Diynyl complex

The reaction of ZrCl 2-N(SiMe3)-4-MeC5H4N 3 with LiC=CC=CSiMe3 gives a structurally characterized mono-diynyl complex 1. ... 

However, reactions with the more electron-rich substrate MoBr(CO)(dppe)Cp and HCsCC=CH were rather less successful, and the terminal diynyl complex was isolated in only moderate yield. Deprotonation of the latter was achieved with LiBu or LiNPr 2, the resulting lithio derivative being trapped with SiClMe3. 

Several diynyl complexes of Group 6 metals have been prepared directly from LiC=CCsCSiMe3. In the cases of WCl(CO)3Cp, >4 MoCl(CO)(dppe)Cp,i and MoBr(CO)2(/ -C7H7) the silyl-diynyl complexes could be isolated in low to moderate yields. In all cases, proto-desilylation was achieved using KF in MeOH/thf. The terminal diynyl complexes were also obtained from MoBr(CO)(L) r -C H ) (L = CO, PMes) and Li2C4 in low yield. 

In addition to their role as a source of lithiated diynes or terminal diynes silyl-protected diynes have found direct application in the preparation of Group 8 diynyl complexes. Reactions of Me3SiC=CC=CR (R = Ph, C=CPh, C=CC=CPh) with RuCl(PPh3)2Cp in the presence of KF afford the corresponding poly-ynyl complexes Ru(C=CC=CR)(PPh3)2Cp." ... 

The diynyl ligand behaves chemically as a rather electron-rich organic alkyne. The complexes MLn C=CCsCSiMea (and those with longer chains) are readily protodesilylated under standard conditions, such as treatment with fluoride in pro-tic solvents or carbonate in methanol, to give the corresponding terminal diynyl complexes in high... 

Addition of electrophiles to diynyl complexes is expected to occur at either or C, the latter being favored if sterically demanding ligands shielding C and are present. The products are butatrienylidenes and the chemistry of these species is closely related to the chemistry of the related unsaturated carbene ligands (Section VIILB). " ... 

Several diynyl complexes react with other metal substrates, the proximity of the a-bonded metal to a multimetal system often resulting in further cluster condensation. 

The reaction of two equivalents of W(C=CC=CH)(CO)3Cp with Ru3(CO)io (NCMe)2 gives the RU3W cluster 149 (Scheme 30), which is also obtained from 135 and W(C=CC=CH)(CO)3Cp. The extended organic ligand is formed by coupling of two molecules of the diynyl complex with two of CO, to form a cyclopen-tadienone attached by a carbenic interaction to the cluster W atom, and featuring formylethynyl and C=CW(CO)3Cp substituents. " One of the elementary steps in the reaction mechanism may involve formal rearrangement of the diyne to a dicarbyne. 

The reactions of titanocene derivatives TiX(C CsCR)Cp 2 (X = C1, C= CC=CR R = SiMe3, Et) or of cis-Pt(C=CC=CR)2(PR 3)2 with mononuclear metal complexes have given numerous products in which the diynyl ligand(s) are chelated to a low-valent metal via the internal C=C fragment(s). These cis-bis(diynyl) complexes are often referred to as molecular tweezers. 

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