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NMR chemical shifts of 1 H, 13 C, and 73 Ge, molecular modeling, and single-crystal X-ray diffraction results are reported for a series of substituted tris-and tetrakis(phenyl)germanes of the type (XC 6 H 4 ) 3 GeY and (XC 6 H 4 ) 4 Ge, where X = o-, m-, and p-OCH 3 , o-, m-, and p-OC 2 H 5 , m-and p-CF 3 , H, p-C(CH 3 ) 3 , p-Cl; and Y = Cl and H. Chemical shifts and X-ray data are also reported for o-CH 3 and o-OCH 3 tetrakis(phenoxy)-((XC 6 H 4 O) 4 Ge) and thiophenoxygermanes ((XC 6 H 4 S) 4 Ge). For tetrakis derivatives, 73 Ge resonances are observed for all but the o-methoxyphenoxy compound, for which the inability to detect a resonance is attributed to rapid quadrupolar relaxation caused by intramolecular interactions of the methoxy oxygen with the central atom. The observation of a relatively broad, slightly upfield 73 Ge resonance in the analogous phenyl and thiophenoxy derivatives suggests, as do the results of molecular modeling, that in these compounds there is some hypercoordination. The solid-state structures show bond angles at the aromatic carbon bearing the alkoxy group that suggest an interaction of the alkoxy oxygen with germanium. Oxygen-germanium bond distances are about 17% shorter than the sum of the van der Waals radii.

The literature contains considerable disagreements on the relative stabilities of the members of the copper hydroxyl sulphate family. Titration of copper sulphate with sodium hydroxide is claimed by some to produce only brochantite, while other reports indicate that antlerite and a dihydrate of antlerite are produced in the titration. Most stability field diagrams show that antlerite is the more stable stoichiomer at pH 4 and sulphate activity of 0.05À1. We have reexamined this stoichiometric family by titration of aqueous copper sulphate with sodium hydroxide and sodium carbonate, reverse titration of sodium hydroxide with copper sulphate and simultaneous addition of copper sulphate and sodium hydroxide at a variety of mole ratios, concentrations, temperatures and reaction times. We have also explored the reaction of copper hydroxide with copper sulphate and the reaction of weak bases, such as sodium acetate, sodium carbonate and urea, with copper sulphate. Our work indicates that: (1) antlerite is not formed in reactions of 0.05 to 1.2 M CuSO 4 with 0.05À1.0 M NaOH or Na 2 CO 3 at room temperature; (2) antlerite is formed in the addition of small concentrations of base (40.01 M) to 1 M CuSO 4 at 80ºC, but not at room temperature or with 0.01 M CuSO 4 at 80ºC; (3) the formation of Cu 5 (SO 4 ) 2 (OH) 6 .4H 2 O occurs at large Cu 2+ to base mole ratios; (4) the compound described in the literature as antlerite dihydrate is actually Cu 5 (SO 4 ) 2 (OH) 6 .4H 2 O; (5) at mole ratios of Cu 2+ to OH À ranging from 2:1 to 1:2 the predominant product is brochantite; and (6) brochantite and Cu 5 (SO 4 ) 2 (OH) 6 .4H 2 O are converted to antlerite in the presence of 1 M CuSO 4 (the latter requires temperatures of 80ºC or greater).The K sp (ion activity product) values of antlerite and brochantite were determined to be 2.53 (0.01)610 À48 and 1.01 (0.01)610 À69 , respectively, using atomic absorption spectroscopy and Visual MINTEQ after equilibration in solutions of varying ionic strength and pH for six days. These values are in good agreement with those from the literature. However, after 6 months, antlerite in contact with solution is partially converted to brochantite and hence is metastable with a relatively low conversion rate. The K sp value for antlerite must therefore be considered approximate. The relative stabilities of the copper hydroxyl sulphates are rationalized using appropriate equations and Gibbs energy calculations. A Gibbs free energy of formation for Cu 5 (SO 4 ) 2 (OH) 6 .4H 2 O of À3442 kJ/mol was obtained from the simple salt approximation. The very restricted conditions required for the formation of antlerite are rationalized with a stability field diagram at 80ºC.

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The lack of understanding of the structural and electronic factors that affect the often difficult to observe germanium resonance has been a major deterrent to studies of bonding interactions at germanium. We utilized the symmetrical system GeR 4 to determine what structural factors inherent in the R group affect the shape and position of the (73)Ge resonance. The (73)Ge resonances of symmetrical tetrakis germanium compounds of the type GeR 4 (R = alkyl, aryl), GeX 4 (X = F, Cl, Br, I), Ge(OR) 4 (R = alkyl, methoxyalkyl, dimethylaminoalkyl), Ge(NR 2) 4 (R = alkyl), and Ge(SR) 4 (R = alkyl, dimethylaminoalkyl) were examined for evidence of intramolecular coordination. Although many of these compounds have sharp resonances due to idealized tetrahedral symmetry with relatively long relaxation times, others have broad or no observable resonances due to fast quadrupolar relaxation. We hypothesize that the perturbation of symmetry by even weak Lewis interactions or conformational changes causes broadening of the resonance before the interaction can become sufficiently strong to cause the significant low-frequency shift generally associated with hypercoordination in most nuclei. Intermolecular coordination to GeCl 4 is believed to be responsible for the low-frequency shifts in (73)Ge resonances and the associated changes in peak widths in mixtures with bases such as tributylphosphine oxide (TBPO) and triethylphosphine oxide (TEPO). Adduct formation with these bases is confirmed by broad (31)P resonances that are resolved into five peaks at -40 degrees C. The exchange-broadened resonances due to the 1:1 and 1:2 TEPO adducts are also observed at -40 degrees C in the (73)Ge spectrum. Thus, relatively strong bonding to the germanium in GeCl 4 results in both low-frequency shifts and broadening of the resonance. The broad (73)Ge resonances that occur in some compounds may be in part due to exchange as well as quadrupolar relaxation.

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