Reaction of CpW(CO)₂(μ-PPh₂)Mo(CO)₅ and Fe₂(μ-S₂)(CO)₆:  Unusual Fragmentation and Coordination of Fe₂(μ-S₂)(CO)₆

Abstract

Reaction of Fe2(μ-S2)(CO)6 with at dichloromethane reflux afforded heterotrimetallic clusters CpW(μ-PPh2)Mo(CO)3(μ-CO)(μ3-S)2Fe2(CO)5 (1), Cp(CO)W(μ-PPh2)Mo(CO)3(μ3-S)2Fe(CO)3 (2), CpW(μ-PPh2)Mo(CO)3(μ3-S)2Fe2(μ-CO)(CO)4 (3), and CpW(CO)(μ3-S)2Fe(μ-PPh2)Fe(CO)4Mo(μ3-S)2Fe2(CO)6 (4). Thermolysis of 1 in dichloromethane produced 3, which was also obtained by the reaction of 2 with Fe2(CO)9 at dichloromethane reflux. Reflux of a benzene solution of 3 with norbornadiene (nbd) produced CpW(μ-PPh2)Mo(CO)(nbd)(μ3-S)2Fe2(μ-CO)(CO)4 (5), but the typical reaction without nbd afforded a benzene substitution product, CpW(μ-PPh2)Mo(η6-C6H6)(μ3-S)2Fe2(μ-CO)(CO)4 (6). Molecular structures of 1−6 were determined by single-crystal X-ray diffraction analyses. Cluster 1 has bitetrahedral geometry, where the Fe2MoW core is intercepted by an Fe−W bond to FeMoW and Fe2W units, and each unit is capped by a μ3-S atom. Cluster 2 is a rare example of square pyramidal geometry with the FeS2W plane capped by a Mo atom, whereas cluster 3 consists of an Fe2MoW tetrahedron core with each FeMoW face capped by a μ3-S atom. Clusters 4−6 possess an Fe2MoW core geometry similar to that of 3, where carbonyl ligands on the Mo site were replaced by Fe2(μ-S2)(CO)6, nbd, and benzene, respectively.

Activation of the S−S Bonds of Alkyl Disulfides RSSR (R = Me, Et, Pr, Bun) by Heterodinuclear Phosphido-Bridged CpW(CO)2(μ-PPh2)Mo(CO)5

“…A facile activation of the S−S bonds of RSSR (R = Ph, p -MeC 6 H 4 ) by the reactive heterodinuclear complex ( 1 ) and formation of the 34e dimers (R = Ph ( 2a ), p -MeC 6 H 4 ( 2b )) and the 32e dimers (R = Ph ( 3a ), p -MeC 6 H 4 ( 3b )) were reported earlier 5a. According to the 18e rule, a double bond should exist between the Mo and W atoms in the 32e dimer 3a .…”

“…According to the 18e rule, a double bond should exist between the Mo and W atoms in the 32e dimer 3a . However, the actual Mo−W bond distance (2.8589(6) Å) in 3a is not only considerably longer than the reported MoW double-bond distance (2.702−2.718 Å) 6 but also longer compared to that of the 34e dimer 2a (2.8427(14) Å) 5a. To verify whether such a trend is general in other 34e and 32e dimers, and to explore whether the electronic or steric effects dominate, we have prepared a series of new 34e and 32e dimers by preparing them by reactions of alkyl disulfides RSSR (with R = Me, Et, Pr, Bu n ) with the heterodinuclear phosphido-bridged complex 1 , under mild conditions.…”

“…This is the most likely configuration, as the complexes 6a − d are already overcrowded by the SR and PPh 2 bridges. Formation of the complexes 6a − d was not observed during reactions between 1 and aryl disulfides ArSSAr (Ar = Ph, p -MeC 6 H 4 ) under identical conditions 5a. This indicates the lack of availability of the PPh 2 SAr ligands for complexation.…”

“…Furthermore, the versatility of the phosphido groups is shown by the reversible uptake of a hydrogen atom to form a terminal phosphine and the possibility of reversible P−C bond cleavage . These transformations, flexibility, and versatility of the bridging PPh 2 ligand are known, including a recent report of the interaction of a bridging PPh 2 ligand with a benzene radical to yield a PPh 3 ligand 5a. The formation of the PPh 2 SR ligands via interaction of the bridging PPh 2 ligand and the SR fragments (from RSSR) is the subject of this paper.…”

Formation of a Dithiophosphinate Ligand Ph2PS2 by Sulfur Insertion into the Metal−Phosphido Bond on Heterobimetallic Phosphido-Bridged Complex Cp(CO)2W(μ-PPh2)Mo(CO)5: A Rare Example of a Neutral Six-Electron Mixed-Metal Cluster with a Mo2WS4 Core

“…We have reported that the phosphido-bridged heterodinuclear complex ( 1) , which has a reactive metal−metal bond and labile carbonyl ligands for further reaction, is a suitable precursor for oxidative addition of both organic disulfides RSSR (R = alkyl or aryl group) and inorganic disulfide (Fe 2 (μ-S 2 )(CO) 6 ) via the S−S bond cleavage. Formation of a hybrid ligand Ph 2 PSR by interaction between phosphido-bridged PPh 2 on 1 and SR during RSSR activation and the S(p π ) → Mo(d) ligand-to-metal dative π-bonding interactions in the complexes where SR is a terminal ligand have also been reported …”