Synthesis and structural characterization of molybdenum dimers bridged by the dithiolene ligand S2C2(CF3)2

Abstract

The complex [ C~M O ( C O )~]~ (Cp = C5H5) reacts with S2C2(CF3)2 in refluxing methylcyclohexane solution to give C~(CO)~MO[~-S~C~(CF~)~]~MOCP (1). Complex 1 loses its CO ligands on photolysis in solution to give [ C~M O (~-S~C~( C F~)~) ]~ (2). Complexes 1 and 2 were characterized by l H and 19F NMR spectroscopy, elemental analysis, mass spectrometry, and X-ray diffraction techniques. Electrochemical properties of both compounds were also studied. Crystals of 1 are monoclinic of space group E 1 / m with a = 7.153 (1) A, b = 13.404 (9) A, c = 13.690 (4) A, p = 98.54 (2)O, and 2 = 2. The structure was solved and refined to R = 0.043 and R, = 0.053 by using 1895 independent reflections. The complex contains two asymmetrically bridging S2C (CF3)2 ligands, and both CO ligands are attached to the same Mo atom. The Mo-Mo distance of 3.256 (1) A suggests minimal Mo-Mo bonding. Crystals of 2 are monoclinic of space group E 1 / a with a = 13.030 (1) A, b = 17.336 (2) A, c = 10.741 (7) A, p = 93.29 (4)', and Z = 4. The structure was solved and refined to R = 0.044 and R, = 0.057 by using 2848 independent reflections. Complex 2 contains two symmetrically bridging S2Cz(CF3)2 ligands and has an Mo-Mo bond of 2.584 (1) A.

Apparent Anti-Woodward–Hoffmann Addition to a Nickel Bis(dithiolene) Complex: The Reaction Mechanism Involves Reduced, Dimetallic Intermediates

“…We can conclude here that while square-planar dithiolenes acting as ligands have been observed previously, the structure of D3 is rather unique: first, it is rare that charge-neutral dithiolene complexes are employed as ligands (it is more common that the reduced forms are used as ligands), second it is quite unexpected that this donation leads to a rapid and reversible (in solution) switch between square planar and octahedral in the complex which the dithiolene donates to. Complex D3 is isomeric (except for the charge) to the dimetallic species D1 – and D2 – that play a key role, according to our computations, in the alkene binding mechanism.…”

Sequential Construction of One, Two, or Three Dithiolene Ligands from Alkynes and Sulfur in Dinuclear Cyclopentadienyl Molybdenum Complexes

“…As expected, one of the dithiolene ligands occupies a terminal position on Mo(2) whereas the other two adopt what we term the semibridging mode of coordination, in which one sulfur atom bridges between the two metals and the other is bound only to Mo(1). This type of bonding is well established in a number of cases, especially in dimolybdenum chemistry. ,,,− Each molybdenum thus attains a square-based pyramidal CpMoS 4 coordination sphere. The structure is thus very similar to that of one isomer of the related dicarbonyl [Mo 2 (CO) 2 {μ-S 2 C 2 (CO 2 Me) 2 } 2 Cp 2 ] but with the two CO ligands replaced by a third dithiolene.…”

Phosphine-Substituted Dithiolene Complexes as Ligands: Communication between Ruthenium(II) Centers Through a Dimolybdenum Bis(dithiolene) Core

“…Cyclic voltammetry was carried out in dichloromethane solution on selected bis(dithiolene) complexes, with the results shown in Table . Complex 2a exhibits a single reversible oxidation at 0.71 V vs AgCl/Ag, followed by irreversible oxidation processes at 1.36 and 1.63 V; it also displays an irreversible reduction at − 1.09 V. Previous electrochemical studies of the bis(dithiolene) complex Mo 2 (μ-SCHCHS) 2 Cp 2 showed that it underwent a reversible oxidation at 0.23 V vs SCE; in the C 5 H 4 Me analogue, this wave moved to 0.15 V and a second irreversible oxidation was observed at 0.64 V . In the analogous Mo 2 {μ-SC(CF 3 )C(CF 3 )S} 2 Cp 2 , the oxidation wave was at higher potential (0.88 V vs SCE) and an irreversible reduction (at −1.37 V) was also observed .…”

“…In the course of these studies, we became interested in the related Mo(III) complexes Mo 2 (μ-SCR 1 CR 2 S) 2 Cp 2 , which contain two bridging dithiolene ligands. These have been known since King prepared the first example (R 1 = R 2 = CF 3 ) by the reaction of Mo 2 (CO) 6 Cp 2 with the dithiete S 2 C 2 (CF 3 ) 2 ; further clarification of this reaction, together with the X-ray structure of the product, was later provided by Miessler and co-workers . Convenient access to a wider range of compounds of this type, including the first examples containing unsymmetrical dithiolenes (R 1 ≠ R 2 ), became available by exchange of the alkene portion of the dithiolate ligands in Mo 2 (SCH 2 CHRS) 2 Cp 2 (R = H, Me) with the alkynes R 1 C⋮CR 2 (R 1 = R 2 = H; R 1 = H or Me, R 2 = Ph) .…”