The contributions of terephthalic acid and Zn(2+)-coordinated water in N,N-diethylformamide (DEF) to the overall proton activity in the synthesis of MOF-5 (Zn4O(BDC)3, BDC = 1,4-benzenedicarboxylate) were quantitatively determined by combined electrochemical and UV-vis spectroscopic measurements. Structural transformations of zinc carboxylate-based metal organic frameworks due to their exposure to environments with variable water concentrations and the chemical means necessary to revert these transitions have been investigated. It was found that the water-induced structural transition of MOF-5 to the hydroxide structure Zn3(OH)2(BDC)2 x 2 DEF (MOF-69c) can be reverted by a thermal treatment of the obtained compound and its subsequent exposure to anhydrous DEF. MOF-5 syntheses from simple carboxylates as well as a water-free synthesis based on nitrate decomposition are presented. The latter demonstrates that nitrate can serve as the sole source for the oxide ion in MOF-5.

The tautomerism of cyameluric acid C6N7O3H3 (1 a), cyamelurates and other heptazine derivatives has recently been studied by several theoretical investigations. In this experimental study we prepared stannyl and silyl derivatives of cyameluric acid (1 a): C6N7O3[Sn(C4H9)3]3 (3 a), C6N7O3[Sn(C2H5)3]3 (3 b), and C6N7O3[Si(CH3)3]3 (4). In order to investigate the structure of 1 a the mono- and dipotassium cyamelurate hydrates K(C6N7O3H2)2 H2O (5) and K2(C6N7O3H)1 H2O (6) were synthesized by UV/Vis-controlled titration of a potassium cyamelurate solution with aqueous hydrochloric acid. Compounds 3-6 were characterized by FTIR and solid-state NMR spectroscopy as well as simultaneous thermal analysis (TGA, DTA). The single crystal X-ray structures of the salts 5 and 6 show that the hydrogen atoms in both anions are localized on the peripheral nitrogen atoms. This indicates-in combination with the solid-state NMR studies-that the most stable tautomer of solid 1 a is the triketo form with C3h symmetry. However, derivatives of both the hydroxyl and the amido tautomers may be formed depending on the substituent atoms: The spectroscopic data and single crystal structures of compounds C6N7O3[Si(CH3)3]3 (4) and the solvate C6N7O3[Sn(C2H5)3]3C2H4Cl2 (3 b') show that the former is derived from the symmetric trihydroxy form of 1 a, while 3 b' crystallizes as a chain-like polymer, which contains the tin atoms as multifunctional building blocks, that is, bridging pentacoordinated Et3SnO2 and Et3SnON units as well as non-bridging four-coordinated Et3SnN units. The cyameluric nucleus is part of the polymeric chains of C6N7O3[Sn(C2H5)3]3C2H4Cl2 (3 b'), by the action of both tautomeric forms of cyameluric acid, the amide and the ester form.

7-Azaindole (H-azain) reacts with sodium borohydride (NaBH4) to yield the sodium salt of the novel 7-azaindol-7-ylborate anion (7-azain-7)BH3 −, two rhodium derivatives of which reveal distinct coordination modes  [Rh{κ2 N,H-H3B(7-azain-7)}(CO)(PPh3)2] and [Rh{κ3 N,H,H′-H3B(7-azain-7)}(PPh3)2]thereby demonstrating how the variable denticity of the ligand may accommodate the varying electronic requirements of the metal center.

Reaction of 2-LiC6F4PPh2 with [MCl2(SEt2)2] in diethyl ether gives the monomeric bis(chelate) complexes trans-[M(κ2-2-C6F4PPh2)2] [M = Pt (1), Pd (2)] or, in the case of platinum, a mixture of cis- and trans-isomers. Treatment of a mixture of NiCl2 and 2-BrC6F4PPh2 in THF with zinc dust gives trans-[Ni(κ2-2-C6F4PPh2)2] (3). The four-membered chelate rings in 1−3 are opened on addition of the bidentate ligand 1,2-bis(diphenylphosphino)ethane (dppe), and, in the case of 3, 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen), to give complexes of the type cis-[M(κC-C6F4-2-PPh2)2(L-L)] [L-L = dppe, M = Ni (6), Pd (7), Pt (8); M = Ni, L-L = bipy (9), phen (10)], in which the PPh2 groups are uncoordinated. Complexes 6−8 show unexpectedly large four-bond coupling constants (4 J PF), in the range 75−95 Hz, between the fluorine atoms (F6) ortho to the metal−carbon σ-bond and the phosphorus atoms of the PPh2 groups, possibly because F6 and the lone pairs on phosphorus adopt a close to synperiplanar conformation. Treatment of 2 with [PdCl2(NCMe)2] gives the dinuclear complex [Pd2(μ-Cl)2(κ2-2-C6F4PPh2)2] (11), which dimerizes in solution to the tetranuclear complex [Pd4(μ-Cl)4(μ-2-C6F4PPh2)4] (12) as a result of opening of the chelate 2-C6F4PPh2 rings. Carbon monoxide inserts into a nickel−carbon σ-bond of 3 to give, after oxidation, bis-2,2′-(diphenylphosphinoyl)octafluorobenzophenone, {2,2′-C6F4P(O)Ph2}2CO (14). The molecular structures of complexes 1−3, 6, 8, 9, and 14 have been determined by single-crystal X-ray methods.