Molybdenum, chloro derivatives

When methylene chloride was used as a solvent, it was found that 28 are obtained in minor amounts, while the dominating product is the -coordinated chloro-carbyne species [(> -Tp )Mo(CO)2(=CCl)], whose yield increases abruptly with substitution in the pyrazol-l-yl fragments (3-methyl-, 3,4,5-trimethyl-, and 3,5-dimethyl-4-chloro derivatives) [90AX(C)59,95JCS(D) 1709]. The tungsten analog can be prepared similarly. The chlorocarbyne molybdenum complex follows also from the reaction of the parent anion with triphenylsulfonium cation but conducted in dichloromethane. The bromo- and iodocarbyne derivatives are made similarly. 

Divalent molybdenum compounds occur in mononuclear, dinuclear, and hexanuclear forms. Selected examples are shown in Figure 6. The mononuclear compounds are mostiy in the realm of organometaUic chemistry (30—32). Seven-coordinate complexes are common and include MoX2(CO)2(PR3)2, where X = Cl, Br, and I, and R = alkyl MoCl2(P(CH3)3)4, heptakis(isonitrile) complexes of the form Mo(CNR) 2 (Fig. 6d), and their chloro-substituted derivatives, eg, Mo(CNR)3CR. The latter undergo reductive coupling to form C—C bonds in the molybdenum coordination sphere (33). 

In the course of a study of the formation of fluorophosphoranes from chloro-phosphines (22) we observed one exception in the compound chloromethyldi-chlorophosphine, which reacted smoothly with antimony trifluoride to give the flammable fluorophosphine, C1CH2PF2, under conditions where many other chloro-phosphines were invariably converted into fluorophosphoranes. As this fluorophosphine is readily available, its interaction with a metal carbonyl derivative was studied, and cycloheptatriene molybdenum tricarbonyl, obtained from the reaction of molybdenum hexacarbonyl with cycloheptatriene (I, 2), was chosen as a starting compound. 

The enolates (48) and (49) of the transition metals tungsten, rhenium and molybdenum can be successfully prepared by the nucleophilic displacement of a-chloro ketones and a-chloro esters with the appropriate transition metal anion (Scheme 6). They are isolated as C-bound enolate derivatives and, except for the rhenium enolate (49), do not undergo thermal aldol additions to benzaldehyde. However, Bergman and Heathcock et al. have found that an aldol reaction of complex (48) with benzaldehyde can occur on irradiation via the rearranged q -oxaallyl derivative (50), where the metal aldolate (51) can then be... 

Spectroscopic and chemical studies of vanadyl OEP have been reported, including m 50-substitution to form nitro-, chloro-, and benzoyloxy-derivatives trans-alkylation occurs when the vanadyl porphyrin is heated on clay and other supports, thus providing a model for the generation of homologous polyalkyl-porphyrins in crude oil and bitumen. m sa-Tetraferrocenyl-porphyrin and its copper complex have been prepared, and spectroscopic and other studies carried out on mixed-valence oxidation products, as models for the study of thermal electron-transfer processes in cytochrome-c. X-Ray crystal structures have been reported for diaquo and perchlorate complexes of Fe" TPP, " dichloro-molybdenum complexes of OEP and TPP, and for the bis-[(R5)-l-phenyl-ethylamine] complex " of Co TPP. Oxomolybdenum complexes TPP-... 

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