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.

We have prepared a number of complexes of the type cis-MoO2L2 where L represents a hydroxypyronato or hydroxypyridinonato ligand. Both the maltol (3-hydroxy-2-methyl-4-pyrone, Hma) and kojic acid (5-hydroxy-2-hydroxymethyl-4-pyrone, Hka) complexes, cis-MoO2(ma)2 (1) and cis-MoO2(ka)2 (2), have been characterized by X-ray diffraction studies. The pyrone ligands are bound to molybdenum in a cis bidentate fashion via the deprotonated hydroxyl groups and the ketone moieties. Crystals of 1 are orthorhombic, a = 12.107 (1), b = 8.6169 (8), c = 16.472 (1) Å, Z = 4, space group Pca21, and those of 2 are monoclinic, a = 8.4591 (5), b = 16.3453 (10), c = 10.2954 (7) Å, β = 103.0320 (10)°, Z = 4, space group P21/c. Hydroxypyridinone molybdenum complexes have been prepared for both maltol and kojic acid derivatives with the substituents Me, n-Pr, CH2Ph, Ph at the ring nitrogen. Crystals of the 3-hydroxy-2-methyl-1-phenyl-4-pyridinone (Hppp) derivative, MoO2(ppp)2 (9), are monoclinic, a = 10.9476 (6), b = 13.5353 (9), c = 17.4877 (10) Å, β = 93.465 (4)°, Z = 4, space group P21/n. Initial investigations into the effects molybdenum compounds have on diabetic hearts are presented. Both Na2MoO4 (used as a control) and 1 were effective in lowering blood glucose and free fatty acid levels. Diabetic rats treated with molybdate showed significant improvements in postischemic cardiac function.Key words: molybdenum, hydroxypyrones, hydroxypyridinones, heart function.

Addition of cis-cyclooctene (coe) to K2PtCl4 gives trans-[PtCl2(coe)]2 (1), which reacts with excess coe to give trans-PtCl2(coe)2 (2). Compound 2 was characterized by an X-ray diffraction study and crystals were found to be triclinic, a = 5.7838(5), b = 7.4347(6), c = 9.9972(9) Å, α = 83.924(1), β = 87.844(2), γ = 73.546(1)°, Z = 1, with space group P1-. Addition of 4-vinylpyridine (4vp) to 1 gave trans-PtCl2(4vp)2 (5) which was also characterized by an X-ray diffraction study. Crystals of 5 were monoclinic, a = 8.2255(6), b = 12.8254(10), c = 6.9624(5) Å, β = 98.8230(10)°, Z = 2, with space group P21/c. Although alkenylamines react with 1 to give a mixture of products, addition of one equivalent of apve (H2NCH2CH2CH2OCHβCH2) to 1 cleanly afforded the organometallic product trans-PtCl2(coe)(thmo) (thmo = tetrahydro-2-methyl-1,3-oxazine) arising from a metal-catalyzed intramolecular hydroamination of the starting alkenylamine. Initial investigations into the functionalization of metal complexes containing pendant alkene groups have shown that catecholborane can be added in some cases, using a rhodium catalyst, to give the corresponding organoboronate ester platinum compounds.Key words: alkenylamines, alkenylpyridines, hydroamination, hydroboration, platinum.

Doppelschichten oder offene Leiterstruktur? Von den Kristallisationsbedingungen hängt es ab, welches supramolekulare Isomer aus Co(NO3)2 und dem konformativ beweglichen Spacer 1,2‐Bis(4‐pyridyl)‐ethan erhalten wird. Das letztgenannte Koordinationspolymer weist 10 × 10 Å große Hohlräume auf. Rechts ist ein Ausschnitt aus dem Doppelschicht‐Strukturmotiv gezeigt.

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