That the architecture of coordination polymers can be reasonably well predicted rests upon the simple premise that the Coordination geometry of metals can be propagated with rigid bridging ligands ("spacers"). It is therefore unsurprising that a wide range of one-,[" and three-dimensional[31 infinite frameworks have already been generated with simple, linear spacers such as 4,4'-bipyridine (1). However, that the issue of isomerism and its manifestation upon structure and bulk properties has not yet been addressed is perhaps surprising. Exploitation of spacers with conformational freedom, which are expected to engender supramolecular isomerism in the coordination polymer because of conformational isomerism, ["] has until recently remained largely unexplored.[" Here we report the dramatic effect on network morphology that conformational freedom in a ligand can impart to a coordination polymer. The architecture of the coordination polymers obtained from complexation of Co(NO,), with 1 is limited by meta1:ligand stoichiometry and thus far includes simple chains (1 :I),", ' I ladders (1 :1.5),[2",'1 and grids (1 :2).[2h-d,71 The latter two motifs can be regarded as polymeric forms of "molecular boxes" ['] and possess square, hydrophobic cavities (effective area about 8 x 8 A), which enclathrate up to four guest organic molecules.[" We anticipated that the extended spacer 2 would generate analogues with enhanced cavity size. However, reaction of Co(N0,);6H20 with 2 in solutions of MeOH/MeCN, MeOH! MeCN/ferrocene, and MeOH/CHCI, afforded three isomeric forms of [Co(N0,),(2),,,],, (3a-c, respectively).Complexes 3a-c have identical molecular formulas and asymmetric units; however, the conformational freedom of 2 manifests itself by sustaining three entirely different network structures. X-ray structural revealed statistically identical heptacoordinate environments at the Co" centers (Figure 1). The three pyridyl moieties form a "T-shaped" or meridional arrangerncnt at the metal atom; the remaining coordina- plane. b) Illustration of a single molecular hilayer of 3b and the channel5 of solvent (green. space-filling rcpresentalion) that run through the structure.
COMMUNICATIONSnoteworthy that broad bands in the range from 175 to 185 cm-' in Raman experiments on liquid iodine have been attributed to the presence of (12)n molecular clusters.[161 Our investigations on iodine insertion compounds prepared by topotactical reactions show that by restricting the geometrical arrangement of the iodine molecules, the electronic properties of the guest species can be engineered. Experimental ProcedureSyntheses of the porosils TON, FER, and MFI were performed according to the litsrature [17]. A new procedure was developed for DDR: A mixture of hydrofluoric acid, water. ammonium fluoride, I-aminoadamantane, and SiO, (Cab-osil M-5, Fluka)in themolar ratio0.15:20.1:0.15:1 wasmaintainedat433 K for21 daysin a Teflon-lined autoclabe. After the mixture had been cooled to room temperature, the crystalline product was filtered off, freed from amorphous gel residues by treatment with Zci NaOH, and washed neutral with H,O. The organic molecules occluded inside the porosils were removed by calcination in air. For that purpose, the porosils are heated to the final calcination temperature (DDR, TON, FER-1123 K, MFI: 923 K) over two days. kept at this temperature for another two days and then cooled to room temperature within one day. Insertion of iodine was performed in the \apor phase at 433 K in Teflon-lined autoclaves. After a reaction time of four days. iodine-porosil compounds were obtained. from which iodine desorbed above 313 K. At room temperature. they are srable for several weeks UV/Vis spectra in diffuse reflection were obtained on a Beckmann spectrometer model DK-2A. Quartz powder was used as a reference and for dilution of the samples. Raman spectra were recorded with an FT-Raman apparatus (Nicole1 FT-Raman 910); thc 1064 nm line of a Nd:YAG laser was used for excitation. For each measurement 200 scans were accumulated; the laser power was 200 mW for the insertion compounds. and 20 mW for bulk iodine.
A series of Lewis acid-base adducts of phosphines with amines or pyridines have been prepared and structurally characterized, demonstrating the importance of Lewis acceptor behavior in the chemistry of electron-rich (lone-pair-bearing) centers. The neutral and cationic complexes all contain examples of N-P coordinate bonds that are void of N-P pi-bonding and therefore represent definitive N-P single bonds. The structures are examples of N-P topologies that are rare or have not previously been observed, highlighting the synthetic viability of Lewis acid-base coupling in the still developing field of nitrogen-phosphorus chemistry.
Systematic NMR studies of (dialkyl/diaryl)chlorophosphine−gallium chloride reaction mixtures reveal three structural alternatives, which are related by equilibria in solution, and their relative stability is dependent on the nature of the substituent (R = Me, Et, iPr, tBu, Ph) and the reaction stoichiometry. The coordination complex R2(Cl)P→GaCl3 is observed in all cases, and a derivative (R = iPr) has been crystallographically characterized. Tetrachlorogallate salts of the diphosphorus cations [R2(Cl)P−PR2]+ are observed for smaller R substituents (R = Me, Et, iPr, Ph), consistent with a previous report. Solid-state 31P CP-MAS NMR spectra distinguish the methyl derivative from the novel salt [Me2(Cl)P−P(Me2)−GaCl3][GaCl4], containing a phosphine−phosphenium−gallium chloride cation, which has been crystallographically characterized. Factors governing the relative stabilities of the structural alternatives are discussed, and comparisons are made between the isomeric forms for R2(Cl)P:GaCl3.
Structural characterization of complexes involving neutral ligands (quinuclidine and tetramethylethylenediamine) coordinated to a neutrat phosphorus system shows unusually long ( > 2.00 A) N -+ P coordinative bonds; the bidentate ligand links two phosphorus acceptors.
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