Molybdenum complexes boron

When applying these methods to the study of molybdenum complexes Voityuk and Rosch [25, 41] found that the use of the AMI core-repulsion function (Eq. 5-6) led to some systematic deviations for some Mo—X bond lengths. To address these problems, important changes to the core-repulsion function were made by the introduction of bond-specific parameters (omo-x and 8 io-x, Eq. 5-9) [22, 25], The idea of using bond-specific core repulsion parameters is not new, since the AMI parameterisation of boron used bond-specific Gaussian functions to improve the final results [42],... 

Similarly, orange-red needles (mp 53 °C) of 1-fluoroborepin molybdenum carbonyl complex 18 were obtained by conversion of 1-methoxyborepin 17 to the corresponding Mo(CO)3 complex followed by immediate treatment of the crude complex with boron trifluoride in pentane, as in Scheme 1. The intermediate molybdenum complex of 17 could be isolated as air- and moisture-sensitive crystals (mp 110-115 °C) but prolonged manipulation led to contamination by the corresponding 1-hydroxyborepin complex <19970M1884>. 

This shows that the t)rpe of product isolated is dependent on the nature of the cyclopentadienyl(alkylidyne)metal reagent used. Thus protonation of an equimolar mixture of the tungsten compoimds 2a and 3a affords 21a as the only product, whereas when the cyclopentadienyl-molybdenum complex 3d is employed with 2a, a mixture of B9 and Bio products results. On the other hand mixtures of 2a with 3b, which bears the sCMe group, yield only complex 22a upon protonation. ot) fhe overall form of the dimetal species 21 and 22 is related to the species 20, however, unlike the latter compound no CH2R boron cage substituent is observed in the products from 2a. The compoimds... 

Marcantoncetos et al. [112] have described a phosphorimetric method for the determination of traces of boron in seawater. This method is based on the observation that in the glass formed by ethyl ether containing 8% of sulfuric acid at 77 K, boric acid gives luminescent complexes with dibenzoylmethane. A 0.5 ml sample is diluted with 10 ml 96% sulfuric acid, and to 0.05-0.3 ml of this solution 0.1ml 0.04 M dibenzoylmethane in 96% sulfuric acid is added. The solution is diluted to 0.4 ml with 96% sulfuric acid, heated at 70 °C for 1 h, cooled, ethyl ether added in small portions to give a total volume of 5 ml, and the emission measured at 77 K at 508 nm, with excitation at 402 nm. At the level of 22 ng boron per ml, hundredfold excesses of 33 ionic species give errors of less than 10%. However, tungsten and molybdenum both interfere. 

In recent work, Ashe et al. have prepared a series of molybdenum tricarbonyl complexes of C6H6B-R ligands.142 X-ray diffraction data on [H6C6B-N(CHMe2)2]Mo(CO)3 123 revealed that the metal is coordinated to the six ring carbons but not to boron. 

Few examples have been reported of metals coordinated to six-membered boron-sulfur heterocycles. Ashe et al. prepared 4-methyl-l,4-thiaborin (SC4H4BMe) which forms a stable molybdenum tricarbonyl sandwich complex 144.158 jn g etjert s laboratory, the reaction of the diborolyl complex 33 (Section 3.01.3.2) with COS afforded the dinuclear complex 145 whose structure was determined crystallographically.36 Other products, not involving boron-sulfur heterocycles and hence outside the scope of this discussion, were obtained via the treatment of 33 with different sulfur reagents such as CS2.36... 

Elimination to yield alkenes can be induced thermally or by treatment with acids or bases (for one possible mechanism, see Figure 3.39) [138,206]. Less common thermal demetallations include the thermolysis of arylmethyloxy(phenyl)carbene complexes, which can lead to the formation of aryl-substituted acetophenones [276]. Further, (difluoroboroxy)carbene complexes of molybdenum, which can be prepared by treating molybdenum hexacarbonyl with an organolithium compound and then with boron trifluoride etherate at -60 °C, decompose at room temperature to yield acyl radicals [277]. 

Compound 12 displays an altogether different reactivity pattern upon treatment with iodine in the presence of an ether or a thioether. Thus, the sole product of the reaction of 12 in THF with iodine was the anionic Mo complex [N(PPh3)2][2,2,2-(CO)3-2-I-7-0(CH2)4-c/oxo-2,1-MoCBioHio] (67), with the carborane cage having undergone a substitution at a boron vertex. The substitution occurs at a p boron atom in the CBBBB face that ligates the molybdenum atom. When 67 is treated with further iodine in THF no reaction occurs. However, treatment with iodine using... 

Hunt s group (50, 51) have pioneered the application of the Cl source to organometallics such as the iron tricarbonyl complex of heptafulvene, whose electron impact spectrum shows (M—CO)+ as the heaviest ion, in contrast to the methane Cl spectrum with the ion as base peak. Boron hydrides (52) and borazine (53) have also been studied. The methane Cl spectrum of arenechromium and -molybdenum (54) show protonation at the metal giving a protonated parent or molecular ion. Risby et al. have studied the isobutane Cl mass spectra of lanthanide 2,2,6,6-tetramethylheptane-3,5-dionates[Ln(thd)3] (55) and 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-oetanedione [H(fod)] lanthanide complexes (56). These latter complexes have been suggested as a means of analysis for the lanthanide elements. 

A number of other hydride complexes have been prepared the purple, diamagnetic hydride [MoH(BH4)(PMe3)4] has been obtained by reaction of NaBH4 with [MoCl3(PMe3)3]. The essentially tram octahedral structure of this molecule has been determined by X-rays as shown in (9) the hydride, the molybdenum and the boron atom of the bidentate BH4 group lie precisely on the intersection of two mirror planes in the molecule.86... 

The lack of adequate experimental data on chelates of germanium, boron, titanium, and vanadium prevents a similar comparison for these elements however, their high ionic potentials do indicate that they should form stable chelates. Vanadium does occur naturally in the very stable vanadium porphyrin complex. For similar reasons, molybdenum and tin are not discussed further. 

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