Phosphinates alkynes

Dessy etal 629 632> have systematically studied the electrochemical redox behavior of more than 200 organometallic compounds with various ligands (phosphines, alkynes, CO, cydopentadiene) covering the metals of all main groups and the transition metal series. Their reduction can be rationalized by the following general scheme (Eq. (278) ) ... 

Other Pt" and Pt° complexes were used as catalysts for the hydrosilylation, e. g., PtCl2L2 and Pt2Cl4L2 (where L = olefin, nitrile, phosphine, alkyne, etc.) Pt salts and complexes with alkadienes, norbomadienes, and cycloolefins as well as phosphine complexes of Pt° [1-5]. The presence of phosphine ligands protects against colloid formation. 

Scheme 30 Lithium-catalyzed hydrophosphination/oligomerization of a secondary phosphine/ alkyne...

H.J. Bestmann and R. Zimmerman, Phosphine alkynes and ylids in G.M. Kosolapoff and L. Maier, Eds., Organic Phosphorus Compounds, Vol. 3, Wiley, New York, 1973. 

The hydrid phosphine-alkyne, bis(diphenylphosphino)ethyne, reacts with [W(CO)3(S2CNEt2)2] to give orange [W(CO)2(Ph2PC2PPh2)(S2CNEt2)2],... 

In the coupling of the allenyl ester 7 with a terminal alkyne, an electron-deficient phosphine (Ph3P) gave the enyne-conjugated ester 8 as the major product, while an electron-rich phosphine (TDMPP or TTMPP) yielded the non-conjugated enyne esters ( )- and (Z)-9[4],... 

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). 

Reaction of benzonitrile A-oxide with alkynic phosphinate (343) gave exclusively 5-phosphinylisoxazole (344), whereas reaction with enamine phosphinate (345) gave the otherwise inaccessible 5-unsubstituted 4-phosphinylisoxazole (346) (80JOC529). 

The bulk of derivatives are obtained by the displacement of CO by other ligands. These include phosphines and other group 15 donors, NO, mer-captans and unsaturated organic molecules such as alkenes, alkynes and cyclopentadienyls. 

The diiridium complex [Ir(CO)(PPh3)(/x-pz)]2 forms a diiridacyclobutene adduct of the type 143 with Me02CCsCC02Me, while the same reaction with F3CC=CCF3 leads to alkyne polymerization owing to dissociation of triphenyl-phosphine (85OM2106). 

Cationic phosphine ligands containing guanidiniumphenyl moieties were originally developed in order to make use of their pronounced solubility in water [72, 73]. They were shown to form active catalytic systems in Pd-mediated C-C coupling reactions between aryl iodides and alkynes (Castro-Stephens-Sonogashira reaction) [72, 74] and Rh-catalyzed hydroformylation of olefins in aqueous two-phase systems [75]. 

The diamagnetic ylide complexes 34 have been obtained from the reaction of electron-deficient complexes [MoH(SR)3(PMePh2)] and alkynes (HC=CTol for the scheme), via the formal insertion of the latter into the Mo-P bond. The structural data show that 34 corresponds to two different resonance-stabilized ylides forms 34a (a-vinyl form) and 34b (carbene ylide form) (Scheme 17) [73]. Concerning the group 7 recent examples of cis ylide rhenium complexes 36 cis-Me-Re-Me) have been reported from the reaction of the corresponding trans cationic alkyne derivatives 35 with PR" via a nucleophilic attack of this phosphine at the alkyne carbon. 

A related unprecedented double insertion of electron-deficient alkynes has also been reported in the reactions of the linear Pt2Pd heterotrimetallic complex 64 with 65 (RO2CCSCR) (Scheme 24) [95,96]. A series of unsymmetri-cal A-frame clusters 68 has thus been obtained in which a first insertion of the alkyne takes place site-selectively into the Pt-Pd bond vs the Pt-Pt bond (66). After a zwitter-ionic polar activation of the resulting inserted alkene (67), a subsequent reaction with the phosphine unit of the dpmp allows one to obtain the products 68 via the nucleophilic migration of the terminal P atom from the Pd center to the CH terminal carbon (formation of the P-C bond). 

Beller and coworkers found in 2009 that alkynes react with amines under the CO pressure (20 bar) in the presence of catalytic amounts of [Fe3(CO)i2] to the corresponding succinimide in moderate to excellent yields (Scheme 35) [110]. Various terminal and internal alkynes and ammonia or primary amines are adaptable for this transformation. Furthermore, [Fe(CO)s] as an iron source showed high activity. The catalytic activity, however, decreased considerably when a phosphine ligand such as PPh3 and ( Bu)2P("Bu) was employed. 

The hydrosilylation of alkynes has also been studied using as catalysts Pt, Rh, Ir and Ni complexes. The improvement of the regioselectivity of the catalyst and the understanding of stereoelectronic factors that control it have been major incentives for the ongoing research. From numerous studies involving non-NHC catalysts, it has been established that there is a complex dependence of the product ratio on the type of metal, the aUcyne, the metal coordination sphere, the charge (cationic versus neutral) of the catalytic complex and the reaction conditions. In the Speier s and Karstedt s systems, mixtures of the thermodynamically more stable a- and -E-isomers are observed. Bulky phosphine ligands have been used on many occasions in order to obtain selectively P-f -isomers. 

The metal catalysed hydroboration and diboration of alkenes and alkynes (addition of H-B and B-B bonds, respectively) gives rise to alkyl- or alkenyl-boronate or diboronate esters, which are important intermediates for further catalytic transformations, or can be converted to useful organic compounds by established stoichiometric methodologies. The iyn-diboration of alkynes catalysed by Pt phosphine complexes is well-established [58]. However, in alkene diborations, challenging problems of chemo- and stereo-selectivity control stiU need to be solved, with the most successful current systems being based on Pt, Rh and An complexes [59-61]. There have been some recent advances in the area by using NHC complexes of Ir, Pd, Pt, Cu, Ag and Au as catalysts under mild conditions, which present important advantages in terms of activity and selectivity over the established catalysts. 

Chloroacylation of terminal aryl, alkyl or alkenyl alkynes [Le. the addition of RC(=0)-C1 across the CC triple bond] with aromatic acyl chlorides was catalysed by [IrCl(cod)(lPr)] (5 mol%) in good conversions (70-94%) in toluene (90°C, 20 h). Z-addition products were observed only, hitemal alkynes were umeactive. Surprisingly, a phosphine/[lr(p-Cl)(l,5-cod)]2 system under the same conditions provides decarbonylation products (Scheme 2.34) [117]. 

The reaction of silylboranes 88 or germylborane 89 with a large excess of terminal or internal alkynes in the presence of a free-phosphine Ni-catalyst in situ generated... 

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