Some Unusal Dimeric and Cluster Species of the Group VI Transition Metals

Clusters as Ligands. 4. Synthesis, Structure, and Characterization of the Tungsten(II)−Tungsten(III) Cluster Carboxylate {[Na][W2{OOCCCo3(CO)9}2(OOCCF3)4(THF)2]}2

“…Powders of both 1 ( g iso = 2.08) and 2 display broad, intense EPR signals at room temperature consistent with an oxidized W 2 center (Figure ). There are a few known examples of paramagnetic W 2 compounds in the literature (WMo(OOCBu t ) 4 I, W 2 (OOCBu t ) 4 I, CpW(CO) 2 34 ), but a W(III)−W(IV) system constitutes a useful example to compare with 1 . , The EPR signals of 1 and 2 resemble that of [W 2 (Cl)(SPh) 2 Cl 6 ] 2- 35 ( g 1 = 2.311, g 2 = 1.893, g 3 = 1.747, at RT ; Δpp ∼ 100 G). With a W 2 coordination geometry of two confacial octahedrons, a d 3 /d 2 electron configuration, and C 2 v symmetry, this compound is a reasonable model for 1 .…”

Reactions and reaction products of bromine and iodine with tetrakis(ethyl xanthato)dimolybdenum(4.degree.Mo-Mo)

“…The data were reduced to a set of relative |F0|2 values. 6 The intensities were corrected for absorption effects (µ = 62.1 cm™1); transmission coefficients ranged from 0.160 to 0.394 with an average of 0.285. The 2396 data having / > 3 (/) were retained as observed and used in subsequent structure solution and refinement.…”

“…Structure Solution and Refinement. 6 The positions of the 32 unique nonhydrogen atoms were determined by standard heavy-atom methods.…”

Preparation and characterization of dimeric and tetrameric clusters of molybdenum and tungsten

“…The quadruply bonded tungsten and molybdenum dimers undergo only a limited number of reversible oxidations. The molybdenum carboxylates, Mo2(02CR)^ may be oxidized by I2 to Mo2(02CR)^^2 in a thermally reversible reaction (60).…”