Molybdenum complexes cyclopentadienyls

The retrosynthetic analysis of the 2-oxygenated carbazole alkaloids, 2-methoxy-3-methylcarbazole (37), O-methylmukonal (glycosinine) (38), 2-hydroxy-3-methylcar-bazole (52), and mukonal (53) based on the molybdenum-mediated approach led to the molybdenum-complexed cation (663) and 3-methoxy-4-methylaniline (655) as precursors (Scheme 5.51). The cationic molybdenum complex, dicarbonyl (ri -cyclohexadiene)(r -cyclopentadienyl)molybdenum hexafluorophosphate (663), required for the electrophilic substitution, was easily prepared quantitatively through known literature procedures (586,587). 

Tables I and II summarize the structural studies of mononuclear and binuclear vinylidene complexes, and Table III those of propadienylidene complexes which had been reported to mid-1982. As can be seen, the C=C bond lengths range from 1.29 to 1.38 A, and the M-C bond (1.7-2.0 A) is considerably shorter than those found in alkyl or simple carbene complexes. Both observations are consistent with the theoretical picture outlined above, and in particular, the short M-C bonds confirm the efficient transfer of electron density to the n orbitals. In mononuclear complexes, the M—C=C system ranges from strictly linear to appreciably bent, e.g., 167° in MoCl[C=C(CN)2][P(OMe3)2]2(fj-C5H5) these variations have been attributed to electronic rather than steric factors. In the molybdenum complex cited, the vinylidene ligand bends towards the cyclopentadienyl ring (111).

Phthalic acid, with trinuclear Os clusters, 6, 743 n-acceptor carbon ligands, in molybdenum carbonyls, 5, 455 Ti-allyl complexes, with molybdenum with cyclopentadienyl-supporting ligands, 5, 544 monomeric complexes, 5, 546 oxide surface binding, 5, 546... 

Sakthivel, A., Zhao, J. and Kuhn, F. E. Cyclopentadienyl molybdenum complexes grafted on zeolites - synthesis and catalytic application, Catal. Lett., 2005, 102, 115-119. 

More contrasting behavior is displayed by the somewhat related molybdenum complex of l-[(dimethylamino)methyl]-2-(diphenylphosphino)ferrocene, (FcCNP)-Mo(CO)4, in which the octahedral geometry around the molybdenum atom is achievd by coordination of one P atom and one N atom of the adjacent substituents attached to a single cyclopentadienyl ring (see the sketch in Fig. 7-10). In CH2CI2, the irreversible oxidation of the molybdenum fragment precedes the reversible oxidation of the ferrocene moiety [40],... 

All three (t7 CsH5)M(NO)2C1 complexes are prepared in a similar manner, but to achieve maximum yields of the chromium and tungsten compounds, the reactions must be performed at -78°. The molybdenum complex (chloro(Tj -cyclopentadienyl)nitrosylmolybdenum), on the other hand, can be obtained in excellent yields even at room temperature and its preparation is detailed below. 

Ethene, molybdenum complex, 26 102 rhenium complex, 26 110 Europium, tetrakis[T) -l, 3-bis(trimethyl-silyl)cyclopentadienyl]di-p.-chloro-di-, 27 171... 

The driving force of aromaticity can be exploited for C-C bond cleavage in prearomatic systems. Pentamethylcyclopentadienyl complexes are obtained from reactions of hexamethyl-(Dewar benzene) with RhCl3 and IrCl3 [56]. A r 4-(en-do-ethylcyclopentadienyl)molybdenum complex rearranges with breaking of the Cp-Et bond to a r 5-(cyclopentadienyl)(ethyl)molybdenum complex upon generation of a vacant coordination site on the metal [57]. 

Treatment of the carbyne complexes (// -cyclopentadienyl)(CO)[P(OMe)3]M = CR 1, where M = molybdenum or tungsten and R = cyclopropyl, with hydrogen chloride in diethyl ether results in a rearrangement reaction to give 7 -acyl complexes 2 in quantitative yield. 

Catalytic olefin epoxidation with T -cyclopentadienyl molybdenum complexes 12COC16. 

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... 

Treatment of Cp"Cr(Ti -Cot), Cp" = Cp, Cp with (EtCN)3M(CO)3, M = Mo, W and Fe2(CO)9 affords the complexes [(Cp Cr)(CO)3M][ i-Cot], M = Fe, Cr, W, Cp = Cp and I(Cp Cr)(CO)3Crl/i-Cot, Cot = Cyclooctatetrane, which have been spectroscopically characterised. Bimetallic complexes containing bis(tetramethylcyclopentadienyl) dimethylsilane bridges have been prepared from the reaction of arene tricarbonyl molybdenum complexes with the silyl substituted cyclopentadienyl derivative. The synthesis of pinanylcyclopentadienes followed by metallation and reaction with Mo(CO)s and Mel gives the chiral (-)-[(ii -C5Me4-3-pinanyl)(CO)3Me], which has been structurally characterised. The chiral methallyl complexes CpMo(NO)X(Ti -2-methallyl) X = camphorsulfonate have been resolved and the reactions of the... 

McCleverty, J.A., Seddon, D., Bailey, N.A., and Walker, N.W. (1976) The chemistry of cyclopentadienyl and related nitrosyl complexes of molybdenum, part 5. Dihalogenonitrosyl tris(pyazolyl)borato]molybdenum complexes, dieir alcoholysis, and the crystal and molecular structure of chloronitrosylisopropoxo[tris(4-chlotD-3,5-dimethylpyrazoyl)borato]molybdenum, J.Chem.Sco., Dalton Trans, 898-908. 

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