ANTIFERROMAGNETIC COMPLEXES WITH METAL METAL BONDS .26. SYNTHESIS, MOLECULAR-STRUCTURE AND MAGNETIC-PROPERTIES OF MIXED-METAL TRIANGULAR CLUSTERS, CP2CR2(MU-SR)(MU-3-S)2FECP (R = CME3 OR PH), AND LINEAR MIXED-METAL CHAIN CPCR(MU-SPH)3FE(MU-SPH)3CRCP

The antiferromagnetic triangular cluster Cp2Cr2(mu-SCMe3)(mu3-S)2 FeCp (II) (-2J = 520 cm-1) with a strongly bonded Cr2 Fe metal core (Cr-Cr 2.650(3), Cr-Fe 2.666(3) and 2.675(2) angstrom) was obtained by prolonged photochemical reaction of Cp2Cr2(mu-SCMe3)2(mu-S) (I) and Cp2Fe2(CO)4 in THF. It was shown that thermal reaction between complex I and Cp2Fe2(CO)2(mu-SPh)2 yields two clusters, diamagnetic triangular CP2Cr2(mu-SPh)(mu3-S)2FeCp (III) and antiferromagnetic metal chain CpCr(mu-SPh)3Fe(mu-SPh)3CrCP (IV) (mu(eff). 5.29 (296 K) - 3.95 (77 K) mu(B). Complex III as well as II involves the strongly bonded metal core Cr2Fe (Cr-Cr 2.637(3), Cr-Fe 2.644(3) and 2.672(3) angstrom), whereas the Fe-Cr bonds in the linear chain of IV are considerably elongated (up to 2.996(3) and 2.969(3) angstrom), which is in agreement with their reduced bond order (equal to 1/2).