Group VI metals hexacarbonyls

Mikulski CM, Harris N, Iaconianni FJ, et al. 1980. Group-VI metal hexacarbonyl reactions with diisopropyl methylphosphonate. Inorganic Nuclear Chemistry 16(2) 79-89. 

The ligand behavior of the arsenic-based compound 9 (Figurel3) structurally related to P4S3, is of interest in this context. It was shown that 9 reacts with group VI metal hexacarbonyls under UV irradiation to give the adducts nCH3C(CH2As)3]j M(CO)5 n (N = 1,... 

Acetyl migration occurs in the reaction of Tl(MeCOCHCOMe) with Pms Pd(PhCN)2Cl2, which yields an A-acetyl-jS-ketoimine chelate (17).471 Mossbauer data indicate that Sn(MeCOCHCOMe)2 has a trigonal pyramidal geometry with one oxygen atom from each acetylacetonate ligand in an axial position.472 The equatorial lone electron pair is both stereochemically and chemically active. Complexes in which the metal acts as the donor rather than the acceptor are formed by photolysis of Sn(MeCOCHCOMe)2 and Group VI metal hexacarbonyls in THF. The products, Sn(MeCOCHCOMe)2M(CO)5 (M = Cr, Mo, W), evidently contain tin-metal bonds. The low... 

Table 10. Products obtained from ethylene over group VI metal hexacarbonyls...

Table 1. Ethylene reactions over group VI metal hexacarbonyls O)...

On the basis of Av (C=C), the metal-olefin bond strengths appear to vary in this homologous series in the order W > Cr > Mo. This observation is in agreement with the order of the M—C force constants determined for the Group VI metal hexacarbonyls and also compares with the somewhat greater stability observed for tungsten complexes of simple monoolefins as contrasted with those of the other Group VI metals. 

The photochemical reaction of Group VI metal hexacarbonyls with mono-enes was studied several years ago, but only recently has the reaction of one of the hexacarbonyls, W(CO)s in fact, with conjugated dienes been investigated. The W(CO)6 proves to be an effective catalyst for cis trans isomerization of such dienes compounds of the type W(CO)6(diene), which must act as intermediates in such isomerizations, have been isolated and their reactions studied. Under normal conditions iron pentacarbonyl reacts with acetylene to produce a complicated mixture of products, but under irradiation in an argon matrix at — 256 °C the product is but-l-en-3-yne, complexed to the iron through the carbon-carbon triple bond only. This iron-alkyne-carbonyl compound is presumably an intermediate in the reaction under normal thermal conditions. In an argon matrix at — 256 C, iron pentacarbonyl reacts with ethylene to give Fe(CO)4(QH4). ... 

The reactions between the Group VI metal hexacarbonyls, representing relatively simple binary carbonyl complexes, and a variety of oxides is illustrative and also derives interest from the active alkene metathesis catalysts provided [20,21]. The initial interaction of Mo(C0)5 with silica has been monitored by infrared [22] and Raman [23] spectroscopies. The complex has been shown to be physisorbed in a similar environment to that adopted in a polar solvent and to have its symmetry lowered. At 44°C, in vacuo, this species is converted to a chemically bound carbonyl which itself is apparently decarbonylated. This is complete by 100 C, giving rise to an active propene metathesis catalyst [22]. Although no C-0 infrared absorptions are evident, only 3 CO groups per metal atom have been released [21], but the nature of the molybdentam in this yellow material is unclear. Some of the metal is EPR active, and this signal indicates a Mo site in an axially symmetric site, possibly square pyramidal [24]. The proportion of Mo increases to a maximum with an activation temperature of 200°C [25]. At that... 

Thus, the transformation (3.93) of hexacarbonyls of Group VI metals with azoles and their benzoanalogues (L) in THF (Solv = THF) results in complexes of the type 684 and 685 [263,264] ... 

A few derivatives are known in which the Group VI metal has been oxidized by an oxygen-containing ligand. Treatment of hexacarbonyl-molybdenum with sulfur trioxide in liquid sulfur dioxide forms pyro-sulfato(tetracarbonyl)molybdenum, Mo[0(S03)2](CO)4, as an air-stable, hygroscopic molybdenum(II) compound, which may be polymeric 141). Treatment of hexacarbonylchromium with diphenylphosphinic acid yields a number of species of varying molecular weight, formulated as (III) 142). 

Thermal or photochemical methods can be used to prepare metal carbonyl complexes from Sb(NMe2)3 715 with the Group VI hexacarbonyls, the products are formulated as Sb(NMe2)3,M(CO)5. 

The characterization of complexes immobilized on polymers was carried out by comparison of FTIR and NMR spectra of solid organometallic polymers witii compounds prepared by complexing metal hexacarbonyls with CH3CN (6,7). Relying on FTIR and NMR data complex formation of PAN nitrile groups with VI B Group metal hexacarbonyls can be envisioned as follows ... 

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