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The molecular structure of [Cp*2Mo2P2S3] (1; Cp* = η5-C5Me5) has been reinvestigated. In DFT studies a series of various positional isomers A−E have been calculated for the model complex [(C5H5)2Mo2P2S3]. The energetically favored isomer [Cp*2Mo2(μ,η2:2-PS)2(μ-S)] (1B) reacts with W(CO)5THF to give [Cp*2Mo2P2S3·W(CO)5] (2). X-ray diffraction analysis of 2 confirms the presence of two η2:2-PS dumbbells and one singly bridging sulfur ligand, the W(CO)5 fragment being coordinated at one of the P atoms. Arrangement B is also found in the structure of the diadduct [Cp°2Mo2P2S3{W(CO)5}2] (3; Cp° = t-BuMe2C5H2), which is more stable than its Cp* analogue. 31P solid-state MAS NMR spectroscopic studies of 1 and 2 confirm the existence of only one isomer, but reveal disorder phenomena in the solid state within the cyclo-P2S3 middle deck. Addition of excess W(CO)5THF to 1 proceeds via elusive [Cp*2Mo2P2S3{W(CO)5}2] to give the cluster [{Cp*2Mo2W(CO)3(μ2,η2:2-PS)(μ3,η1:1:2-PS)(μ3-S)}{W(CO)5}2] (5). The molecular stru...

SamariumIII monoalkoxides bearing two, one, or no cyclopentadienyl type spectator ligands are easily synthesized by monoelectronic oxidation with tert-butylperoxide of the corresponding samariumII precursors. These monoalkoxides are single-site initiators for ring-opening polymerization.

2,2,4,4,6,6,8,8-Octamethyl-1,5-dioxo-2,4,6,8-tetrasila-3,7-exo-dimethylenecyclooctane (1) (whose X-ray structure has been determined) is a good model to study the reactivity of an exocyclic vinyl bond at silicon with styrene occurring in the presence of RuHCl(CO)(PPh3)3 (I). Two products are formed initially: the linear 2 by ring opening of 1 and the cyclic 3 by condensation with evolution of ethylene. In the presence of an excess of styrene, 2 undergoes consecutive reactions giving subsequent styryl derivatives. Effective catalysis by I and the lack of activity of Ru−carbenes (II) for the reaction were examined. An MS study of the products (2D and 3D) of the reaction of deuterated styrene with 1 provides convincing evidence for a mechanism that does not involve a metallacarbene. A sequential insertion−elimination mechanism is proposed for the catalytic process.

The complex Cp‘2Ta(H)(OCOCF3)2 (2) is synthesized by the acidolysis of Cp‘2TaH3 (1) (Cp‘ = η5-tBuC5H4) in the presence of an excess of trifluoroacetic acid. 1 undergoes a loss of H- upon the reacti...

Two kinds of ansa derivatives, [SiMe2(η5-C5H4)2]MCl2 and [CMe2(η5-C5H4)2]MCl2 (M = Mo, W), are reacted with metallophosphide anions [PPh2M‘(CO)x]- (M‘ = Cr, Mo, W, x = 5; M‘ = Fe, x = 4). The silicon-bridged derivatives give the bimetallic systems [SiMe2(η5-C5H4)(η5-C5H3PPh2M‘(CO)x)]M(H)(Cl), which result from a regioselective substitution at the 3-position on the cyclopentadienyl ligand. In contrast, with the CMe2-bridged compounds, the substitution reaction occurs at the metallic center, giving μ-phosphido bimetallic complexes [CMe2(η5-C5H4)2]M(Cl)(μ-PPh2)M‘(CO)x. The solid-state structure of the bimetallic complex [CMe2(η5-C5H4)2]W(Cl)(μ-PPh2)Fe(CO)4 (7d) is reported.

Reaction of the racemic metallophosphine Cp‘CpTa(CO)(PMe2) (1; Cp‘ = 1-tBu-3,4-Me2-C5H2) with the tungsten fragment [W(CO)5] affords the corresponding μ-bimetallic phosphido complex 2, which in a photochemical transformation gives the dibridged derivative Cp‘CpTa(μ-CO)(μ-PMe2)W(CO)4 (3). Addition of an optically active phosphine (PAMP) to 3 leads to a pair of optically active diastereoisomers (4a and 4b) which can be separated by fractionnal crystallization. Both diastereoisomers 4a and 4b crystallize in the orthorhombic noncentrosymmetric space group P212121. X-ray structure determinations of 4a and 4b allowed the assignment of absolute configurations of the tantalum chiral centers (S for 4a and R for 4b). The absolute configuration of the phosphorus atom of the PAMP ligand is the same (S) in both structures.