Acetylene derivs complex

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

The above-postulated overall mechanism considers two alternative pathways depending on the nature of the acetylene derivative. Region A outlines a proposal in which the formation of the a-complex intermediate is supported by the fact that the treatment of aliphatic terminal acetylenes with FeCl3 led to 2-chloro-l-alkenes or methyl ketones (Scheme 12). The catalytic cycle outlined in region B invoked the formation of the oxetene. Any attempt to control the final balance of the obtained... 

The compounds 93 (R = Me, Et) are extremely sensitive toward oxidation and moisture and were not isolated in a pure state. Their structures were supported by NMR spectroscopy. Treatment of 93 with pyridine also gives rise to pyridine-l-boraadamantane complex 111 and starting acetylene derivative, via 1,1-deorganoboration. Accordingly, the 1-boraadamantane-TMEDA adduct (TMEDA - bis(dimethylamino)ethane) (along with Me3SnC CSnMc() is formed when the tricyclic borane 93a (R=Me) reacts with TMEDA <2003JOM(687)108>. 

During the last ten years, the chemistry of 1,1-boriozirconocene complexes has been studied. Both hydrozirconation and hydroboration reactions are well established, and are widely applicable to a wide variety of vinyl and acetylene derivatives [1], Alkenylboranes and alkenylzirconium compounds can also be readily prepared. Therefore, hydrometalla-tion of the corresponding alkenyl metals should offer a convenient method for preparing gem-boriozirconocenes [24]. 

This observation may well explain the considerable difference between metal-olefin and metal-acetylene chemistry observed for the trinuclear metal carbonyl compounds of this group. As with iron, ruthenium and osmium have an extensive and rich chemistry, with acetylenic complexes involving in many instances polymerization reactions, and, as noted above for both ruthenium and osmium trinuclear carbonyl derivatives, olefin addition normally occurs with interaction at one olefin center. The main metal-ligand framework is often the same for both acetylene and olefin adducts, and differs in that, for the olefin complexes, two metal-hydrogen bonds are formed by transfer of hydrogen from the olefin. The steric requirements of these two edgebridging hydrogen atoms appear to be considerable and may reduce the tendency for the addition of the second olefin molecule to the metal cluster unit and hence restrict the equivalent chemistry to that observed for the acetylene derivatives. 

The explosive carbonylalkali-metals , previously formulated as monomeric compounds, are either dimeric acetylene derivatives of the general formula MOC=COM. or are trimers of the latter and formulated as salts of hexahydroxybenzene. Many true carbonylmetal complexes are air-sensitive and pyrophoric, not always immediately. Individually indexed compounds are Bis(dicarbonylcyclopentadienyliron)-bis(tetrahydrofuran)magnesium, 3835... 

Catalytic forms of copper, mercury and silver acetylides, supported on alumina, carbon or silica and used for polymerisation of alkanes, are relatively stable [3], In contact with acetylene, silver and mercury salts will also give explosive acetylides, the mercury derivatives being complex [4], Many of the metal acetylides react violently with oxidants. Impact sensitivities of the dry copper derivatives of acetylene, buten-3-yne and l,3-hexadien-5-yne were determined as 2.4, 2.4 and 4.0 kg m, respectively. The copper derivative of a polyacetylene mixture generated by low-temperature polymerisation of acetylene detonated under 1.2 kg m impact. Sensitivities were much lower for the moist compounds [5], Explosive copper and silver derivatives give non-explosive complexes with trimethyl-, tributyl- or triphenyl-phosphine [6], Formation of silver acetylide on silver-containing solders needs higher acetylene and ammonia concentrations than for formation of copper acetylide. Acetylides are always formed on brass and copper or on silver-containing solders in an atmosphere of acetylene derived from calcium carbide (and which contains traces of phosphine). Silver acetylide is a more efficient explosion initiator than copper acetylide [7],... 

Cassar, J. Synthesis of Aryl- and Vinyl-substituted Acetylene Derivatives by the Use of Nickel and Palladium Complexes, J. Organomet. Chem. 1975,93, 253. 

An early procedure used triethyl phosphate directly on the diketone, but better yields are obtained by the oxidation of the corresponding dihydrazone 42 The oxidant may be mercury(n) oxide, which is rather expensive 43 alternatively copper(i) chloride in dichloromethane and pyridine is oxidised with oxygen gas, and the derived complex is then used to oxidise the dihydrazone to the acetylenic group with the evolution of nitrogen.44 The reaction is illustrated by the conversion of benzil dihydrazone into diphenylacetylene (Expt 5.25). 

Although the acetylene derivatives Co2(CO)6(C6H5C=CCOOH) and Co3(CO)9(H)(CH=CC6H5) were also found to initiate polymerization in the presence of CC14) Co2(CO)8 was found to be not only inactive, but actually to inhibit polymerization in the presence of conventional free radical initiators. The unusual behavior of dicobalt octacarbonyl may be related to its greater reactivity. The reaction with carbon tetrachloride has been studied by Dent et al. (22a) and Ercoli et al. (26a) who isolated a complex C1C [Co(CO)3]3. This could arise from a series of C—Cl cleavage reactions... 

Optimal synthetic methods for obtaining these complexes have been developed including, for example, the interaction of acetylene derivatives, atomic selenium, and cyclopentadienyl complexes [638,640]. In some derivatives of 1,2,3-selenodia-zole, structure 343 can be transformed to 339, as shown by reaction (2.7) [641] ... 

Ozaki and co-workers <1998TL8121> applied an electrochemical method for the synthesis of thietanes by the electroreduction of the acetylenic derivative of thioacetic acid 52. The electrochemical reaction was carried out in dimethylformamide (DMF) using tetraethylammonium perchlorate as a supporting electrolyte at a graphite plate electrode in the presence of an N,N -bis(salicylaldehydo)ethylenediamine (salen) nickel complex 54 (Equation 19). The desired 2-benzylidene-4-ethyl-thietane 53 was obtained in fair yield. 

The RCCo3(CO)9 catalysts in these reactions, however, only appear to be sources of simpler cobalt carbonyl species through their thermolysis, and it is the latter which cause the acetylene trimerization through well-established routes (73). Indeed, in some cases acetylene-derived cobalt carbonyl complexes are obtained (72) ... 

Pericyclic reactions involving thiophenes have been utilized to prepare a variety of complex heterocycles. The intramolecular Diels-Alder reaction of 2-vinylbenzo[i]thiophene 92 produced a pair of tetracyclic adducts 93 and 94 <02TL3963>. Coupling of Fischer carbene 96 with 3-alkynylthiophene 95 led to the formation of thieno[2,3-c]pyran-3-one 97 in one step <02JOC4177>. An intramolecular cycloaddition of 97 then afforded tetracyclic adduct 98. A ruthenium-catalyzed cyclodimerization reaction involving bis-thienyl acetylene derivatives was... 

Related tungsten complexes have been prepared by diverse routes. Phosphine, phosphite, and isonitrile W(CO)2(RC=CR)LI2 complexes form from W(CO)4LI2 and alkyne [Eq. (3)] (44). Parent acetylene (HC2H) complexes were isolated as m-dicarbonyl derivatives for L equal to PMe3 or AsMe3, and both cis- and Pms-dicarbonyl derivatives were characterized with phenylacetylene in the coordination sphere. 

A variety of alkynyl derivatives, including trimethylsilyl acetylene and terminal acetylene derivatives, have also been prepared by delithi-ation reactions with N3P3F6 (77, 79). The terminal silyl group of the trimethylsilyl acetylene derivatives has been substituted by H using KF and EtOH. The alkynyl groups of some of these substituted phos-phazenes have been found to react with Co2(CO)8, forming Co2(CO)6 complexes (77). 

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