Stepwise Successive Insertion of Carbon Monoxide and Allenes into Palladium−Carbon Bonds of Complexes Containing the Rigid Bidentate Nitrogen Ligand Bis(p-anisylimino)acenaphthene

Abstract

Propadiene, 3-methyl-1,2-butadiene (DMA), and 2,4-dimethyl-2,3-pentadiene (TMA) reacted via migratory insertion with both neutral and ionic Pd(R)X(p-An-BIAN) (R = Me (1), C(O)Me (2); X = Cl (a), SO3CF3 (b)) complexes, containing the rigid nitrogen ligand bis(p-anisylimino)acenaphthene (p-An-BIAN), resulting in the novel and stable allylpalladium complexes Pd(η3-C3H4R)X(p-An-BIAN) (R = Me (3), C(O)Me (6)), Pd(η3-C5H8R)X(p-An-BIAN) (R = Me (4), C(O)Me (7)), and Pd(η3-C7H12R)X(p-An-BIAN) (R = Me (5), C(O)Me (8)), respectively (X = Cl (a), SO3CF3 (b)). The neutral complexes 6a and 7a reacted with carbon monoxide to form the acylpalladium complexes Pd(C(O)C3H4C(O)Me)Cl(p-An-BIAN) (9) and Pd(C(O)C5H8C(O)Me)Cl(p-An-BIAN) (10), respectively, while the analogous trifluoromethanesulfonate complexes 6b and 7b were completely inert toward CO. Complexes 9 and 10 reacted again with propadiene and DMA, respectively, to yield the allylpalladium complexes Pd(η3-C3H4C(O)C3H4C(O)Me)Cl(p-An-BIAN) (11) and Pd(η3-C5H8C(O)C5H8C(O)Me)Cl(p-An-BIAN) (12), respectively. Also insertion of norbornadiene in complex 10 was possible, yielding the ionic complex [Pd(C7H8C(O)C5H8C(O)Me)(p-An-BIAN)]Cl (13a), which reacted with AgSO3CF3 to give [Pd(C7H8C(O)C5H8C(O)Me)(p-An-BIAN)]SO3CF3 (13b). The novel complexes 9−12 are the first isolated and fully characterized complexes formed by successive insertion reactions of carbon monoxide and allenes, while 13a is the first isolated complex containing a metal-bonded ter-oligomer of carbon monoxide, an allene, and norbornadiene. The X-ray crystal structure of 7a has been determined and shows a distorted square pyramidal geometry in which the BIAN ligand is bonded to the palladium center in an unusual asymmetric fashion (Pd−N(1) = 2.144(7) Å; Pd−N(2) = 2.600(8) Å).

Insertions of Allenes into Palladium−Carbon Bonds of Complexes Containing Bidentate Nitrogen Ligands. Structural and Mechanistic Studies

“…The Pd-(1)-N(11) distance of 2.115(7)Å is comparable to the ones measured for both the cationic complex [(Bipy)Pd-{(1-3-η)-2-benzyl-propenyl}](BF 4 ) 25 and the neutral complexes (2,9-dimethyl-1,10-phenanthroline)Pd{(1-3-η)-3-methyl-2-butenyl}Cl 51 and (p-An-BIAN)Pd{(1-3-η)-2-acetyl-3-methyl-2-butenyl}Cl. 33 The Pd(1)-C(11) distance of 2.367(2) Å appears rather short as compared to the analogous distances in the above mentioned neutral complexes, which are 2.405(3) and 2.451(3) Å, respectively. The allyl fragment is symmetrically bonded to palladium with Pd(1)-C(116) ) 2.086(10) Å and Pd-(1)-C(117) ) 2.098(10) Å.…”

“…Additionally, cooligomerization of CO and allenes using a palladium complex containing the Ar-BIAN ligand has been demonstrated to be possible, analogous to the cooligomerization of CO and norbornadiene. 33 To obtain more insight into the mechanism of the allene insertion reaction, we will present in this article a kinetic study on allene insertions into the Pd-R bond of (NkN)Pd(R)X complexes in which NkN are bidentate nitrogen ligands and R represents the acyl and methyl groups.…”

Methyl-, acetyl- and allyl-palladium and -piatinum complexes containing the novel chiral phosphorus-imine 2-(diphenylphosphino)-benzylidene-S( − )-α-methyl-benzylamine ligand

“…Recently reported insertions of (substituted) allenes into the methylpalladium bond of [PdX(Me) (N-N)] [32,33] prompted us to study the insertion of allenes into the Pd-R bond of [ PdX(Me ) (PN) ] complexes. Since these insertions were found to proceed very slowly (after ~wo weeks only 60% of 7a was converted to 13a) and since we are interested in the structural features of allylpalladium complexes with the chiral PN ligand in comparison with the N--S complexes [34], we decided to prepare The downfield 31p{ tH} NMR resonance shifts (30 < A 8 31p{tH} <40 ppm) and the upfield shift of the IH imine proton ( 0.01 < A 8 ~H < 0.73 ppm) of the PN ligand observed for almost all allylpalladium complexes, when compared to those values found in the free ligand, indicate a chelate bonded ligand in solution, which is corroborated by condtmtivity experiments in CH3OH (Section 2).…”

Synthesis of novel heteroditopic carbene–pyridine palladium(II) chloro vinyl complexes. Comparative reactivity of different palladium vinyl derivatives toward transmetalation with alkynyl stannane

“…Among different types of spectator ligands used in catalysis, nitrogen heterocyclic carbenes (NHCs) have acquired an increasing importance thanks to the stability to air and moisture that these ligands impart to their derivatives. Consequently the complexes with NHC as ancillary ligands are often preferred to those bearing phosphine [3].The insertion of unsaturated molecules through the Pd\C bond represents an important step in cross-coupling [4] and co-polymerization reactions [5]. In the past we have been involved in the study of insertion of alkynes in methyl complexes of Pd(II) bearing pyridylthioether as ancillary ligands giving vinyl derivatives [6].…”

“…The insertion of unsaturated molecules through the Pd\C bond represents an important step in cross-coupling [4] and co-polymerization reactions [5]. In the past we have been involved in the study of insertion of alkynes in methyl complexes of Pd(II) bearing pyridylthioether as ancillary ligands giving vinyl derivatives [6].…”