Syntheses, Structures, FAB Mass Spectra, and Magnetic Properties of Chromium Chalcogenide Cluster Complexes [Cr6Se8(PEt3)6], [Cr6Se8(H)(PEt3)6], and [Cr6S8(H)(PEt3)6]

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Abstract
Chromium selenide cluster complexes [Cr(6)Se(8)(PEt(3))(6)] (1) and [Cr(6)Se(8)(H)(PEt(3))(6)] (2) were prepared by the reaction of anhydrous chromium dichloride, Na(2)Se(x)(), and triethylphosphine in methanol. A similar procedure except for the use of NaS(x)()H in place of Na(2)Se(x)() gave a sulfide cluster complex [Cr(6)S(8)(H)(PEt(3))(6)] (3). The partly deuterated derivative [Cr(6)S(8)(D)(0.8)(H)(0.2)(PEt(3))(6)] (4) was prepared for comparison. An extra hydrogen atom in 2-4 has been confirmed by FAB mass spectra. The reactivity and structural studies have indicated that it is at the center of the Cr(6) octahedral cluster. The molecular structures of 1 and 2 have been determined by X-ray structure analyses. Crystallographic data: [Cr(6)Se(8)(PEt(3))(6)] (1) (226 K), triclinic, P&onemacr;, a = 12.887(2) Å, b = 25.332(7) Å, c = 12.061(3) Å, alpha = 111.23(2) degrees, beta = 108.25(2) degrees, gamma = 109.86(2) degrees, Z = 2; [Cr(6)Se(8)(H)(PEt(3))(6)].2THF (2) (293 K), rhombohedral, R&thremacr;, a = 17.384(4) Å, c = 19.768(4) Å, Z = 3. The Cr-Cr bond distances of 2 are 0.13-0.16 Å shorter than those of 1, indicative of bonding interaction between the insterstitial hydrogen and the six chromium atoms in 2. The number of cluster valence electrons for 1 is 20 while that for 2 and 3 is 21. Magnetic measurements (2-330 K for 1, 2.5-330 K for 2, and 4.5-330 K for 3) have shown that the number of unpaired spins in the ground state for 1 is zero while that for 2 and 3 is one.

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