Mercurous acetylide

Introduction of acetylene into a saturated solution of mercuric acetate in glacial acetic acid yields a substance which has an explosive character, but this is quickly lost during storage (during a week). Ferber with Romero report this substance to be mercuric acetylide and proposed the formula 2HgC2-H2C2-H20 [64]. 

An interesting compound, mercury acetylide-silver nitrate complex HgC2 3AgN03, forms by introducing acetylene to a concentrated solution of silver nitrate (about 30%) acidified by nitric acid and followed by addition of mercuric nitrate. The product precipitates from the solution [42]. 

Mercuric acetylide has never been employed in any practical explosive applicatimi. It has, however, found some use in analytical work because formatitai of the precipitate of mercuric acetylide (from an alkaline solution of mercuric iodide and potassium iodide) can be used for the quantitative determination of acetylene [1]. 

Mercurous acetylide is a gray-colored substance. It crystallizes as a monohydrate insoluble in water [2, 60, 65]. Behavior during heating is described variously, some authors stating that the substance first separates out the water of crystallization and subsequently degrades [60], while others, like Burkard and Travers, describe the substance as unable to release crystal water because heating to temperatures over 100 °C leads to decomposition [65]. Mercurous acetylide is decomposed to acetylene on treatment with hydrochloric acid [65, 66]. Reaction with iodine yields mercurous iodide and tetraiodoethylene (C2I4) with a small proportion of diiodoacetylene ( 212). 

The preparation of mercurous acetylide is not very well described in the literature. The most complete seems to be the initial work of Plimpton [66] who suspended freshly prepared mercurous acetate in water (it is insoluble) and passed acetylene through such suspension. He himself, however, reported that the gray explosive substance which forms from the acetate was not analyzed. In its properties the prepared substance resembled acetylides of copper and silver. 

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Recently some mercuric acetylides were treated with nitrosyl chloride in an inert solvent to give solutions of highly reactive nitrosoacetylenes (Eq. 26) [67], The solution of this compound was moderately stable at —78°C, but it decom-... 

Mercuric Acetylide [Quecksilber(II)-acetyl-enid, in Ger], HgCa, mw 224.63.Keiser(Ref 2) claimed to prep it by passing CaHa through Nessler s soln (an alk mercuric potassium iodide soln). The resulting white, very expl ppt proved later to be the hydrate 3HgCj +HaO. This hydrate dec at 110° and expl at higher temps. It Is in sol in w, ale eth... 

The precipitation of mercuric acetylide resulted in alkali consumption so that titrating the excess hydroxide gave a direct measure of the amount of acetylide and hence the concentration of acetylene in the gas mixture. The more usual method, precipitating silver acetylide from ammoniacal silver nitrate, was unsatisfactory in this case since the carbon monoxide in the product gases reduced the silver nitrate to silver. 

Mercuric Acetylide + Three Silver Nitrates (Complex), HgCj + 3AgNO. Wh crysts, decomp on heating without expln. Can be prepd by treating Ag2Cj + 6AgNOs with sufficient Hg(NOs)2 in HNOs soln to ppt the HgQ + 3AgNOs... 

Mercurous Acetylide [Quecksilber(I)-acetyl-enid, in Get], Hg,C,. H,0. Grey ppt, mp-lost some water on heating and then decompd or detond. Can be prepd by treating with acetylene a cold aq suspn of mercurous acetate or by treating Cu acetylide with an aq soln of mercurous nitrate. Both operations should be carried out in the absence of light... 

Mercuric halides are Lewis acids and may also be considered pseudohalogens. It is not surprising that mercuric halides readily add to many d complexes (see Table V). Thus the iridium(I) complex (XI) adds mercuric halides, but the isostructural less-reactive rhodium(I) complex does not form a stable adduct (96). Mercuric acetylides also add to the iridium complex (XI) (31). 

N-Condensed 1,5,3-dithiazepine ring from mercuric acetylides and isothiocyanates... 

Mercuric acetylide is insoluble in water, ethanol, and ether. Freshly produced mercuric acetylide dissolves well in ammonium acetate. It decomposes in solutions of potassium cyanide and sodium sulfide [14, 60, 61]. In inorganic acid solutions, mercuric acetylide slowly hydrolyzes to acetylene and the corresponding salt (rate depends on the type and concentration of the acid) [14]. Hydrochloric acid only has a slight effect on mercuric acetylide at normal temperatures and at higher temperatures it decomposes this acetylide to mercuric chloride and acetylene. 

During slow heating, mercuric acetylide slowly decomposes at 110 °C and above to mercury, carbon, and water [60, 61]. 

Storing mercuric acetylide in an ethanolic solution of mercuric chloride or even shortly boiling it in an aqueous solution of mercuric chloride leads to its transformation into a nonexplosive compound that has the same properties as the product of bubbling acetylene through a solution of mercuric chloride [60, 61]. 

Mercuric acetylide explosively decomposes to mercury and carbon in an amorphous form (like soot) [62]. Nothing else was found about explosive properties of this compound in an open literature. 

Based on the comparison with cupric acetylide it could be assumed that mercuric acetylide will form from the reaction of acetylene with a solution of mercuric chloride. This reaction gives a white precipitate, which is not HgCa, but some organomercury compound. To the substance prepared in a neutral environment, Keiser attributes the formula C2(HgCl)2 [15,63], Blitz, and Mumm (ClHglaC-CHO, Biginelli CHCl=CHHgCl [1]. 

Mercuric acetylide HgC2 forms when passing acetylene through Nessler reagent solution (solution of Hgl2 in KI and KOH). The product consists of a white flocculent precipitate identified by Keiser as HgC2 [15, 63] and later confirmed by X-ray analysis [62], However, on the basis of subsequent analysis, Fedoroff and Sheffield identified the reaction product as 3HgC2-H20 [2]. 

The effect of the type of mercuric reactant and composition of the reaction mixture on the yield of mercuric acetylide has been dealt with by Plimpton and Travers. Freshly precipitated mercuric oxide is suggested as the most appropriate starting material. It is dissolved in ammonia and, after ammonium carbonate addition. 

Burkard later tried to clarify the issue of the product composition and based on the results of elemental analysis concluded that the substance is mercurous acetylide monohydrate—Hg2C2-H20 [65]. Another not very well described way for preparing mercurous acetylide is the reaction of cuprous acetylide in aqueous suspension with mercurous nitrate [48]. Both preparation methods must be also carried out in the absence of daylight. 

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