Tungsten complexes with isocyanides

A number of attempts have been made over the years to develop reproducible synthetic routes to six- and seven-coordinate isocyanide complexes of molybdenum and tungsten. Two of the older methods, namely, the reaction of the hexacarbonyls with halogens in the presence of an isocyanide (775,116) or reactions of the salt Ag4Mo(CN)8 with isocyanides (74), have given six- and seven-coordinate products. Recently, however, the discovery of the reductive or nonreductive cleavage of multiple metal - metal bonds in dinuclear group VIA compounds by isocyanides has provided a facile route to the synthesis of a variety of homoleptic and related isocyanide complexes of these metals in reasonable yields. 

Allyl complexes (pseudo-rotations, dynamic NMR studies, 1, 416 with tungsten carbonyls and isocyanides, 5, 688-689 rc-Allyl complexes with Cr, 5, 305 with Cr(II), 5, 300 with Cr(III), 5, 300 and cyclodextrins, 12, 789 in enyne carbometallation, 10, 328 with rhodium, 7, 220-221 (j-Allyl complexes, with iron, 6, 98 5-Allyldiisopinocampheylboranes, in asymmetric allylboration, 9, 198... 

Bis(adamantylimido) compounds, with monomeric chromium(VI) complexes, 5, 348 Bis(alkene) complexes conjugated, Rh complexes, 7, 214 mononuclear Ru and Os compounds, 6, 401 -02 in Ru and Os half-sandwich rj6-arenes, 6, 538 with tungsten carbonyls and isocyanides, 5, 685 Bis(u-alkenylcyclopentadienyl) complexes, with Ti(II), 4, 254 Bis(alkoxide) nitrogen-donor complexes, with Zr(IV), 4, 805 Bis(alkoxide) titanium alkynes, in cross-coupling, 4, 276 Bis(alkoxo) complexes, with bis-Cp Ti(IV), 4, 588 Bis[alkoxy(alkylamino)carbene]gold complexes, preparation, 2, 288... 

Bis[iV,iV -di(2-pyridyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis[iV,iV -di(2-pyridyl-methyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis(diselenolate) complexes, dinuclear iron compounds, 6, 242 Bis(dithiolene) compounds, in tungsten carbonyl and isocyanide complexes, 5, 644 Bis(enolato) complexes, with bis-Cp Ti(IV), 4, 589 Bis(enones), in reductive cyclizations, 10, 502 Bis(ethanethiolato) complexes, with bis-Cp Ti(IV), 4, 601 Bis(ethene)iridium complexes, preparation, 7, 328-329 -Bis(fluorenyl)zirconocene dichlorides, preparation,... 

Butadienyl complexes, with platinum, 8, 656 7]3-l,3-Butadienyl complexes, with tungsten carbonyls and isocyanides, 5, 689... 

Fulvalenes, with bis-Cp Ti(IV), 4, 587 Fulvalene thiolates, in tungsten carbonyl and isocyanide complexes, 5, 644... 

A series of stable chromium and tungsten Fischer dienyl carbenes 66 were prepared by 1,3-DC of alkenylethynyl carbene complexes 65 with nitrones. Treatment of isoxazolines with isocyanides afforded highly functionalised 2,3-dihydro-l,2-benzisoxazoles 67 in a completely selective fashion and with high yields <01CEJ5318>. 

Molybdenum(IV) and tungsten(IV) compounds may be obtained by alkylation utilizing RX, while reactions of [M(CN)g] with isocyanides RNC lead to complexes in lower oxidation state. 

It has been reportedthat a C-C bond in an aromatic ring is cleaved with a stoichiometric amount of a transition metal complex. When quinoxaline was treated with the tungsten complex 90, dihydrogen was released and the tungsten was inserted into the C-C bond to furnish the di(isocyanide) tungsten complex 92 (Scheme 7.37) [52]. The authors proposed the mechanism to be through sequential C-H... 

In a final variation, the hexafluorobutyne-molybdenum and -tungsten complexes (XX) and (XXI) react with excess tert-butyl isocyanide to afford iminocyclopentadiene complexes (Davidson et al, 1975). Release of the diene ligand from this complex was not reported. 

In a three-component reaction, a cationic platinum isocyanide complex [(Ph3P)2Pt(CNR)Cl][BF4] is reacted with a /3-bromoamine and butyl lithium to give an imidazoldin-2-ylidene complex.This transformation can be a two-component reaction if the isocyanide ligand contains already the necessary amine functionality. This was shown for chromium, molybdenum, tungsten, and rhenium carbonyls. 

The striking advance since 1973 has been the synthesis of homoleptic isocyanides for vanadium and almost all of the post-group-VIA metals up to group IB (see Table I), and this has been helped in some respects by synthetic rationale. For example, the discovery of the simple reductive or nonreduc-tive cleavage of multiple metal-metal bonds in suitable dinuclear complexes of molybdenum and tungsten has provided a high yield route to W(CNPh)6 and [M(CNR)7]2+ (M = Mo, W) and related complexes (5-14). During these studies the series [M(CNR)7]2+ was completed with the isola-... 

Perfluoro-triamido-amines, with tungsten, 5, 744 Perhalophenylgold(I) isocyanides, liquid crystals, 12, 282-283 Perhydrocarbyl complexes... 

---