Molybdenum cyclopentadienyl compounds

Cyclopentadienyl molybdenum-sulfur compounds are useful synthons for the preparation of Mo—M—S (e.g. M = Fe (see Section 36.6.2), Co, Ni) clusters103-108 144 in reactions with metal carbonyls. However, the principal interest in molecules of this class has arisen because of the reactivity of the Mo—S system, primarily in respect of the making and breaking of S—H... 

Comparable results were further observed when neutral cyclopentadienyl-molybdenum(II) compounds like MoCpCl(CO)3 were used as catalysts in that immobilisation of the catalyst in an ionic liquid afforded lower turnover frequencies relative to the reaction in neat substrate.[33]... 

CpMoX and Derivatives. [CPM0X4] (X = Cl, Br) are best synthesized by oxidation of [CpMoMe(CO)3] with PCI5 or PBrs. The tetrachloride may also be prepared on treatment of [CpMoO(Cl)2] with HCl. These Mo compounds may be reduced to lower valent species. Thus, treatment of [CpMoCLt] with zinc affords the insoluble molybdenum(III) compound [(CpMoCh) ]. Enhanced solubility is obtained through the use of alkylated cyclopentadienyl ring systems. The Mo complexes are best prepared by one of two methods ... 

Chromium forms a cyclopentadienyl compound similar to ferrocene (p. 499). Cyclopentadienyl sodium reacts with anhydrous chromium (I I) chloride in tetrahydrofuran to give red (C5H5)2Cr. By oxidising this, compounds containing the (C5H5)2Cr+ ion are easily obtained (Cotton and Wilkinson, 1954). When cyclopentadiene mixed with molybdenum or tungsten carbonyl is passed through a tube heated to 300 the dicyclopentadienyl hexacarbonyl is formed (Wilkinson, 1954) ... 

A wide variety of other cyclopentadienyl molybdenum-sulfur compounds are known including monomeric [Cp2Mo(SR)2], [CP2M0S2] and [CP2M0S4], dimeric... 

Fig. 4. Representative structures for compounds of molybdenum(IV) (a) bis(diaIkyldithiocarbamato)oxomolybdenum(IV), MoO(S2CNR2)2, where R = alkyl (b) / Jtetracyanodioxomolybdenum(IV), Mo02(CN) (c) M03SJ3 (d) Mo3S4(SCH2CH2 )1 (e) Mo304(H20)g" (f) the Mo M S thiocubane core stmcture (g) bis(cyclopentadienyl)dichloromolybdenum(IV), CP2M0CI2, where Cp = cyclopentadienyl.

Molecular examples of trivalent molybdenum are known in mononuclear, dinuclear, and tetranuclear complexes, as illustrated in Figure 5. The hexachloride ion, MoCk (Fig- 5a) is generated by the electrolysis of Mo(VI) in concentrated HCl. Hydrolysis of MoCP in acid gives the hexaaquamolybdenum(III) ion, Mo(H20) g, which is obtainable in solution of poorly coordinating acids, such as triflic acid (17). Several molybdenum(III) organometaUic compounds are known. These contain a single cyclopentadienyl ligand (Cp) attached to Mo (Fig. 5d) (27). 

Fig. 5. Representative structures for compounds of molybdenum(III) (a) hexacholoromolybdenum(III) ion, MoClg (b) bexabis(dimethylamiHo)dimo1ybdeniim (TTT), Mo (N(CH ) ) (c) the Mo S thiocubane core stmcture (d) dichlorocyclopentadienyl triaIkylphosphinedichloromolybdenum(III), CpMo(PR2)Cl2, where Cp = cyclopentadienyl and R = alkyl.

Fig. 7. Representive stmctures for compounds of molybdenum(0) (a) Mo(CO)g (b) tris(acetonitrile)tris(carbonyl)molybdenum(0) (c) bis(l,2-diphenylphosphinoethane) bis (dinitrogen) molybdenum(0), [R2PCH2CH2PR2]2Mo(N2)2, where R = CgH, also known as Mo(dppe)2(N2)2, where dppe = 1,2 — diphenylphosphinoethane (d) cyclopentadienyl tricarbonyl molybdenum(0) anion, CpMo(CO)3, where Cp = cyclopentadienyl (e)...

In a similar manner, Jt-allyl complexes of manganese, iron, and molybdenum carbonyls have been obtained from the corresponding metal carbonyl halides [5], In the case of the reaction of dicarbonyl(r 5-cyclopentadienyl)molybdenum bromide with allyl bromide, the c-allyl derivative is obtained in 75% yield in dichloromethane, but the Jt-allyl complex is the sole product (95%), when the reaction is conducted in a watenbenzene two-phase system. Similar solvent effects are observed in the corresponding reaction of the iron compound. As with the cobalt tetracarbonyl anion, it is... 

The spectra of the cyclopentadienyl metal halides of iron and molybdenum have been reported (212). The halide atoms are lost less readily than the CO groups, but about as readily as the Cp group. Thus for CpFe(CO)2Br, the most abundant ions are CpFeBr+, FeCp+, P+, FeBr+, and CpFe(CO)Br+. Most of the other expected ions are also found, such as FeCpJ, CpFe(CO), C3H3FeBr+, C3H3Fe+, C2HFe+, FeBr+, and Fe+. Similar results were observed for CpFe(CO)2Cl (49). The molybdenum compound shows a similar pattern. 

Bis[cyclopentadienyl]bis[arenetellurolato]molybdenum compounds were obtained as quite air-stable, brown solids from bromomagnesium arenetellurolates and bis[cyclopentadien-yl]molybdenum dichloride2. 

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