The synthesis of palladacyclopentadienyl derivatives from rigid bis-alkynes and their use as precursors in the synthesis of fluoroanthene-like cycles under mild conditions. A reactivity investigation

Abstract

The palladium (0) The reactions of unsaturated molecules catalyzed by palladium complexes represent an important topic in organometallic chemistry and consequently a wealth of papers have been recently published in this interesting field [1]. Moreover, exhaustive investigations on the attack of some dissymmetrically and symmetrically substituted alkynes on palladium(0) olefin derivatives to give the corresponding palladacyclopentadienyl complexes were recently carried out by Elsevier's group [2] and in our laboratory .In the latter case, the related mechanism was proposed on the basis of structural and kinetic evidence [3].In particular, the alkynes used had the general structure ZC"CZ (Z@COOMe, COOEt, COOt-Bu) and their reactivity was found to be strongly related to their steric hindrance as can be expected in the case of an associative alkyne attack. Thus, we decided to decrease the molecular degrees of freedom by linking together two alkyne groups in hopes that this approach could represent a further step toward the synthesis of novel cyclopalladate compounds which might eventually collapse into new condensed polycyclic compounds. We have therefore synthesized the diynes 1,8-bis(methylpropynoate)naphthalene 1 and 2,2 0 -bis(methylpropynoate)biphenyl 1 0 and studied their reactivity toward olefin palladium(0) derivatives 2 to give the corresponding palladacyclopentadienyl complexes 3 (Chart 1).The electron-deficiency of the alkyne -a prerequisite for the quantitative oxidative coupling toward palladium(0) olefin complexes -is obtained, in the case of the bis-alkyne 0022-328X/$ -see front matter Ó

Synthesis, stability and reactivity of palladium(0) olefin complexes bearing labile or hemi-labile ancillary ligands and electron-poor olefins

“…Mechanism of formation of a metallacyclopentadiene by addition of an alkyne to palladium olefin derivatives involving naked palladium as intermediate. A peculiar application of the addition of alkynes to palladium(0) derivatives is represented by the kinetic study of the reaction of rigid bis-alkynes moiety with palladium(0) complexes [77]. The cyclopalladate formed might represent a valuable precursor for the synthesis of fluoranthene-like cycles under mild conditions (Scheme 12).…”

Transmetalation reactions. The role of the stabilizing olefin in determining the overall reaction rate

“…The complex was filtered off, washed with small aliquots of diethyl ether and dried under vacuum (0.077 g, yield 65% 184.0 (d, CO, J CP = 6.2 Hz CO trans-N); 165.6 (C, C 2 ); 151.5 (C, C 10 ); 151.2 (C, C 9 ); 138.3 (CH, C 4 ); 137.8 (CH, C 7 ); 134.3 (d, C, J CP = 35.1 Hz, C 8 ); 131.2 (CH, C b ); 131.0 (CH, C 5 ); 130.5 (CH, C b ); 126.3 (d, CH, J CP = 4.8 Hz, C 6 ); 125.4 (CH, C a ); 125.0 (CH, C a ); 123.8 (CH, C 3 ); 66.2 (d, CH, J CP = 21.0 Hz CH@CH trans-P); 62.6 (CH, CH@CH trans-N); 30.2 (CH 3 , quinoline-CH 3 ). 31 [24], 2Db, 2Eb [25], 2Ea [26] were prepared according to published procedures. Anal.…”

Nickel, palladium and platinum

“…95 The Pd(0) derivatives of the type [Pd(Z 2 -L 27 )(L 28 )] [L 27 = dimethyl fumarate, fumaronitrile, tetramethylethylenetetracarboxylate; L 28 = HNSPh, 2,2 0 -bipy, dppe] have been reacted with 1,8-bis(methylpropynoate)naphthalene and 2,2 0 -bis(methylpropynoate)biphenyl to give the corresponding cyclopalladate complexes [PdC 4 (COOMe) 2 (Ph) 2 (L 28 )]. 96 A short, facile, and high-yielding synthesis of to give the extremely efficient PCP pincer Suzuki catalyst [Pd (20)Cl], bearing aminophosphine substituents, has also been reported. 97 The reaction of PdCl 2 , dppm and CS 2 in CH 2 Cl 2 /MeOH has been shown to result in an unusual PCP carbodiphosphorane complex [Pd(kP,C,P 0 -{Ph 2 PCH 2 Ph 2 P} 2 C)Cl]Cl.…”