Synthetic and Structural Studies on Linear and Macrocyclic Pd- and Pt-Bridged Butterfly Fe/S Cluster Complexes

Three
types of (diphosphine)­Pd- or Pt-bridged butterfly Fe/S cluster
complexes have been prepared by a simple and convenient one-pot synthetic
method. The first type of such complexes involves the linear (diphosphine)­Pd- or Pt-bridged double-butterfly
Fe/S clusters [(μ-RS)­(μ-SCS)­Fe2(CO)6]2[M­(diphosphine)] (1–12; M = Pd and Pt; R = Et, t-Bu, Ph, and p-MeC6H4; diphosphine = dppe, dppv,
and dppf), which were prepared by sequential reactions of monoanions
[(μ-RS)­(μ-CO)­Fe2(CO)6]– (formed in situ from Fe3(CO)12, RSH, and Et3N) with excess CS2, followed
by treatment of the resulting monoanions [(μ-RS)­(μ-SCS)­Fe2(CO)6]– with (diphosphine)­MCl2. The second type of complexes involves the macrocyclic (diphosphine)­M-bridged
double-butterfly Fe/S clusters [μ-S­(CH2)4S-μ]­[(μ-SCS)­Fe2(CO)6]2[M­(diphosphine)] (13–16;
M = Pd and Pt; diphosphine = dppe and dppv), which were prepared by
sequential reactions of dianion [{μ-S­(CH2)4S-μ}­{(μ-CO)­Fe2(CO)6}2]2– (generated in situ from Fe3(CO)12, dithiol HS­(CH2)4SH,
and Et3N) with excess CS2, followed by treatment
of the resultant dianion [{μ-S­(CH2)4S-μ}­{(μ-SCS)­Fe2(CO)6}2]2– with (diphosphine)­MCl2. In contrast, when dithiol HS­(CH2)4SH was replaced by HS­(CH2)3SH (a dithiol with a shorter carbon chain), the aforementioned sequential
reactions afforded the third type of macrocyclic complexes which involves
the (diphosphine)­M-bridged quadruple-butterfly Fe/S clusters [{μ-S­(CH2)3S-μ}­{(μ-SCS)­Fe2(CO)6}2]2[M­(diphosphine)]2 (17–20; M = Pd and Pt; diphosphine
= dppe and dppv). While the two possible pathways are suggested for
production of the two types of novel macrocyclic Fe/S clusters 13–20, respectively, all new complexes 1–20 have been characterized by elemental
analysis, spectroscopy, and, for some of them particularly, DFT calculations
and X-ray crystallography.