Supramolecular coordination compounds bear exceptional advantages over their organic counterparts. They are available in one-pot reactions and in high yields and display physical properties that are generally inaccessible with organic species. Moreover, their weak, reversible, noncovalent bonding interactions facilitate error checking and self-correction. This Review emphasizes the achievements in supramolecular coordination chemistry initiated by serendipity and their materialization based on rational design. The recognition of similarities in the synthesis of different supramolecular assemblies allows prediction of potential results in related cases. Supramolecular synthesis obeys guidelines comparable to the "lead sheet" used by small jazz ensembles for improvisation and therefore more often leads to unpredicted results. The combination of detailed symmetry considerations with the basic rules of coordination chemistry has only recently allowed for the design of rational strategies for the construction of a variety of nanosized systems with specified size and shape.

COMMUNICATIONSCarbonyl addition reactions: To a solution of the cerium compound (1.5 mmol) in T H F ( 5 mL) cooled to -78'C, methyllithium (1.2 mmol, 0.75 mL of a 1 . 6~ solution in diethyl ether) was added. After 1 h the appropriate carbonyl derivative (2.0mmol) was added slowly and the mixture was stirred at -78°C for 30 min. Then, a saturated aqueous NH,CI solution (10 mL) was added, solid material war removed through a short pad of Celite, the Celite was rinsed with diethyl ether, and the ethereal solution was dried with MgSO,. The solvent was removed in vacuo and the residue purified by llash chromatography.

The magnetic anisotropy of the two cyclic hexanuclear Fe(III) clusters [Li⊂Fe 6 L 6 ]Cl‚6CHCl 3 and [Na⊂Fe 6 L 6 ]-Cl‚6CHCl 3 , L ) N(CH 2 CH 2 O) 3 , was investigated. Based on a spin Hamiltonian formalism, the magnetic anisotropy was calculated exactly to first order, i.e., in the strong exchange limit, using Bloch's perturbational approach and irreducible tensor operator techniques. Experimentally, the magnetic anisotropy was investigated by magnetic susceptibility and high-field torque magnetometry of single crystals as well as inelastic neutron scattering. It is demonstrated that torque magnetometry provides a valuable tool for the study of magnetic anisotropy in spin cluster complexes. The experimental data could be accurately reproduced by the calculations, and the different methods yield consistent values for the coupling constants and zero-field-splitting parameters. Both the anisotropy and the exchange interaction parameter are found to increase with increasing Fe-O-Fe angle.

An Mg4 tetrahedron constitutes the center of the chelate complex anion of 1, which is obtained in 85% yield from diethyl malonate, methylmagnesium iodide, and oxalyl chloride (1:1:0.25). Acid hydrolysis of 1 affords the free chelate ligand, which is an extremely interesting synthetic building block.