Vinylidene complexes Procedure

Beside the aromatic vinylidene complexes also alkyl vinylidene complexes [Ru(bdmpza)Cl(=C=CHPr)(PPh3)] (33c) and [Ru(bdmpza) Cl(=C=CHBu)(PPh3)] (33d) have been synthesized (Scheme 20), following the same procedure as earlier by using 1-pentyne or 1-hexyne. IR and NMR spectroscopic data of 33c and 33d are similar to those of 33a and 33b. Again only one major isomer was isolated in the case of [Ru(bdmpza)Cl(=C=CHPr)(PPh3)] (33c), though the... 

Experimental Procedure 3.1.2. Preparation of an Iron Vinylidene Complex by Electrophilic Abstraction CarbonyUrj -cyclopentadienyOldimethylvinylidene)-(triphenylphosphine)iron tetrafluoroborate [464J... 

Experimental Procedure 3.1.4. Preparation of a Molybdenum Vinylidene Complex from a Carbyne Complex Tetrabutylanunoniuih Cyano(ethoxycarbonyl) vinylidene (dicarbonyl) hydro-tris(3,5-dimethyl-1 -pyrazblyl)borato molybdenum [526] [37] pp 151 and 188... 

The incorporation of the second equivalent of imine can be prevented in these reactions if a vinylidene complex, such as (31), is employed which is 3optimized conditions indicated, the reaction of (31) with A -meAyl benzaldehyde imine will provide the cycloadduct (32) in quite good yield. A rather unc odox oxidation procedure (BU4NNO2, 6.5 kbar 1 bar = 10 Pa) is required for the effective cleavage of the cationic complex (32) to the 3-lactam (33). This reaction was shown to involve a two-step process, since the salt (37) could be isolated in 80% yield by column chromatography if the reaction was stO[q)ed shortly after the reaction mixture was Ivought to room tenq>erature. The reaction with the cyclic thioimidate (34) indicates that vinylidene complexes can be useful in the synthesis of functionalized 3-lactams in good yields with high stereoselectivity. 

Ethyne and terminal alkynes show a different behavior. When ethene complex 339 was treated with ethyne at 20 °C, vinylidene complex 347 was obtained in 20% yield. This yield was improved to 88% by using the alternative procedure starting from 338, thus making 347 available in multigram quanti-ties69.7o (Scheme 63). The characteristic spectroscopic... 

Switching the cubic nonlinearity of ruthenium alkynyl complexes by a protmi-ation/deprotonation sequence (via a vinylidene complex) was demraistrated by fs Z-scan studies at 800 nm several years ago [41]. Recently, protic and electrochemical switching were demonstrated in the ruthenium alkynyl cruciform complex 11 for which distinct linear optical and NLO behavior were noted for the vinylidene complex and the Ru(II) and Ru(III) alkynyl complexes [42]. Because the oxidation/ reduction and protonation/deprotonation procedures are independent, this system corresponds to switching by orthogonal stimuli. 

Scheme 5.9 Improved procedure for the formation of a cyclic Fischer-carbene complex via vinylidene by Ddtz.

Vinylidene (3), as well as related vinylidenes, have been obtained in good yields via the addition of electrophiles to acetylide complexes. The procedure below allows one to make these vinylidenes without the use of alkali metal acetylide reagents. Solid vinylidene 3 is not sensitive to air or water making it an attractive starting material. 

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