N-Alkynes

From the energetically preferred n-alkyne complex there is an alternative pathway involving the hydride ligand (Figure 5). The first step is an easy (AE = 6.6 kcal.mol 1) migratory insertion of the C=C triple bond into the cis Ru-H bond to yield a a-vinyl complex, A, 10.4 kcal.mol 1 below the it-alkyne complex. This 14-electron o-vinyl complex has also a saw-horse... 

Alkenes (unsaturated hydrocarbons with double bonds) are the oldest and most studied carbon ligands, with interest in their study dating from around 1827 [3,185-189]. An important aspect is the structure of 71-alkene and similar n-alkyne complexes. Their structural data is summarized in reviews [186-189] and presented in... 

The reduction of m ,m -(isodiCp)2TiCl2 with magnesium or LiBu affords the corresponding monochloro Ti(m) derivative, while the reduction with an excess of magnesium in the presence of bis(trimethylsilyl)ethylene (btmsc) gives the Ti(n)-alkyne complex.1111... 

Phosphines, as nucleophiles, add to many unsaturated substrates giving metallated ylides. Scheme 17 collects some representative examples of the addition of phosphines to carbyne complexes, giving (57) [132], to allenylidenes (58) [133], rr-alkenyls (59) [134], or CT-alkynyls (60) [135]. Moreover, reaction of phosphines with jt-aUcenes [136] and n-alkynes (61)-(64) [137-140] have also been reported. It is not possible to explain in depth each reaction, but the variety of resulting products provides an adequate perspective about the synthetic possibilities of this type of reactions. 

S.8.2.7.6. a-Alkenyl Complexes by Nucleophilic Attack on n-Alkyne- and Allene-Metal Complexes. 

The magnitude of coordinative distortions can be taken as an indication of the importance of the above-mentioned bonding components [5]. We can illustrate three extreme situations with complexes 12-14 (Scheme 4-4). Thus, the alkyne unit in 12, the first lan-thanide-alkyne n-complex [6], shows very little distortion from the free ligand (a = 177.4°, / = 1.15 A vs. 1.21 A in free butyne), consistent with nearly exclusive contribution from n (alkyne) M and minimal backbonding (the metal is d°) the rare main group-alkyne... 

Our story begins with a family of compounds we refer to as the [iVJpericyclynes [7, 8] a name intended to capture the structural essence of molecules composed of N alkyne units distributed symmetrically around the perimeter of a cycle with TV vertices (Fig. 9-2). Hydrocarbon 1 would be called [3]pericyclyne and represents the smallest member of the family. To preclude experimental complications arising from labile hydrogens on the carbon atoms between acetylenes in the parent molecules, we have generally appended methyl groups at the saturated centers. 

UnPHAs containing unsaturated monomers have been obtained from different bacteria (P. aeruginosa, P. putida, Pseudomonas oleovorans and Pseudomonas resinovorans) when cultured in media containing n-alkenes, n-alkynes, nnsaturated... 

Addition tO [CpFe(CO)(L)(n -alkyne)] (L = PPh, P(OPh)2) complexes occurs in a trans-fashion with a variety of nucleophiles (R, CN, SPh ) to give CpFe(CO)(L)(n -alkenyl) complexes which... 

With alkyne iodides, highly ordered SAMs having packing densities and molecular chain orientations very similar to those of alkanethiolates on Au(lll) can be prepared by reaction of terminal n-alkynes HC = C(CH2) CHj, n = 5, 7, 9, and 11 withAu(lll)at60°C[451]. 

Woycicki, W. Rhensius, P. Excess enthalpies of binary mixtures containing unsaturated hydrocarbons. 3. n-AUcane + n-alkyne and tetrachloromethane + n-alkyne J. Chem. Thermodyn. 1979,11,153-158... 

CpM(C0)2Co2(C0)g(u3-CPh)] (M=Fe, Ru). The interaction of ethyne with a Ptdn) surface has been modelled by reaction of ethyne with [Pt3(u3-H)(u-dppm)3) forming (140) via an intermediate n -alkyne complex. 

Otsa, E. Kiiyanen, I. Kudryavtseva, L. Measurement and ealculation of vapor-liquid equilibria in systems containing n-alkynes [Russ]. Eesti NSV Tead. Akad. Toim., Keem. 1979, 28, 113-121. 

Cycloaromatization of enediynes by diradical pathways in the thermal-and metal-catalyzed routes allows nonfunctionalized benzene derivatives to be prepared. The aromatization of enediynes by the action of nucleophiles produces aromatic compounds retaining the respective nucleophilic residue [333, 334]. The ruthenium-catalyzed reaction gives rise to the synthesis of various functionalized benzene derivatives. Thus, adding water, alcohols, aniline, acetylacetone, pyrroles, and dimethyl malonate to acyclic and aromatic enediynes 3.711 at 100°C for 12-24 hours in the presence of TpRuPPh3(MeCN)2PF6 (10 mol%) led to the functionalized benzenes 3.712 in satisfactory yields (Scheme 3.79) [334]. This cyclization involves regioselective nucleophilic attack of enediyne 3.711 to form a, TT-vinylruthenium intermediate 3.714 which finally converts to the benzene derivative. Experiment with labeled hydrogen atoms showed that the ruthenium n-alkyne complexes 3.713 are catalytically active. 

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