The nine-membered [-Cu(II)-N-N-](3) ring of trimeric copper-pyrazolato complexes provides a sturdy framework on which water is twice deprotonated in consecutive steps, forming mu(3)-OH and mu(3)-O species. In the presence of excess chlorides the mu(3)-O(H) ligand is replaced by two mu(3)-Cl ions. The interconversion of mu(3)-OH and mu(3)-O and the exchange of mu(3)-O(H) and mu(3)-Cl are reversible, and the three species involved have been structurally characterized: [PPN][Cu(3)(mu(3)-OH)(mu-pz)(3)Cl(3)(thf)].CH(2)Cl(2) (1a), monoclinic P2(1)/n, a = 10.055(2) A, b = 35.428(5) A, c = 15.153(2) A, beta = 93.802(3) degrees, V = 5386(1) A(3), Z = 4; [Bu(4)N][Cu(3)(mu(3)-OH)(mu-pz)(3)Cl(3)] (1b), triclinic P-1, a = 9.135(2) A, b = 13.631(2) A, c = 14.510(2) A, alpha = 67.393(2) degrees, beta = 87.979(2) degrees, gamma = 80.268(3) degrees, V = 1643.2(4) A(3), Z = 2; [PPN](2)[Cu(3)(mu(3)-O)(mu-pz)(3)Cl(3)] (2), monoclinic P2/c, a = 12.807(2) A, b = 13.093(2) A, c = 23.139(4) A, beta = 105.391(3) degrees, V = 3741(1) A(3), Z = 2; [PPN](2)[Cu(3)(mu(3)-Cl)(2)(mu-pz)(3)Cl(3)].0.75H(2)O.0.5CH(2)Cl(2) (3a), triclinic P-1, a = 14.042(2) A, b = 23.978(4) A, c = 25.195(4) A, alpha = 76.796(3) degrees, beta = 79.506(3) degrees, gamma = 77.629(3) degrees, V = 7988(2) A(3), Z = 4; [Bu(4)N](2)[Cu(3)(mu(3)-Cl)(2)(mu-pz)(3)Cl(3)] (3b), monoclinic C2/c, a = 17.220(2) A, b = 15.606(2) A, c = 20.133(2) A, beta = 103.057(2) degrees, V = 5270(1) A(3), Z = 4; [Et(3)NH][Cu(3)(mu(3)-OH)(mu-pz)(3)Cl(3)(pzH)] (4), triclinic P-1, a = 11.498(2) A, b = 11.499(2) A, c = 12.186(2) A, alpha = 66.475(3) degrees, beta = 64.279(3) degrees, gamma = 80.183(3) degrees, V = 1331.0(5) A(3), Z = 2. Magnetic susceptibility measurements show that the three copper centers of 2 are strongly antiferromagnetically coupled with J(Cu-Cu) = -500 cm(-1).

HO"' O OAcBielschowskysin is a naturaiiy occurring diterpene isoiated from the Caribbean gorgonian octocorai Pseudopterogorgia kallos. Its highly oxygenated hexacyclic structure is based on a previously undescribed tricyclo[9.3.0.0^'^°]tetradecane ring system that was established through spectroscopic analysis and X-ray crystallographic analysis. Bielschowskysin was shown to exhibit antimalarial activity against Plasmodium falciparum as well as strong anticancer activity against two human cancer cell lines.West Indian gorgonian octocorals (sea whips, sea feathers, sea plumes, and sea fans) are a prolific source of new terpenoids with diverse structures that often have interesting biological activities.^ For instance, the gorgonian coral Erythropodium caribaeorum is a rich source of eleutherobin and a number of analogues that are microtubule-stabilizing antimitotic agents.^ Another group of diterpene glycosides from Pseudopterogorgia elisabethae, the pseudopterosins and ieco-pseudopterosins, possesses antiinflammatory and analgesic properties that exceed the potencies of existing drugs such as indomethacin.^ Because of their unique structural features, biosynthesis, and biological activities, these families of potential drug leads have attracted much attention, thus spawning a large amount of effort directed toward their total synthesis. Despite the great interest in gorgonian corals belonging to the genus Pseudopterogorgia, these animals have not been thoroughly investigated for natural products.' In the course of our continuing investigations into the natural products chemistry of marine invertebrates from the West Indian region, we have studied extracts of Pseudopterogorgia kallos (Bielschowsky, 1918) collected near Old Providence Island located in the Southwestern Caribbean Sea.'* Previously, we have reported on two diterpenoid lactones from

A one-pot synthetic procedure yields the octanuclear Fe(III) complexes Fe(8)(micro(4-)O)(4)(micro-pz(*))(12)X(40, where X = Cl and pz(*) = pyrazolate anion (pz = C(3)H(3)N(2)-) (1), 4-Cl-pz (2), and 4-Me-pz (3) or X = Br and pz(*) = pz (4). The crystal structures of complexes 1-4, determined by X-ray diffraction, show an Fe(4)O(4)-cubane core encapsulated in a shell composed of four interwoven Fe(micro-pz(*))(3)X units. Complexes 1-4 have been characterized by 1H NMR, infrared, and Raman spectroscopies. Mössbauer spectroscopic analysis distinguishes the cubane and outer Fe(III) centers by their different isomer shift and quadrupole splitting values. Electrochemical analyses by cyclic voltammetry show four consecutive, closely spaced, reversible reduction processes for each of the four complexes. Magnetic susceptibility studies, corroborated by density functional theory calculations, reveal weak antiferromagnetic coupling among the four cubane Fe centers and strong antiferromagnetic coupling between cubane and outer Fe atoms of 1. The structural similarity between the antiferromagnetic Fe(8)(micro(4-)O)(4) core of 1-4 and the antiferromagnetic units contained in the minerals ferrihydrite and maghemite is demonstrated by X-ray and Mössbauer data.

A comparison is made between the structural, spectroscopic, electrochemical, and magnetic properties of pyrazolate versus carboxylate complexes [Fe3(μ3(μ3O)(μ-LL)6Cl3]2− containing the Fe3(μ3-O)-motif. While the Fe3(μ3-O)-cores are structurally indistinguishable in the two types of complexes, their magnetic properties deviate from the expected values as a result of a through-pyrazole contribution to the overall antiferromagnetic exchange with J 1/hc = −80.1 cm−1 and J 2/hc = −72.4 cm−1, or J 1/hc = 70.6 cm−1 and J 2/hc = −80.8 cm−1, (H ex = −J 1(S 1 S 2 + S 2 S 3) − J 2 S 1 S 3). The magnetic properties of the pyrazolate complexes are further tuned by an antisymmetric exchange interaction term.