NEW METAL-CARBONYL-COMPLEXES OF MIXED GROUP-15 GROUP-16 ANIONS - STRUCTURAL CHARACTERIZATION OF [FE(AS3SE3)(2)(CO)](2-),[MN(AS3SE5)(CO)(3)](2-), AND [FE-2(ASTE4)(2)(CO)(4)](2-)/

The reactions of various mixed arsenic selenides and tellurides with m etal carbonyls have been investigated. Several new clusters have been isolated and stucturally characterized, Iron carbonyl reacts with As4S e62- to form [Fe(As3Se3)(2)(CO)](2-), which contains two As3Se32- frag ments attached to an Fe(CO) center. The compound is reminiscent of (an d isoelectronic with) the previously reported [M(As3Se3)(2)(CO)(2)](2- ) (M = Mo, W). Crystallographic data: space group (P) over bar 1, a = 13.114(2) Angstrom, b = 19.250(2) Angstrom, c = 11.791(2) Angstrom, al pha = 98.85(1)degrees, beta 108.81(1)degrees, gamma = 88.86(1)degrees, V = 2782.7(7) Angstrom(3), Z = 2, R = 0.0721, R(w) = 0.0931. The same main group cage also reacts with Mn-2(CO)(10) to form [Mn(As3Se5)(CO) (3)](2-), which has a completely new topological framework. The struct ure is based on the As4Se4 type with one As vertex replaced by a Mn(CO )(3) fragment and the bound As containing a terminal As=Se bond. Cryst allographic data: space group (P) over bar 1, a = 10.298(3) Angstrom, b = 11.649(3) Angstrom, c = 24.950(6) Angstrom, alpha = 90.30(2)degree s, beta = 94.32(2)degrees, gamma = 106.35(2)degrees, V = 2863(1) Angst rom(3), Z = 2, R = 0.0464, R(w) = 0.0539. Iron carbonyl also reacts wi th As2Te62- to form the first example of a transition metal arsenic te lluride complex, [Fe-2(AsTe4)(2)(CO)(4)](2-). This dimer contains two Fe(CO)(2) fragments linked by two unusual (Te-2)AsTe-Te ligands. Cryst allographic data: space group C2/c, a = 11.268(4) Angstrom, b = 21.228 (9) Angstrom, c = 26.413(9) Angstrom, beta = 100.32(3)degrees, V = 621 6(4) Angstrom(3), Z = 4, R = 0.0646, R(w) = 0.0613. In addition to X-r ay difffraction, these compounds were characterized by IR, far-IR, and Se-77 and Te-125 NMR. A mote convenient preparation of the As2Te62- s alt is also reported.