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BACKGROUND Depletion of haptoglobin (Hp) and hemopexin (Hx) with increase in free hemoglobin and heme are important etiologies of vaso-occlusive complications in sickle cell disease (SCD). This study is the first to show an association between clinical improvement in SCD and repletion of Hp and Hx by therapeutic plasma exchange (TPE) using plasma replacement. STUDY DESIGN AND METHODS Thirteen fresh-frozen plasma (FFP) units derived from consecutive whole blood donations were thawed at 37°C after 10 months of storage; Hp and Hx concentrations immediately postthaw and after 5 days of refrigerated storage were analyzed by enzyme-linked immunosorbent assay (ELISA). All SCD patients presenting to a single institution over a 2-year period with acute multiorgan failure syndrome resistant to red blood cell exchange (RCE) were treated with TPE with FFP replacement; concentrations of Hp, Hx, and heme were evaluated before and after TPE by ELISA. RESULTS Plasma concentrations of Hp and Hx decreased approximately 20% (p ≤ 0.002) after 5 days of refrigerated storage. Significant mean fold increases after TPE of 10 for Hp (p

A “second-generation” scorpionate ligand was utilized to prepare the nickel(II) borohydride complex [(TpPh,Me)Ni(η3-BH4)], wherein the borohydride was coordinated through two bridging B–H bonds, leaving two terminal B–H bonds uncoordinated as determined by X-ray crystallography. The distorted square-pyramidal complex is paramagnetic (S = 1), with 18 valence electrons, and contrasts with a previously reported 20-electron pseudo-octahedral “first-generation” analogue, [(TpMe,Me)Ni(η4-BH4)] (P. J. Desrochers, et al. Inorg. Chem. 2003, 42, 7945–7950). These distinct borohydride coordination modes were distinguished by FTIR spectroscopy, and rationalized by DFT calculations on simplified models, [(Tp)Ni(ηn-BH4)] (n = 3, 4). The difference in borohydride hapticities is attributed to the steric effect of the scorpionate 3-pyrazole phenyl substituents disposed proximally to the metal, thus demonstrating the subtle versatility of Trofimenko's scorpionate ligands in controlling ligand field geometries. The precursor complex [(TpPh,Me)Ni(κ2-NO3)] was also prepared and characterized.

Pseudotetrahedral scorpionato halide complexes [(TpPh,Me)Ni–X] [TpPh,Me = hydrotris(3-phenyl-5-methyl-1-pyrazolyl)borate] were synthesized by metathesis of Tl(TpPh,Me) and NiX2 (X = Cl, Br, I). Pyrazole adducts [(TpPh,Me)Ni(HpzPh,Me)(X)] (X = Cl, I) were also obtained. [(TpPh,Me)Ni–X] (X = Br, I) are isomorphous with previously reported [(TpPh,Me)Ni–Cl], and a new solvated pseudo-polymorph [(TpPh,Me)Ni–Cl]·2CH2Cl2 was found in this work. Ni–X bond lengths correspond to ionic radii of the halide ions, but some variations in Ni–Cl and Ni–N bond lengths are respectively attributed to bending of the chloride from the ideal threefold HB···Ni axis and to the size of the 3-pyrazole substituents. Electronic spectra were rationalized by means of time-dependent (TD) DFT calculations on simplified C3v-symmetric [(Tp)Ni–X] models. Exogenous pyrazole binds to give the pentacoordinate adducts [(TpPh,Me)Ni(HpzPh,Me)(X)] (X = Cl, I). We obtained a crystal structure of the iodide adduct, as well as that of [(TpPh,Me)Ni(HpzPh,Me)(Cl)]·0.5MeCN, isomorphous with a previously reported aquo monosolvate. A hallmark of adduct formation is an intramolecular N–H···X hydrogen bond between the added pyrazole and the adjacent halide ligand, thus giving rise to a strong IR absorption band. The stretching frequency correlates to the N(H)···X separation for the range of known adducts.