Vincent A. Patrick

Quantitative Determination of Aqueous Dodecatungstophosphoric Acid Speciation by NMR Spectroscopy

The speciation and equilibria during base decomposition of α-[PW12O40]3– have been determined using 31P and 183W NMR spectroscopy over the pH range 0.7–13.5. NMR spectroscopy was used to directly observe the polytungstate species in aqueous solution at high concentration (0.25 mol L–1) and follows the progressive decomposition of [PW12O40]3– to WO42– and PO43–. It was found unexpectedly in the pH range 1.2–2.3 that [PW12O40]3– did not decompose directly to [PW11O39]7– but first formed an equilibrium with [P2W18O62]6–, [P2W21O71]6–, and some new, stable, intermediate species before converting into α-[PW11O39]7–.

Lewis-base adducts of Group 1B metal(I) compounds. Part 19. Crystal structures of bis(1,10-phenanthroline)copper(I) perchlorate and dibromocuprate(I)

The crystal structures of the title compounds [Cu(phen)2][ClO4](1) and [Cu(phen)2][CuBr2](2)(phen = 1,10-phenanthroline) have been established by single-crystal X-ray diffraction methods at 295 K. Crystals of (1) are monoclinic, P2/c, a= 10.037(3), b= 14.518(6), c= 7.672(3)Aβ= 97.82(3)°, Z= 2. R was 0.056 for 709 independent ‘observed’ reflections. Crystals of (2) are monoclinic, C2/c, a= 17.206(4), b= 13.365(2), c= 10.920(3)A, β= 115.43(2)°, Z= 4. R was 0.048 for 1 091 independent ‘observed’ reflections. Surprisingly, complex (2) is not a di-µ-bromo- bridged dimer, [(phen)CuBr2Cu(phen)], but ionic [Cu(phen)2][CuBr2]. In both (1) and (2), the [Cu(phen)2]+ cation has crystallographic 2 symmetry; in (1), the 2 axis passes through the ligands so that the overall symmetry is close to 222, but in (2) it passes between the ligands, so that the cation geometry is very far removed from 222 symmetry. In (1), Cu–N are 2.045(8), 2.053(9)A; in (2), 2.006(8) and 2.071(5)A. The linear anion in (2) has Cu–Br 2.209(2) and 2.223(2)A. The dihedral angles for each compound differ significantly, being 49.9° for (1) and 76.8° for (2), the former being the lowest value yet observed for a copper(I) cation with two bidentate ligands.

Quantitative Determination of Sodium Dodecatungstosilicate Speciation by 183W Nuclear Magnetic Resonance Spectroscopy

The speciation and equilibria of sodium dodecatungstosilicate has been determined using 183W nuclear magnetic resonance (NMR) spectroscopy over the pH range 3-13.5. The use of NMR allowed the direct observation of polytungstate anions in aqueous solution and at high concentration (0.5 mol L-1). Using this technique, the speciation of α-[SiW12O40]4-, α-[SiW11O39]8-, α-[NaSiW11O39]7-, α-[H2W12O40]6-, [H8W11O40]6-, [H7W11O40]7-, [W7O24]6-, [H2W12O42]10-, and WO42- was quantified as a function of pH. This work has allowed stability constants for α-[SiW12O40]4- (log K 46) and α-[SiW11O39]8- (log K 86) to be estimated.

Naturally occurring dibenzofurans. Part 3. On the structures of the rhodomyrtoxins

The degradation product of rhodomyrtoxin and ψ-rhodomyrtoxin, metabolites of the fruit of Rhodomyrtus macrocarpa Benth., previously assigned the structure 1,3,7,9-tetramethoxy-2,8-dimethyldibenzofuran (13) is now shown to be 1,3,7,9-tetramethoxy-4,6-dimethyldibenzofuran (15), the structure of this compound being determined by X-ray diffraction. By the synthesis of 1,1′-(1,3,7,9-tetrahydroxy-2,6-dimethyldibenzofuran-4,8-diyl)-3,3′-dimethyldibutan-1-one (17) and 1,1′-(1,3,7,9-tetrahydroxy-4,6-dimethyldibenzofuran-2,8-diyl)-2,3′-dimethyldibutan-1-one (2), structure (18), 1,1′-(1,3,7,9-tetrahydroxy-2,8-dimethyldibenzofuran-4,6-diyl)-3,3′-dimethyldibutan-1-one (18), is proposed for rhodomyrtoxin, and structure (1), 1,1′-(1,3,7,9-tetrahydroxy-2,8-dimethyldibenzofuran-4,6-diyl)-2,3′-dimethyldibutan-1-one (1), is confirmed for ψ-rhodomyrtoxin.

Stereochemistry and Crystal Structures of Bis Cycloadducts of Danishefsky's Diene (Me3SiOC(=CH2)CH=CHOMe) with 2,5- and 2,6-Dichlorobenzoquinone

Syntheses and single crystal X-ray structural characterizations are reported for bis adducts (6) and (7) formed between Danishefskys diene (8) with (respectively) the dienophiles 2,6- and 2,5-dichlorobenzoquinone. Formation of each adduct involves diastereocontrolled creation of six stereogenic centres.

Lewis-base adducts of Group 1B metal(I) compounds. Part 17. Synthesis and crystal structures of adducts of copper(I) cyanide with nitrogen bases

Compounds of the type [Cu(CN)Ln][L = diethylamine, (1), triethylamine, (2), 4-methylpyridine, (3), or 1,10-phenanthroline, (4)] have been synthesized by recrystallization of copper(I) cyanide from (or with) the parent base and their crystal structures have been determined by single-crystal X-ray diffraction methods; n= 1 except in the case of (3) where n= 1.5. Crystals of (1) are monoclinic, space group P21/n, with a= 15.108(7), b= 7.321(5), c= 13.699(6)A, β= 103.00(4)°, and Z= 8; R was 0.044 for No= 871 independent ‘observed’ reflections. For (2), crystals are orthorhombic, space group Pnma, with a= 9.501(4), b= 8.921(4), c= 11.279(5)A, and Z= 4; R= 0.039, No= 369. For (3), crystals are monoclinic, space group Cc, with a= 9.587(3), b= 16.326(4), c= 14.022(4)A, β= 109.38(2)°, and Z= 4; R= 0.031, No= 1 070. For (4), crystals are trigonal, space group P31, with a= 9.175(5), c= 11.753(8)A, and Z= 3; R= 0.041, No= 812. All complexes are one-dimensional polymers, that in (2) being disposed completely in a mirror plane except for the substituent alkyl groups. Copper atoms in (1) and (2) are trigonally planar co-ordinated by C,N(cyanide) and N(base), as is one of the two copper atoms in (3); the other copper atom in (3) is unusual, being four-co-ordinated pseudo-tetrahedrally by C,N(cyanide) and two N(base). A similar copper environment is found in (4).

(4α,4aβ,9aβ)-4a-Acetoxy-4-methoxy-3,4,4a,9a-tetra­hydro-1H-anthracene-2,9,10-trione

The relative stereochemistry of the title compound is defined by a room-temperature single-crystal X-ray study.