Showing papers by "Shiro Hikichi published in 2005"
TL;DR: In this article, the complexation of Dawson-type polyoxometalates with the macrocation ([Cr3O(OOCH)6(H2O)3]+) has been studied.
Abstract: The complexation of Dawson-type polyoxometalates of [α-P2W18O62]6-, [α2-P2W17V1O62]7-, and [α-P2W15V3O62]9- with the macrocation ([Cr3O(OOCH)6(H2O)3]+) forms ionic crystals of (NH4)4[Cr3O(OOCH)6(H2O)3]2[α-P2W18O62]·15H2O (1a), (NH4)5[Cr3O(OOCH)6(H2O)3]2[α2-P2W17V1O62]·15H2O (2a), and (NH4)7[Cr3O(OOCH)6(H2O)3]2[α-P2W15V3O62]·15H2O (3a), respectively. The compounds 1a−3a show the honeycomb packing and the symmetry of the constituent ions reflect on the crystal structures. The lengths of the a axes of 1a−3a are almost the same, while those of the c axes decrease in the order of 1a ≥ 2a > 3a, with the increase in the anion charges of the polyoxometalates. The water of crystallization in 1a−3a is desorbed by the evacuation at 373 K to form the respective guest-free phases 1b−3b. The compounds 1b−3b are crystalline, and the lengths of the a axes of 1b−3b are almost the same, while those of the c axes decrease in the order of 1b ≥ 2b > 3b. The compounds 1b−3b possess voids running perpendicular to the c axis. Th...
49 citations
TL;DR: Unrestricted DFT calculations for the model complexes prove that the two metal centers are held together not by covalent interactions, but by electrostatic attractions, and the obtained xenophilic complexes can be regarded as carbonylmetalates.
Abstract: A series of dinuclear complexes, [Tp(R)M--M'L(n)] [Tp(iPr(2) )M--Co(CO)(4) (1; M=Ni, Co, Fe, Mn); Tp(#)M--Co(CO)(4) (1'; M=Ni, Co); Tp(#)Ni--RuCp(CO)(2) (3')] (Tp(iPr(2) )=hydrotris(3,5-diisopropylpyrazolyl)borato; Tp(#) (Tp(Me(2),4-Br))=hydrotris(3,5-dimethyl-4-bromopyrazolyl)borato), has been prepared by treatment of the cationic complexes [Tp(iPr(2) )M(NCMe)(3)]PF(6) or the halo complexes [Tp(#)M--X] with the appropriate metalates. Spectroscopic and crystallographic characterization of 1-3' reveals that the tetrahedral, high-spin Tp(R)M fragment and the coordinatively saturated carbonyl-metal fragment (M'L(n)) are connected only by a metal-metal interaction and, thus, the dinuclear complexes belong to a unique class of xenophilic complexes. The metal-metal interaction in the xenophilic complexes is polarized, as revealed by their nu(CO) vibrations and structural features, which fall between those of reference complexes: covalently bonded species [R--M'L(n)] and ionic species [M'L(n)](-). Unrestricted DFT calculations for the model complexes [Tp(H(2) )Ni--Co(CO)(4)], [Tp(H(2) )Ni--Co(CO)(3)(PH(3))], and [Tp(H(2) )Ni--RuCp(CO)(2)] prove that the two metal centers are held together not by covalent interactions, but by electrostatic attractions. In other words, the obtained xenophilic complexes can be regarded as carbonylmetalates, in which the cationic counterpart interacts with the metal center rather than the oxygen atom of the carbonyl ligand. The xenophilic complexes show divergent reactivity dependent on the properties of donor molecules. Hard (N and O donors) and soft donors (P and C donors) attack the Tp(R)M part and the ML(n) moiety, respectively. The selectivity has been interpreted in terms of the hard-soft theory, and the reactions of the high-spin species 1-3' with singlet donor molecules should involve a spin-crossover process.
26 citations