (9) which contain carbon disulfide are monoclinic, A2/a, a 21.21(2), b 6.181(4), c 20.35(2) Ǻ, β 102.77(7), Z 4. Crystals of (10) are monoclinic, P21/n, a 7.540(2), b 4.392(2), c 14.770(4) Ǻ, β 96.29(2), Z 2. Crystals of (11) are monoclinic, P1/n, a 14.820(4), b 15.000(3), c 10.819(4)Ǻ, β 106.02(2), Z 4.

The synthesis and some properties of N-(pyrrol-1-y1)maleimide (1) and its isomer (6) are described. The structure of 2-(pyrrol-1-yl)-4,7- dihydro-4,7-epoxyisoindole-1,3(7aH,3aH)-dione (8), a key intermediate in the synthesis of (1), has been determined by single-crystal X-ray diffraction at 298 K, and refined by least squares to a residual of 0.046 for 1977 ?observed? reflections. Crystals are triclinic, Pī, a 8.472(5), b 10.130(6), c 12.760(8) Ǻ, α 91.12(5), p 92.09(5), γ 102.90(4), Z 4.

The crystal structure of the title compound, NH4 [Co(NH3)4(SO3)2],3H2O, has been redetermined using diffractometer data at 295 K and refined by full-matrix least squares to a residual of 0.056 for 2068 ?observed? reflections. Crystals are orthorhombic, P212121, a 10.978(4), b 17.552(7), c 6.828(3)Ǻ, Z 4. The redetermined structure provides accurate structural data for the cobalt environment; as well, it locates all hydrogen atoms and defines cations and water molecules un- ambiguously. Co-S are 2.224(2), 2.221(2) Ǻ. Co-N (trans to S) (1.993(6), 2.023(6) Ǻ) are longer than the mutually trans Co-N (1.970(7), 1.977(6) Ǻ); the difference in the former is a consequence of lattice hydrogen bonding.

The crystal structure of the title compound, [Co(C2N2H8)2(C3N2H4)(SO3)] ClO4,2H2O has been determined by X-ray diffraction, using diffractometer data, at 295 K, and refined by full-matrix least squares to a residual of 0.071 for 3425 ?observed? reflections. Crystals are orthorhombic, Pcmn, a 15.822(9), b 11.924(6), c 9.261(2) Ǻ, Z 4. The imidazole and sulfite ligands are trans in the cation, which has m symmetry (Co-S 2.223(2); Co-N 2.008(4) Ǻ). is 1.964Ǻ. The apparent thermal motion of the sulfite about the Co-S axis is very high. The internal internuclear distances are compared to the data reported for series of similar complexes in which trans effects are observed.

The crystal structure of 7-t-butyl-3-(5?-t-butyl-3?-methylfuran-2?-yl)- 5-methylbenzofuran-2(3H)-one, C22H28O3, has been determined at 295 K from diffractometer data and refined by least squares to a residual of 0.062 for 1830 ?observed? reflections. Crystals are triclinic, Pī, a 11.210(3), b 9.742(3), c 9.389(4) Ǻ, α 88.02(3), β 85.32(3), γ 77.13(2), Z 2.

The preparation and crystal structure determination of the adduct [Sb(S2COEt)3],0.5C10H8N2 is reported. Crystals are triclinic, Pī, a 6.064(3), b 10.825(6), c 17.723(7) Ǻ, α 104.77(4), β 96.78(3), γ 97.14(4), Z 2. The compound is a lattice adduct, the bipyridyl molecule being located about a crystallographic centre of symmetry. The complex molecule geometry is unlike that of the compound [Sb(S2COEt)3]; in the latter the molecule has crystallographic symmetry 3, the three equivalent ligands being unsymmetrically coordinated, while in the present molecule the chirality is lost, the molecule conforming to approximate pseudo-m symmetry: two ligands are similar [Sb-S, 2.615(2), 2.892(2); 2.612(2), 2.878(2) Ǻ] and the other, located in the pseudo-mirror plane, is different [Sb-S, 2.477(2), 3.091(2) Ǻ]. Electron-pair repulsion theory shows that the bond angles, the relative bond lengths, and the coexistence of different stereoisomers of this molecule, can be ascribed to the stereochemically active lone pair of electrons being close to the antimony atom.

The crystal structures of the title compounds, PhCOCH=NOH (5) and Na+[MeCOC(=NO-)CO2Et],-2H2O (10), have been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to R 0.051, 0.062 (815, 1199 ?observed? reflections) respectively. Crystals of (5) are monoclinic, P21/n, a 14.177(6), b 5.075(4), c 11.049(6) Ǻ, β 112.89(3), Z4. Crystals of (10) are tetragonal, I41/a, a 19.41(1), c 10.643(5)Ǻ Z 16. In (5), within the C=NOH group, C-N is 1.263(4) and N- O is 1.375(4)Ǻ; in (10) C-N is 1.318(6) and N-O is 1.321(5)Ǻ. In (10), the (presumably) negative C=NO- group does not coordinate the sodium ion; the latter is bridged by water molecules, occupying four close coordination positions [2.405(4)-2.552(4)Ǻ] in an interesting bridged polymeric array while the remaining two coordination positions are occupied by two ligand C=O groups [2.363(4), 2.393(4) Ǻ], the ligands also bridging sodium ions.

The crystal structure of the title compound, C18H18O5, has been determined by single-crystal X-ray diffraction methods at 295 K and refined by least squares to a residual of 0.058 for 1502 ?observed? reflections. Crystals are monoclinic, P 21/n, a 22.048(6), b 7.075(2), c 10.443(3) Ǻ, β 100.40(3), Z 4. The structure was solved by a combination of special direct phasing procedures and translation functions, after conventional direct methods had failed.

Crystals of methanethiolatomercury(II) acetate are monoclinic, P 21/c, with a 5.292(2), b 15.912(7), c 7.086(2) Ǻ, β 92.96(3), Z 4, and its pyridine complex MeSHgO2CMe,C5H5N is monoclinic, P21/n, with a 10.093(3), b 7.026(2), c 15.350(5) Ǻ, β 105.01(3), Z4. Both structures are based on a polymeric chain (-Hg-SMe-)n with coordinated acetate groups. In MeSHgO2CMe the chains are linked into sheets by bridging acetate groups, and in the pyridine complex the chains are isolated with pyridine and acetate coordination at each mercury. Crystals of (ButS)4Cl4Hg4(C5H5N)2 are triclinic, Pī, with a 14.399(6), b 9.893(6), c 9.597(5) Ǻ, α 121.82(1), β 102.52(4), γ 102.94(4), and Z 1. The structure is based on a tetranuclear grouping of mercury atoms bridged by chloride and thiolate species and centrosymmetric about the origin. There are two mercury environments ?Hg(μ-SBut)2ClN? and ?Hg(μ-SBut)2(μ-Cl)2? with the dichloro bridge linking two equivalent mercury atoms on opposite sides of an (-Hg-SBut-)4 ring.

The crystal structure of the title compound has been determined at 295 K by single-crystal X-ray diffraction methods and refined by least- squares techniques to a residual of 0.049 for 1046 ?observed? reflections. Crystals are monoclinic, P21/c, a 11.584(6), b 5.449(7), c 15.273(8) Ǻ, β 92.44(4), Z4. The pair of quinol hydrogen atoms are both located on the one benzene ring as the title indicates.

The crystal structure of the title compound, [Fe{CS2N(CH2)4}3] (a new phase prepared from chloro-form/toluene solutions), has been determined by single-crystal X-ray diffraction at 295 K and refined to a residual of 0.059 for 5651 ?observed? reflections. Crystals are monoclinic, P21/a, a 18.033(6), b 9.398(2), c 13.176(6) Ǻ, β 100.80(3), Z 4. The compound is a purely high-spin derivative, the iron atom being in the usual pseudo-D3 environment with very long (2.456 Ǻ).

The crystal structures of PhHgL [L = quinaldinate, C10H8NO- (1); oxinate, C9H6NO-, two phases, (2) and (3)] have been determined at 295 K and refined by least squares to residuals of 0.068 (2148 ?observed? reflections) for (1), 0.107 (1165) for (2) and 0.046 (1146) for (3). Crystals of (1) are mono-clinic, C2/c, a 22.961(8), b 9.142(2), c 16.412(6) Ǻ, β 127.75(2), Z 8; those of (2) are orthorhombic, Pnam, a 23.12(3), b 16.59(2), c 6.62(1) Ǻ, Z 8; those of (3) are orthorhombic, P212121, a 5.584(2), b 9.902(3), c 22.073(9) Ǻ, Z 4. In (1) the molecules are grouped as loose dimeric associations about a twofold axis with Hg...O bridges. In (2) the molecules lie stacked in a loose infinite array along c, while in (3) the disposition is an infinite helical array; in both (2) and (3), the Hg...O contacts are very long.

The crystal structure of the title compound, [Ni(en)3] (ClO4)2,H2O, has been determined from single-crystal X-ray diffraction data at 295(1) K and refined by least squares to a residual of 0.093 for 1400 ?observed? reflections. Crystals are orthorhombic, P bca, a 17.043(7), b 15.922(6), c 13.496(5) Ǻ, Z 8. The precision of the structure determination is adversely affected by very high perchlorate thermal motion. is 2.13 Ǻ.

In connection with studies on possible mesoionic systems, syntheses of 1,3-bis(4?-bromophenyl)-propane-1,2,3-trione (5), 3,5-diphenyl-1,2- dithiolylium-4-olate (9) and 4-hydroxy-3,5-diphenyl-1,2-dithiolium perchlorate (10) have been reexamined. The crystal structures of (5), (9) and (10) have been determined by X-ray diffraction from diffractometer data at 295 K and were refined by full-matrix least squares to residuals of 0.050 (1118 ?observed? reflections), 0.072 (2388) and 0.087 (2000), respectively. Crystals of (5) are monoclinic, C2/c, a 18.535(4), b 7.734(2), c 12.184(3) Ǻ, β 126.60(3), Z 4. Crystals of (9) are orthorhombic, Pmcn, a 26.047(6), b 7.170(2), c 6.431(2) Ǻ, Z 4. Crystals of (10) are monoclinic, P21/a, a 18.601(7), b 10.636(4), c 8.152(2) Ǻ, β 102.60(3), Z 4. In (5) π-character is localized in the phenyl rings and carbonyl groups [ 1.22(1) Ǻ] and the substance is best represented as a normal vicinal triketone. In (9) and (10) S-S bonds are present and (9) is correctly regarded as a heterocyclic system. The geometry of the heterocyclic ring in (10) agrees well with that previously found for the 1,2-dithiolium cation; is 1.35(1) Ǻ. In (9) the heterocyclic C-C distances [1.442(2)Ǻ] are longer than in (10); this indicates diminished aromaticity on deprotonation. The C-C-C angle [111.2(2)] in (9) is also smaller than that [118.3(8)] in (10) and in (9) is 1.250(3) Ǻ. The behaviour of 1,3-diphenylpropane-1,2,3-trione (4) and (9) with acetylenic dipolarophiles has been studied but no evidence has been obtained that either substance undergoes a 1,3-dipolar cycloaddition reaction.

The title compound, (Et4N) [Co(S2CO)(S2COEt)2], and its chromium analogue have been prepared by nucleophilic attack of (Et4N)(S2COEt) on the parent tris(ethylxanthato)metal(III) complex in acetone solution, the structure of the cobalt derivative being confirmed by single-crystal X- ray structure determination; the structure was refined by least squares to a residual of 0.045 for 2306 ?observed? reflections. Crystals are orthorhombic, P bca, a 17.303(8), b 16.970(6), c 16.052(6) Ǻ, Z 8. for the ethylxanthate ligands is 2.286 Ǻ, longer than in the parent tris(ethylxanthato)-cobalt(III) complex, while for the dithiocarbonate, chelated through the two sulphurs, is 2.251 Ǻ.

The crystal structures of [(en)2NiCl2Ni(en)2] Cl2 (1) and [(en)2NiCl2Ni(en)2] (ClO4)2 (2) have been redetermined from single- crystal X-ray diffraction data at 295(1) K and refined by least squares to residuals of 0.073 and 0.052 respectively for 1345 and 1605 ?observed? reflections respectively. Crystals of (1) are monoclinic, P21/n, a 14.053(4), b 11.309(3), c 6.326(1) Ǻ, β 94.22(2), Z 2. Crystals of (2) are monoclinic, P21/n, a 8.885(12), 6 19.707(20), c 7.120(8) Ǻ, β 108.99(4), Z 2. In both (1) and (2), a dimeric complex cation is observed, a pair of cis coordination sites about the nickel in each case being occupied by the bridging chlorines; the latter are asymmetric (Ni-Cl, 2.461(3), 2.551(3)(1); 2.461(3), 2.512(3) Ǻ (2)).

The crystal structure of the title compound, CZOH3803 [compound (1) in ref.'], has been determined by single-crystal X-ray diffraction at 295(1) K and refined by least squares to a residual of 0.045 for 954 'observed' reflections. Crystals are monoclinic, P2', a 9.281(2), b 17.798(6), c 6.417(1) A, B 93.81(3)", Z 2. The structure determination establishes the relative configuration of the chiral centres within the 14-membered macrocyclic ring and shows the double bond to have the unusual (Z) configuration.

The crystal structure of the title compound has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.064 for 775 ?observed? reflections. The structure determination confirms the stereochemistry previously proposed for the molecule. Crystals are monoclinic, P21/n, a 11.131(7), b 18.908(3), c 7.121(5) Ǻ, β 104.56(5), Z 4.

The crystal structure of the quinone A, C15H14O6, derived from protoaphin-fb, has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.051 for 758 ?observed? reflections. Crystals are monoclinic, P21, a 5.239(4), b 16.551(9), c 7.920(8) Ǻ, β 108.92(6), Z 2. The structure determination confirms that proposed chemically, including the chirality of all asymmetric centres in the molecule.

The crystal structures of the title compounds, o-C6H4(AsMeI)2 (1), and o- C6H4(AsMeI)2- [o-C6H4(AsMe)(As+Me2)O] I- (2), have been determined at 295 K by single-crystal X-ray diffraction and refined by least squares to residuals of 0.037 and 0.067 for 2095 and 2913 reflections respectively. Crystals of (1) are triclinic, Pī, a 9.865(5), b 9.837(7), c 7.765(4) Ǻ, α 98.89(5), β 96.71(4), γ 60.72(4), Z 2. is 2.585 Ǻ and 1.97 Ǻ. The angles about the arsenic differ only trivially, the mean being 98.4. Crystals of (2) are monoclinic, P21/n, a 15.315(4), b 21.511(8), c 7.952(2) Ǻ, β 98.19(2), Z 4. In the cation As-O distances are unequal [1.75(1) (quaternary As), 1.86(2) Ǻ]; As-O-As is very small being 115.8(8). Charge-transfer interactions between iodine species are present in both derivatives; in (2), there is an interaction between the tertiary arsenics of the meso molecule and the iodide anion, As...I being 3.307(3), 3.551(3) Ǻ, with the geometry of the arsenics approaching that of a tetrahedral disposition. Within the cation, the geometry about the quaternary arsenic is typical of arsenic(v), the bond lengths being shorter than those about the ternary arsenic.

The crystal structure of the title compound, C15H15IO5, has been determined by single crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.04 (2210 ?observed? reflections). Crystals are monoclinic, P21/c, a 10.294(5), b 18.868(9), c 7.549(6) Ǻ, β 90.29(5), Z 4. The molecular geometry apart from the iodine environment is as expected; the crystal packing is such that the iodine lies close to a symmetry-related neighbour at I...I 4.148(2) Ǻ and may account for the observed facile elimination of iodine from the solid on heating to 120C.

The crystal structure of the title compound, [Fe(CO)4(C10H8O)], has been determined at 295 K from diffractometer data, and refined by least squares to a residual of 0.073 for 2990 ?observed? reflections. Crystals are triclinic, Pī, a 22.980(6), b 9.385(3), c 6.313(2) Ǻ, α 85.22(3), β 87.67(3), γ 79.48(3), Z4. The two independent molecules in the same cell differ only trivially in their geometries, the coordination number about the metal being essentially five: four carbonyls and the ethylene double bond in a pseudo-trigonal-bipyramidal arrangement. From distortions observed within the molecular geometry as a result of steric interactions between the epoxide oxygen and the nearby axial carbonyl, it clearly emerges that the stability of the present derivative relative to that of methylene bridged ligands is simply a consequence of the greatly increased stereochemical interaction of the latter and not of any electronic effect.

The crystal structure of the title compound [Cr(CS2NEt2)3] has been determined at 295 K from X-ray diffractometer data and refined by least squares to a residual of 0.069 (3190 ?observed? reflections). Crystals are monoclinic, P21/n, a = 14.308(4), b = 10.389(4), c = 17.145(8) Ǻ, β = 110.92(3), Z = 4, and are isostructural with the ruthenium and iron(III) (room temperature) analogues. is 2.396 Ǻ.

The crystal structure of (E)-7-t-butyl-5-methoxy-3-[(E)-2?-methoxy- 5?,5?-dimethyl-4?-oxohex-2?enylidene]benzofuran-2(3H)-one, C22H28O5 (see preceding paper), has been determined by single-crystal X-ray diffraction at 295(1) K and refined by least squares to a residual of 0.067 (3735 ?observed? reflections). Crystals are triclinic, Pī, a 14.955(7), b 13.142(5), c 10.910(3) Ǻ, α 85.76(3), β 85.67(3), γ 80.12(3), Z 4.

The crystal structure of the title compound, C22H28O5, has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.075 (2101 ?observed? reflections). Crystals are triclinic, Pī, a 13.789(4), b 11.461(4), c 7.027(3) Ǻ, α 81.70(3), β 107.18(2), γ 99.10(3), Z 2. The structure is shown to be the Z,Z isomer, and its geometry is compared with that of the E,E isomer reported previously.

The crystal structure of the title compound, [Cu{CS(NH2)2}2(phen)] I,phen, has been determined by X-ray diffraction with direct methods, and refined by least squares to a residual of 0.043 for 5383 ?observed? reflections. Crystals are triclinic, Pī, a 13.263(8), b 12.449(2), c 10.214(2) Ǻ, α 113.20(2), β 90.16(2), γ 112.72(2), Z 2. The coordination about the copper is pseudo-tetrahedral, distorted by the bite of the phenanthroline ligand [Cu-S, 2.295(2), 2.280(1) Ǻ; Cu-N, 2.072(4), 2.089(5) Ǻ, N-Cu-N, 81.0(2); S-Cu-S, 117.31(6); N-Cu-S, 107.7(11)-117.23(9)]. In addition the structure provides the first example of the determination of the geometry of the uncoordinated o- phenanthro-line molecule. The stereochemistry of the [M(bidentate)(unidentate)2] coordination type is considered in terms of a repulsion model.

The crystal structure of the title compound, [Cu(C12H8N2)2I]I,S8, has been determined by X-ray diffraction at 295(1) K and refined by least squares to R 0.066 (2031 ?observed? reflections). Crystal data: orthorhombic, Pbcb, a 7.984(5), b 16.690(4), c 22.986(12) Ǻ, Z 4. The structure comprises five-coordinate trigonal bipyramidal [Cu(phen)2I]+ cations (I equatorial) lying on the 2 axes parallel to a which pass through the Cu-I bonds, together with iodide anions, and lattice S8 molecules, also lying on 2 axes but parallel to b. In the cation, Cu-I is 2.672(3), Cu-N (equatorial) 2.10(1) and Cu-N (axial) 2.00(1) Ǻ. S-S ranges from 2.004(7) to 2.059(7). There appears to be no significant interaction between the octasulphur molecules and any other species.

The crystal structures of the title compounds have been determined at 295(1) K by X-ray diffraction and refined by full-matrix least squares to residuals of 0.045 and 0.067 for 1224 and 1955 ?observed? reflections respectively. The compounds are isomorphous (triclinic, Pī, Z 1). Dichloro compound: a 8.068(2), b 8.024(2), c 7.646(2) Ǻ, α 93.84(2), β 113.44(2), γ 117.11(2). Dibromo compound: a 7.999(2), b 7.921(2), c 7.849(2) Ǻ, α 94.37(2), β 112.85(2), γ 115.99(2). The copper atoms are square-planar coordinated with two halide and two base ligands coordinated necessarily trans by virtue of the siting of the molecule on a centre of symmetry. Cu-X, Cu-N are 2.264(2), 2.011(3) (dichloro); 2.425(1), 1.997(4) Ǻ (dibromo). The plane of the lutidine is almost normal to the CuN2X2 plane.

The crystal structure of the title compound, namely hydroxyimino(N,N?- dimethyl)malonamide (MeNHCOC(=NOH)CONHMe), has been determined by single-crystal X-ray diffraction with diffractometer data at 295 K. The structure was solved by direct methods and refined by least squares to a residual of 0.055 for 1477 observed reflections. Crystal data: monoclinic, P21/n, a 15.508(3), b 10.544(2), c 9.377(1) Ǻ, β 103.15(2), Z 8. The two crystallographically independent molecules exhibit little conjugation throughout the C-C-C skeleton ( 1.50 Ǻ), the molecule being non-planar. is 1.234, 1.443, 1.323, 1.278 and (N-O) 1.375 Ǻ. The geometry is compared with those observed for several related derivatives.

The crystal structures of 1 : 1 adducts of cuprous iodide with collidine ICu(col) and 2,6-lutidine ICu(lut), and of cuprous chloride with pyridine ClCu(py), have been determined at 295 K and refined by full-matrix least squares to residuals of 0.052 [ICu(col)], 0.079 [ICu(lut)], 0.057 [ClCu(py)] for 465, 1761 and 720 ?observed? reflections respectively. Crystal data.-ICu(col), orthorhombic, P21mn, a 11.500(3), b 10.620(3), c 4.159(1) Ǻ, Z 2. ICu(lut), monoclinic, P21/c, a 16.377(9), b 7.833(3), c 15.401(8) Ǻ, β 110.53(4), Z 8. ClCu(py), monoclinic, P21, a 9.324(4), b 3.8484(7), c 8.663(4) Ǻ, β 107.08(3), Z 2. The 1 : 1 cuprous bromide-pyridine adduct BrCu(py) is isomorphous with ClCu(py): a 9.423(2), b 3.9585(6), c 8.907(2) Ǻ, β 108.13(2). In none of the three structures is the tetrameric (CuXL)4 species found. The structure of ICu(col) is an infinite zig-zag I-Cu-I-Cu- polymer running parallel to c; the copper is also coordinated by the collidine, Cu, I and N lying in the mirror y = 0.5 which also bisects the collidine ring. The structure of ICu(lut) comprises dimeric species, a pair of three-coordinated copper atoms being bridged by the two associated iodines. ClCu(py) has the ?ribbon? structure typified by CuCl,MeCN and CuBr,MeCN, an infinite polymer parallel to b. The inability of ICu(col) and ICu(lut) to form tetramers is attributed to steric hindrance of the methyl substituents of the base. The Cu-Cu distance in ICu(lut) is remarkably short (2.586 Ǻ).

The crystal structure of the title compound, C12H18, has been determined at 295 K by X-ray diffraction and refined by full-matrix least squares to a residual of 0.049 for 216 ?observed? reflections; molecular geometry has been corrected for the effects of thermal motion using a rigid body approximation. Crystals are hexagonal, P63/m, a = 6.582(1), c = 11.843(3) Ǻ, Z = 2, the molecules occupying a hexagonal close- packed array.

The crystal structures of the title compounds [Hg{Mo(CO)3(C5H5)}2] (1) and [IHg{Mo(CO)2- (C5H4Me)(AsPhMe2)}] (2) have been determined by X-ray diffraction at 295 K and refined by least squares to residuals of 0.065 and 0.079 for 867 and 1313 ?observed? reflections respectively. [Hg{Mo(CO)3(C5H5)}2] is monoclinic, C2/c, a = 21.161(5), b = 7.106(1), c = 12.103(2) Ǻ, β = 91.23(2), Z = 4. [IHg{Mo(CO)2(C5H4Me)(AsPhMe2)}] is monoclinic, P21/a, a = 24.784(8), b = 7.751(3), c = 9.949(3) Ǻ,β = 105.16(3), Z = 4. The molecule in (1) has symmetry 2. Coordination about the mercury is substantially linear in both cases: (1) Mo-Hg-Mo 173.71(6), Hg-Mo 2.746(2) Ǻ; (2) Mo-Hg-I 167.40(8), Hg-Mo 2.685(3), Hg-I 2.720(3), Mo-As 2.536(4) Ǻ.