Alkyls homoleptic, tungsten

Hexaalkoxides are only known for the two elements tungsten and uranium. In both cases, physical and spectroscopic data are consistent with monomeric, octahedral complexes. Tungsten hexaalkoxides are pale yellow or colorless substances that readily sublime and exhibit the expected H NMR and mass spectra.189 The totally symmetric v(W—O) stretch occurs between 530 and 600 cm-1 in the IR spectrum, depending on the alkyl substituents. In contrast, the homoleptic phenoxide W(OPh)6 is intense red in color due to the presence of a strong oxygen-to-metal charge transfer band in this d° complex which absorbs in the visible part of the spectrum.36... 

Neutral and cationic homoleptic see Homoleptic Compound) tungsten-isocyanide complexes W(CNR)6 and [W(CNR)7] + (R = alkyl, aryl) are known, and W(CO)6-n(CNR) (n=l-3) complexes may be prepared from W(CO)6 and excess isocyanide in the presence of catalytic amounts of C0CI2 or PdO. Isocyanides are isoelectronic with CO and also insert into the W-R bonds of alkyl complexes see Alkyl Complexei). For instance, the alkyl-nitrosyl complexes Cp"W(NO)(X)(CH2BuO (X = NHBuC OBu ) react with CNBu to afford -iminoacyl complexes, and the isocyanide complexes, Cp W(CO)2(Me)(CNR) (10, R = alkyl), rearrange to afford either jj -iminoacyl Cp W(CO)2( -MeCNR) (11) or Li azaallyl Cp"W(CO)2(/ 3-CH2CHNR) (12) derivatives, depending upon the reaction conditions (equation 4). ... 

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