Complexes Derived from Acetylenes

Reaction of hexa-2,4-diyne with Fe(CO)6 yields the cyclopentadienone complex (108), characterized crystallographically. Reaction of Fe(CNBu )6 with PhC=CPh yields (109), characterized crystallographically. The ion HFe(CO)4 reacts with acetylenes HC=CCOR to yield products of structure (110), although a crystal structure determination indicates some contribution from a -olefin- -acyl structure. Protonation of (110) yields Fe[t -HRC=C(H)(COR)](CO)4 via an intramolecular decarbonylation. - Photochemical reaction between 

The complex Cp2Ti(CO)(PhC=CPh) has been prepared a structural determination indicates that the complex is best regarded as metallocyclopropene.  

Me) with CO has been shown to have a Pt2(CO)2(PPh3)a(/i-acetylene) structure, with the bridging acetylene collinear with the M-M bond. Reaction of the same acetylene with [Pt2H2(/i-H)(/ -dppm)2](PFg) in CH2CI2 results in elimination of hydrogen to give (117).  

Photochemical reaction of CpFe(CO)aR complexes (R = Me, CHaPh) with CFsC=CH yields, in addition to the insertion product CpFe[C(CF3)]=C(H)R]-(CO)2, the -pyranyl and -cyclohexadienyl complexes (118) and (119). Addition of MeOaCC CCOaMe to the t -allyl (120) results in formal insertion to give (121), but the cyclopentane (123) is obtained on reaction of (122) with the same acetylene. Reaction of (CO)4Fe(SiPh2)aFe(CO)4 with RC=CR yields complexes of structure (124), while (125) may also be isolated where R=Me. Full details on the reactivity of Fe(CNBu )5, including that with PhC=CPh to give (126), have appeared. -  

Reaction of CpMCl(CF3C=CCF8)a (M = Mo, W) with Coa(CO)8 yields bridged complexes of structure (127), which on heating undergo cyclization to 

Puddephatt and M. A. Thompson, Inorg. Chim. Acta, 1980, 45, L281. 

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Only seven of the nine carbonyl groups can be liberated as carbon monoxide, indicating that two carbonyl groups have combined with the acetylene to form a new ligand. X-ray studies on the complex derived from acetylene show that the complex contains an unsaturated lactone ring as shown in (LXIII) (160). An important structural feature of (LXIII) is that the... 

Similarly, acetylene or any acetylene of the formula RC CH is polymerized by the acetylene-cobalt carbonyl complex III at room temperature complexes derived from acetylenes with no hydrogen atom (RC=CR) do not catalyze these polymerizations (16). 

V. Iron Carbonyl Complexes Derived from Acetylenes. ... 

IRON CARBONYL COMPLEXES DERIVED FROM ACETYLENES... 

It is also possible to carry out a substrate-controlled reaction with aldehydes in an asymmetric way by starting with an acetylene bearing an optically active ester group, as shown in Eq. 9.8 [22]. The titanium—acetylene complexes derived from silyl propiolates having a camphor-derived auxiliary react with aldehydes with excellent diastereoselectivity. The reaction thus offers a convenient entry to optically active Baylis—Hillman-type allyl alcohols bearing a substituent (3 to the acrylate group, which have hitherto proved difficult to prepare by the Baylis—Hillman reaction itself. 

S)-(-)-CITRONELLOL from geraniol. An asymmetrically catalyzed Diels-Alder reaction is used to prepare (1 R)-1,3,4-TRIMETHYL-3-C YCLOHEXENE-1 -CARBOXALDEHYDE with an (acyloxy)borane complex derived from L-(+)-tartaric acid as the catalyst. A high-yield procedure for the rearrangement of epoxides to carbonyl compounds catalyzed by METHYLALUMINUM BIS(4-BROMO-2,6-DI-tert-BUTYLPHENOXIDE) is demonstrated with a preparation of DIPHENYL-ACETALDEHYDE from stilbene oxide. A palladium/copper catalyst system is used to prepare (Z)-2-BROMO-5-(TRIMETHYLSILYL)-2-PENTEN-4-YNOIC ACID ETHYL ESTER. The coupling of vinyl and aryl halides with acetylenes is a powerful carbon-carbon bond-forming reaction, particularly valuable for the construction of such enyne systems. 

This review deals with metal-hydrocarbon complexes under the following headings (1) the nature of the metal-olefin and -acetylene bond (2) olefin complexes (3) acetylene complexes (4) rr-allylic complexes and (5) complexes in which the ligand is not the original olefin or acetylene, but a molecule produced from it during complex formation. ir-Cyclopentadienyl complexes, formed by reaction of cyclopentadiene or its derivatives with metal salts or carbonyls (78, 217), are not discussed in this review, neither are complexes derived from aromatic systems, e.g., benzene, the cyclo-pentadienyl anion, and the cycloheptatrienyl cation (74, 78, 217), and from acetylides (169, 170), which have been reviewed elsewhere. 

X-ray studies (193) on the complex derived from diphenylacetylene show that it has the structure (XXXV M = Co), in which th.e C—C bond of the acetylene is normal to the Co—Co bond. Although at a preliminary stage of refinement, the results also show that the configuration of the acetylene has changed considerably on complex formation, e.g., the C C bond has increased in length to 1.46A, and the Ph—O—C angle is no longer 180°, but 137°. 

They noted that in dimethoxyethane or in iso-octane (path a), the major product was dicarbonylcyclopentadienylcobalt (2) which must arise as a result of a retro Diels-Alder reaction of the norbornadiene (which would lead to the formation of acetylene and cyclopentadiene). When the solvent was changed to an aromatic hydrocarbon such as benzene or toluene (path b), the major cobalt-containing product was shown to be a complex derived from Co4(CO)i2, with three CO ligands on an apical cobalt being replaced by a molecule of the aromatic solvent (3). The group noted that they were also obtaining hydrocarbon and ketonic products derived from norbornadiene, acetylene and carbon monoxide .1,2... 

Even a rod-like backbone derived from acetylene is conceivable and has been realised by Liu et al. [367] starting from l,4-dichlorobutin-2. The usual reaction with methyl imidazole and subsequent reaction with silver(l) oxide and carbene transfer to gold(I) [Au(SEtj)Cl] makes the dimeric silver(I) and gold(l) complexes accessible featuring argentophilic and aurophilic interactions, respectively. 

Titanium-alkyne complexes Ti(Me3SiC=CC6Hi3)(OR)2, as well as the chiral complex derived from chloro-tris[(—)-menthoxo]titanium/2MgClPr1 and alkynes, react with carbonyl compounds to afford optically active allylic alcohols in up to 38% ee (Scheme 127).184 Introduction of two different electrophiles at each of the acetylenic terminal carbon atoms was possible in a regio- and stereoselective manner.45 Similarly, the titanacyclopentene compounds react with imines, metalloimines, or hydrazones under mild conditions to afford allylic amines or their derivatives in good to excellent yields (Scheme 128).258... 

The anti-proliferative effects of some dicobalt hexacarbonyl alkyne complexes derived from aspirin 21, from diphenyl acetylene 22, and from 2-propyn-l-ol have been studied on various cell lines, including... 

TMS acetylene has been added to aromatic aldehydes in high ee, using an amino alcohol/zinc complex derived from prolinol. ... 

A series of alkyne cobalt hexacarbonyl complexes was synthesized by Jung et al. [116] and Gust et al. [117-119], These include, for example, Co2(CO)g complexes derived from aspirin 40, from diphenyl acetylene 41 and from 2-propyn-l-ol 42. 

COMC(6)455R P M. Maitlis, P Espinet, and M. J. H. Russell, Comp. Organomet. Chem., 1982, 6, 455 69. Palladium Complexes Derived from Reactions with Acetylenes. II... 

Figure 50. Proposed mechanism of formation of arene-chromium derivatives from acetylenes and chromium-aryl complexes.

A mechanism based on the intermediate formation of an 7 -benzene complex derived from coupling of the alkyne with the iridacyclopentadiene moiety has been proposed on the basis of the isolation of [(ttiphos)Ir( -C6H6)]PF5 441 from the reaction of [(triphos)IrCI(CFI=CFI-CH=CH)] 442 with acetylene in the presence of TIPF6. In O Connor s system, it is conceivable that the pending ester function in the putative -arene intermediate may drive the reaction toward the C-H activation and the formation of aryl(hydride) species 440 and 441. ... 

The complexes derived from several acetylenes have been oxidized with ferric chloride to produce, upon loss of an iron carbonyl residue, the corresponding derivatives of (CVI) 121). 

A more complex carbonylation process is involved in the formation of bisbutenolides (bifurandiones) from cobalt carbonyl-catalyzed carbonylation of alkynes112 117 (Scheme 68). The trans derivative (53) is formed in good yield from acetylene,112 but yields from substituted acetylenes (e.g., propyne)... 

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