CLUSTER SYNTHESIS VIA AGGREGATION - SYNTHESIS AND SOLUTION AND SOLID-STATE CHARACTERIZATION OF SULFUR-CAPPED GROUP-6 METAL-CARBONYL CLUSTERS
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The trinuclear clusters [PPN]2[M3(CO)12S] (M = Cr, Mo, W) have been prepared by a stepwise aggregation of [M(CO)5] fragments about a sulfur atom template, with subsequent loss of three carbonyl ligands concomitant with the formation of three metal-metal bonds. The stepwise assembly process allows for the synthesis of the mixed-metal clusters [PPN]2[Cr2W(CO)12S], [PPN]2[Mo2W(CO)12S], and [PPN]2[CrMoW(CO)12S]. These compounds have been characterized by infrared and 13C NMR spectroscopies, and X-ray crystal structures of the Cr3, Mo3, and Mo2W clusters have been determined. [PPN]2[Cr3(CO)12S]: space group P21/c, a = 25.732 (6) , b = 14.255 (5) , c = 21.689 (4) , = 96.16 (3), V= 7909.8 3, Z = 4. [PPN]2-[Mo3(CO)12S]: space group P21/c, a = 25.953 (4) , b = 14.329 (2) , c = 21.830 (5) , = 96.26 (2), V = 8069.2 3, Z = 4. [PPN]2[Mo2W(CO)12S]: space group P21/c, a = 25.912 (6) , b = 14.275 (3) , c = 21.871 (3) , = 96.23 (2), V = 8042.0 3, Z = 4. The trinuclear clusters can add a fourth [M(CO)5] unit to produce the tetranuclear derivatives [PPN]2-[M4(CO)17S]. In solution, the carbonyl ligands of both the tri-and tetranuclear clusters are extremely fluxional. Temperatures as low as -110 C must be achieved to freeze out the various processes. 1988, American Chemical Society. All rights reserved.
