Tungsten hexacarbonyl, complexes with

Chromium or tungsten hexacarbonyl react with the dilithiated dianimis, LiNRCH2C(R )CHLi, to give lithiated butyrolactams. Initial attack of the dianion on a coordinated carbonyl results in an anionic carbene complex which undergoes an intramolecular cyclisation to the product. ... 

Molybdenum and tungsten hexacarbonyls are able to form anionic complexes (AsPli4)2[(OC)4M( -pz)2M(CO)4] upon reaction with sodium pyrazolate and PluAsCl (72CB3203). The cationic complexes [(rj -Cp)2Mo(/Lt-pz)2Mo(rj -Cp)2] " (n = 2, 3) are known as well (74HCA1988). The other representatives of the complexes containing an exobidentate ligand (26) are derived from 4//-pyrazoles [70ZAAC(379)169]. 

Nucleophilic acyl complexes can be 0-alkylated with hard electrophiles to yield the corresponding alkoxy- or (acyloxy)carbene complexes. The first carbene complex ever isolated [61] was prepared by this route the intermediate, anionic acyl complex was generated by addition of phenyllithium to tungsten hexacarbonyl (Figure 2.3). 

The heat of formation of [MolCOlg] has been determined as -960 + 12 kJ mol by measuring its heat of decomposition. The Mossbauer parameters for the 100 keV transition of in [W(CO)g] and some tungsten(vi) complexes have been measured and discussed in terms of known bonding and structure. Secondary ions [M (CO) ] (M = Mo, m = I or 2 M = W, m = 1—4 n = 0—14) formed by ion-molecule reactions have been observed in the mass spectra of the hexacarbonyls. A mixt u re of [Cr(CO) ] and [MolCO) ] vapours affords [CrMo(CO) ] ( = 5—7). [MofCOl ] and [WICO) ] catalyse the condensation of isocyanates with aldehydes to give imines in high yields. ... 

Diene complexes of the type [W(CO)4(diene)l (VI M = W) are formed by cyclo-octa-1,5-diene (79, 151), hexa-1,5-diene (151), and dimethyldi-vinylsilane (158) on heating with tungsten hexacarbonyl. Cycloheptatriene (158) displaces cyclo-octa-1,5-diene and 1 mol. of carbon monoxide from its tungsten complex ... 

Treatment of tungsten hexacarbonyl with a mixture of cyclo-octa-1,3,5-and -1,3,6-triene gives the complex [W(OO iCslIiohJ (85). The hydrocarbon is believed to be the 1,3,6-triene, acting as a diene, but for the reasons mentioned (see Section III,H) it is possible that the ligand is bicyclo[4,2,0]-octa-2,4-diene (XV). 

Tungsten hexacarbonyl on treatment with bicyclo-[4,3,0Jnona-2,4,8-triene(C9Hio) gives a brick red complex [W(CO)3(C9Hi0)J which appears to be completely analogous to the molybdenum complex [Mo(CO).i(CaH,t))] of structure (VIII) (142). 

Tungsten hexacarbonyl is reported to form a number of stable complexes with acetylenes (116, 118), but no details have been published. 

Upon UV irradiation in hydrocarbon solution, the hexacarbonyls of chromium, molybdenum, and tungsten react differently with conjugated dienes like 1,3-butadiene (la), ( )-l,3-pentadiene (lb), 2-methyl-1,3-butadiene (lc), ( , )-2,4-hexadiene (Id), ( )-2-methyl-l,3-pentadiene (le), 2-ethyl-1,3-butadiene (If), or 1,3-cyclohexadiene (Ig). Chromium hexacarbonyl (2) yields, with the acyclic dienes la-lf, tetracarbonyl-r/2-dienechromium(0) complexes (3a-3f) in a smooth reaction (8-10). With 1,3-cyclohexadiene, in addition to 3g, dicarbonylbis(>/4-l,3-cyclohexadiene)chromium(0) (4g) is obtained [Eqs. (7) and (8)j. During chromatography on silica gel, the 1,3-cyclohexadiene complex 3g dismutates readily to [Cr(CO)6] and 4g [Eq. (9)]. Under the same conditions with 2 1,3-cyclopentadiene (lh) yields, in a hydrogen-transfer reaction, the stable dicarbonyl- / 5-cyclopentadienyl-r/ 3-cyclopent-enylchromium (5) (11-13) [Eq. (10)]. 

These complexes decompose slowly in solution at 20°. When the complex (R = diethylamino) in diethyl ether is treated with carbon monoxide at 100 bar and 60° for 18 hours, tellurium, tungsten hexacarbonyl, and 3-diethylamino-l,l-diphenylpropene (77% yield) were formed3. 

Complexes of N6P6(NMe2)12 with other metal chlorides and nitrates have essentially similar structures as indicated by infrared and electronic spectroscopic data (98). Compounds N4P4Me8 and N5P5Me10(L ) react with molybdenum and tungsten hexacarbonyls... 

Most of the work is done with carbonyl complexes of group-VIA metals. Tungsten hexacarbonyl reacts at RT with methyllithium in solvents such as diethylether or THF almost quantitatively with addition of the carbanion to the carbon atom of a coordinated CO to give the lithium salt of acetylpentacarbonyl tungstate. This complex can be converted by aqueous tetramethylammonium bromide into the more stable tetramethyl-ammonium salt ... 

The crystal structure of 2-lithiated l-methyl-l,3-benzazaphosphole 35 showed it to have a dimeric structure with two THF molecules associated with each lithium. The two lithium atoms and the two C-2 atoms form a four-membered ring <20020M912>. In contrast, the N-lithiated derivative of 2,5-dimethyl-l//-l,3-benzazaphosphole exists as a monomeric species 36 in the solid state <2002JOM(646)113>. The carbene-type complex 37 derived from the lithiated species 35 on reaction with tungsten hexacarbonyl was also studied by X-ray crystallography. 

Chiral binuclear carbene complexes of the Fischer type were synthesized utilizing (/ ,/ )-l-(l-dimethylaminoethyl)-2-lithioferrocene (296). The lithiated precursor reacts with tungsten hexacarbonyl to give a bimetallic acylate, CpFe 7j -2-C5H3 C(Me)HNMe2 C(OLi)W(CO)5 (109t),... 

A pressure tube was filled under argon in one portion with the carbene complex and THF to produce a 0.02 0.03 M solution. To this solution were added 2,6-di-/er/-butyl-4-methylphenol (DBHT, 0.2 equiv) and the corresponding alkene (1.1 equiv). The tube was sealed and heated at 100 C for 3-5 h. After this time, the initial carbene complex was completely consumed, as evidenced by TLC analysis. After cooling to rt, THF was removed by distillation, the residue was taken up in EtOAc, air was bubbled into the solution for a few minutes, and then the suspension was filtered through Celite. The filtrate was concentrated under reduced pressure to yield a crude product, which was further purified by flash chromatography on silica gel to separate molybdenum or tungsten hexacarbonyl and DBHT. The pyrrol-l-ylcyclopropanes were further purified by radial layer or flash chromatography. 

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