Nickel-alkynyl complexes

The Kumada/Ishikawa group also investigated thermolytic reactions of alkynyl-polysilanes and silacyclopropenes in the presence of nickel catalysts and implicated a 1-silaallene-nickel complex as an intermediate in the reaction pathway... 

The metal centres in the iron, ruthenium, and osmium alkynyl complexes listed in Table 1 possess 18 valence electrons. Table 2 contains HRS data at 1.064 p,m and two-level-corrected values for similar 18 valence electron alkynyl and chloro nickel complexes, and a particularly efficient example is illustrated in Figure 5. These data are substantially resonance enhanced, although the relative orderings are maintained with two-level-corrected values. 

CaldweU LM, HUl AF, Hulkes AG, McQueen CMA, White AJP, WUliams DJ. Alkynyl selenolate complexes of iron, nickel, and molybdenum. Organometallics. 2010 29 6350-6358. 

Alkynyl complexes, which contain the grouping M—C=CR, are often more stable than the corresponding alkyls and aryls. An example is the nickel complex (Et3P)2Ni(C=CPh)2, wtiich melts at 149-15rc without decomposition. Alkynyl complexes are formally similar to metal cyanides and metal carbonyls. The species C=CR, CN and CO are all isoelectronic and presumably bond to a transition metal in a similar manner. All three ligands would be expected to possess both a-donor and ir-acceptor... 

Alkynyl complexes, M—C== CR, are more stable than the corresponding alkyk or aryls and the order R = alkyl < phenyl < ortAo-substituted phenyl alkynyl is found [37]. Examples are the nickel complexes (Et3P)2Ni(C=CR)2 where R = H, m.p. 36-36-5°, or Ph, 149-151°, which melt without decomposition, and (PEt3)2Pd(C=CPh)2, m.p. 162-164° d, which is more stable than the diphenyl analogue. The phenylethynyl com-... 

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

Alkynyl enals cyclize on treatment with a stoichiometric amount of Ni(COD)2/TMEDA complex to give nickel enolates such as 193,436>436a These metallacycles react with electrophiles including methyl iodide and benzaldehyde to yield cyclopentenol derivatives (Scheme 91). 

Surprisingly, there appear to be no examples of relevant nickel alkenyl compounds in the literature, nor is there any apparent reference to their unsuccessful pursuit. A single report describes the synthesis of an alkynyl complex, viz. the four-coordinate TplPr2Ni(C=CC02Me) (55),33 which was... 

Reaction of (diisopropylamino)chloroboryl ethers of alkynols (57) with alkynyl-stannanes (58) in the presence of nickel catalysts has been reported to afford formal f/ms-alkynylboration products (60), which could undergo the Suzuki-Miyaura coupling with organic halides. The 2-borylalkenylnickel(II) complex (59) was isolated as an intermediate in a reaction of the chloroboryl ether (57) with 1 equiv. of a nickel(0)-phosphine complex and characterized by X-ray crystallography.61... 

The synthesis of complex polycyclic molecules has been achieved by Montgomery et al. by cascade cyclization processes involving nickel enolates [40]. Up to three cycles could be generated in the intramolecular version of the reaction. Alkynyl enal or enone were first converted into their corresponding seven-membered cyclic enolates in the presence of Ni(cod)2/TMEDA [41 ]. These species could be trapped by electrophiles such as aldehydes. For example, upon treatment with the nickel catalyst, dialdehyde 32 afforded spiro-cycle 35 in 49% yield as a single diastereomer (Scheme 17). 

Reaction with an amine, AIBN, CO and a tetraalkyltin catalyst also leads to an amide.Benzylic and allylic halides were converted to carboxylic acids electroca-talytically, with CO and a cobalt imine complex. Vinylic halides were similarly converted with CO and nickel cyanide, under phase-transfer conditions.Allylic (9-phosphates were converted to allylic amides with CO and ClTi=NTMS, in the presence of a palladium catalyst. Terminal alkynes were converted to the alkynyl ester using CO, PdBr2, CuBr2 in methanol and sodium bicarbonate. ... 

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