Molybdenum benzene tricarbonyl

Cycloheptatrienemolybdenum tricarbonyl has been prepared by refluxing cycloheptatriene with molybdenum hexacarbonyl in benzene. It is a convenient starting material for the preparation of trisubstituted molybdenum carbonyls and of tropyliummolybdenum carbonyl salts. ... 

Detailed vibrational assignments have been carried out on arene chromium and arene molybdenum tricarbonyl complexes (18, 19). Splitting of the E band in the carbonyl region was observed for substituted benzene chromium tricarbonyl complexes but not in (CgHg)Cr(CO)3 itself, showing that the concept of local symmetry (Cg ) is of very restricted validity when discussing the C—O stretching vibrations in such complexes (18). 

Arene tricarbonyl molybdenum complexes are yellow, often crystalhne compounds. They are weakly air-sensitive in the sohd state and have to be stored under inert atmosphere and out of hght. They are best purified by crystaUization. In solution, they are unstable to air. The trait that has most hampered development of the use of (arene)Mo(CO)3 complexes in organic synthesis, however, is the lability of the arene metal bond. Lewis basic solvents such as THF, DMF, DM-SO, acetone and acetonitrile rapidly displace benzene in (benzene)Mo(CO)3. This lability of the arene-Mo bond, while making handling difficult, holds promise for the catalytic use of this class of compounds. 

These reactions are extremely sensitive to conditions, e.g., temperature, solvent, etc. The best one is the reaction of the palladium complex (XXXVII) with iron pentacarbonyl to give (XIII). At 80° C the yield ranges from 87% in benzene, cyclohexane, or 1,2-dichloroethane, to 17% in tetrahydro-furan-diglyme and is zero in carbon tetrachloride (77). The reaction of (XXXVII) with molybdenum hexacarbonyl only occurs in aromatic hydrocarbon solvents and since the complex (XL) is obtained in the same yield starting from either molybdenum hexacarbonyl or benzenemolyb-denum tricarbonyl, it is reasonable to assume the latter to be an intermediate in this reaction. 

Some reports of failures to obtain cyclobutadiene complexes have also appeared (10,40). Chatt et al. (21) also noted that biphenylene (II) was very reluctant to form a metal complex. The only ones which could be made were molybdenum tricarbonyl complexes where the Mo(CO)3 group was bonded to the benzene, rather than to the four-membered ring. 

C1BH12M0S6, Tris(benzene-1,2-dithiolato)molybdenum(VI), 42B, 942 ClbHi2N2PdS2, Bis(8"mercaptoquinolinato)palladium, 39B, 824 ClbHi2N2PtS2 f Bis(8-mercaptoquinolinato)platinum, 39B, 824 ClbHj 3O9OS3PS2 f (M"Hydrido)-(M"dithioformato)-bis(tricarbonyl-osmium)-tricarbonyl(dimethylphenylphosphine)osmium, 46B, 1212 ClbHi5Cl2HgPSe, Triphenylphosphine selenide mercury(II) chloride, 40B, 1128... 

A mixture of methyl tridiloracetate, propylene, benzene, and cyclopentadienyl-molybdenum tricarbonyl dimer as catalyst in a glass vessel heated 16 hrs. at 150° in an autoclave 2,2-didiloro--4-methyl-y-butyrolactone. Y 98.7%. F. e. s. Y. Mori and J. Tsuji, Tetrahedron 28, 29 (1972). 

Tricarbonyl(6,6-diphenylfulvene)chromium(0) (52) was obtained by reaction of 6,6-diphenylfulvene with hexacarbonylchromium in 64% yield [56]. Later it was shown that almost quantitative yields can be obtained under photochemical reaction conditions starting from (benzene)Cr(CO)3 or from (mesitylene)Cr(CO)3 as the complexation reagent [63]. The corresponding molybdenum and tungsten complexes were prepared by treatment of the ligands with tris(acetonitrile)M(CO)3 (M = Mo, W) [64]. Olefin complex 53 was obtained by Wilkinson and Altman in 51% yield from 6,6-diphenylfulvene and bis(dicarbonylchlororhodium). Similar complexes were prepared with other rhodium reagents [58]. Hiibel and Weiss [59] prepared the diene tri-carbonyliron complex 54 (11-30%) in addition to the dinuclear complex, in which either one of the endocyclic double bonds is coordinated at Fe(CO)4 (49-66%). 

Substituted-benzene-metal tricarbonyls of chromium, molybdenum, and tungsten do not have any intense band in the 900 to 980 cm range, while the parent compounds absorb at 902 and 978 cm, respectively 131). The IR spectra of hexamethyl-, hexaethyl-, and iefa-diisopropylbenzene(Mo, W) tricarbonyls show weak to medium intensity bands, probably due to some... 

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