Acetylene complexes preparation

Olefin and acetylene complexes of Au(I) can be prepared by direct iateraction of the unsaturated compounds with a Au(I) hahde (190,191). The resulting products, however, are not very stable and decompose at low temperatures. Reaction with Au(III) hahdes leads to halogenation of the unsaturated compound and formation of Au(I) complexes or polynuclear complexes with gold ia mixed oxidatioa states. 

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. 

Generation of an Acetylene-Titanium Alkoxide Complex, Preparation of (Z)-1,2-Dideuterio-1 -(trimethylsilyl)-l -hexene. 

Unlike zirconium, the group IV metal titanium does not form the hydrometalation product but rather a (r -C5Q)-complex. The first titanium-fullerene complex 1 was prepared by reaction of the bis(trimethylsilyl)-acetylene complex of titanocene with equimolar amounts of Cjq (Scheme 7.1). 

In a study Rh-catalyzed cycloaddition of unactivated substrates, specifically, vinylallenes and acetylenes, is described.656 Appropriate catalysts were selected on the basis of a study of the bonding interactions of the reactants and transition metals. For this reaction a complex prepared in situ from [Rh(COD)2]OTf and P[OCH(CF3)2]3, one of the most strongly electron-accepting ligands available, was used. Under the conditions applied, even ethylene, one of the most sluggish... 

The only other report (88) of a gold(I) acetylene complex concerns [AuBr(cyclooctyne)2], which was prepared from aurous bromide and cy-clooctyne. 

Reversible adsorption and desorption of the acetylene is possible under suitable conditions. However, using the corresponding low molecular weight manganese complexes such as MeCpMn(CO)3 and CpMn(CO)3 (Cp = cyclopentadienyl ring), the acetylene complex could hardly be prepared due to instability of the acetylene complex. 

Photochemical reactions have been used for the preparation of various olefin, and acetylene complexes (7). Application to the coordination of dienes as ligands has not been used extensively, so far. In this article the preparative aspects of the photochemistry of carbonyls of the group 6 and group 7 elements and some key derivatives, with the exception of technetium, with conjugated and cumulated dienes will be described. Not only carbonyl substitution reactions by the dienes, but also C—C bond formation, C—H activation, C—H cleavage, and isomerizations due to H shifts, have been observed, thereby leading to various types of complexes. 

The field of acetylene complex chemistry continues to develop rapidly and to yield novel discoveries. A number of recent reviews 1-10) covers various facets including preparation, structure, nature of bonding, stoichiometric and catalytic reactions, and specific aspects with particular metals. The first part of this account is confined to those facets associated with the nature of the interactions between acetylenes and transition metals and to the insertion reactions of complexes closely related to catalysis. Although only scattered data are available, attempts will be made to give a consistent interpretation of the reactivities of coordinated acetylene in terms of a qualitative molecular orbital picture. 

Difficulties arise when the most simple ynediamine bis(dimethylamino)acetylene is prepared starting with trichloroethylene since dimethylamine may react further giving tris(dimethylamino)ethylene 163). A simple one-pot procedure for this ynamine has been elaborated in which trichloroethylene is treated with sodium amide and dimethylamine under normal pressure. The average yield is about 60 %163). Di-chloroacetylene ether complex can now be prepared under phase-transfer (PT) conditions from trichloroethylene. It reacts with dimethylamine under PT conditions to N,N,N"N -tetramethylglycinamide apparently via the ynediamine intermediate 164). 

J. Chatt, and L. A. Duncanson, Infrared Spectra and Structure Attempted Preparation of Acetylene Complexes, J. Chem. Soc. 1953, 2939-2947. 

GENERATION OF AN ACETYLENE-TITANIUM ALKOXIDE COMPLEX PREPARATION OF (Z)-l,2-DIDEUTERIO-l-(TRIMETHYLSILYL)-l-HEXENE... 

Wakatsuki and co-workers 287) have prepared vinyl ether complexes of Pd(II) and Pt(II) of composition [CI2ML] (M = Pd or Pt L = vinyl ethers, propenyl ethers, 1,2-dimethoxyethylene) by displacement of PhCN from Pd(PhCN)2Cl2- They are fairly stable at 25°C. Since these ethers would be good a donors but poor tt acceptors, the stability of these complexes suggest that a donation is most important with tt complexes of Pd(II) and Pt(II). This conclusion is in agreement with earlier IR studies, as well as a recent NMR study of Pt olefin and acetylene complexes 35). Furthermore, a study of complex formation... 

The configuration of the acetylene group was inverted through an acetylene-cobalt complex prepared by treatment of the acetylene with Co2(CO)g (O Scheme 31) [52]. Upon treatment of the complex with acid, epimerization occurred via a propargylic cation intermediate stabilized by the cobalt complex to afford the thermodynamically more stable -C-glycoside as the... 

Chart J, Duncanson LA (1953) Olefin coordination compounds. Part III. Infrared spectra and structure attempted preparation of acetylene complexes. 1 Chem Soc 2939... 

Titanium—acetylene complexes react with allylic or propargylic halides or acetates through regioselective titanacycle formation and subsequent fl-elimination [36,37]. The reaction therefore provides a convenient method of preparing 1,4-alkadienes, including those bearing functional groups as exemplified in Eq. 9.16 [38]. 

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