Migratory insertion reactions of nickel and palladium σ-alkyl complexes with a phosphinito-imine ligand

Abstract

Ligand exchange reactions have been used for the synthesis of metallacyclic complexes of Ni and Pd of the type [M[upper bond 1 start](CH(2)CMe(2)-o-C(6)[upper bond 1 end]H(4))(P-N)], where P-N is the phosphinito-imine ligand P(iPr)(2)OC(Me)[double bond, length as m-dash]N(2,6-C(6)H(3)(iPr)(2). The protic acid [H(OEt(2))(BAr'(4))] (Ar' = 3,5-C(6)H(3)(CF(3))(2)) selectively cleaves one of the two σ metal-carbon bonds, affording cationic monoalkyl complexes. Nickel monoalkyls stabilized with Et(2)O or MeCN ligands are thermally unstable and spontaneously undergo a decomposition process that ultimately leads to the breakdown of the phosphinito-imine ligand. In contrast, cationic alkylpalladium derivatives are thermally very stable, allowing the isolation of a formally unsaturated monoalkyl complex stabilized by an intramolecular π-arene interaction. Although monoalkynickel and -palladium phosphinito-imine derivatives are inactive as ethylene polymerization or copolymerization catalysts, they readily experience migratory insertion reactions. A palladium chelate arising from the successive insertion of CO and ethylene has been isolated and characterized.

Insertion Reactions of Six-Membered Cyclopalladated N,N′,N″-Triarylguanidine, [Pd{κ2(C,N)-C6H3Me-3(NHC(NHAr)(═NAr))-2}(μ-Br)]2 (Ar = 2-MeC6H4) with PhC≡C—C(O)OR (R = Me and Et): A Gateway to Second Orthopalladation through Novel Rearrangements

“…Palladium complexes that possess η 2 arene have been characterized by single crystal X-ray diffraction. In these complexes, the Pd–C distance associated with the ipso carbon varies from 2.34–2.49 Å, and that associated with ortho carbon varies from 2.33–2.59 Å. ,, The Pd–C ipso distance in all complexes except two is shorter than the Pd–C ortho distance. , The minimum and the maximum difference between the Pd–C ipso and the Pd–C ortho distances in η 2 arene palladium complexes are 0.022 and 0.161 Å, respectively. Remarkably, one of the Pd–C ortho distances in 9a and 10a is shorter than the Pd–C ipso distance (Pd–C ortho : 2.301(3) Å ( 9a ), 2.312(3) Å ( 10a ); Pd–C ipso : 2.367(3) Å ( 9a ), 2.388(3) Å ( 10a )), which may be responsible for the proclivity of ortho -carbon of the coordinated phenyl ring to undergo intramolecular cyclopalladation as found in the conversion of 9a to 11a - d 3 .…”

Synthesis and Reactivity of Model Intermediates Proposed for the Pd-Catalyzed Remote C–H Functionalization of N-(2-Haloaryl)acrylamides

“…In an attempt to isolate an analogous complex to 10 , we carried out the partial protonolysis of the C­(sp 2 )–Pd bond (present in intermediate 4a ) by adding carefully a small amount of a saturated solution of HCl in CH 2 Cl 2 to a solution of 4a in CH 2 Cl 2 at room temperature (Scheme ). Via this method, we could isolate complex 11 , whose 31 P NMR spectrum showed a singlet at 37.8 ppm, very close to that of the complex 10 .…”

Nickel, palladium and platinum

“…19 The phosphinito-imine complexes [NiCl 2 (20) 2 ] also formed active ethylene oligomerization catalysts. 20 Fourteen derivatives of iminopyridyl-based ligands (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) were prepared. The corresponding [Ni (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)Br 2 ] complexes exhibited high activities (up to the range of 10 7 g mol À1 (Ni) h À1 ) towards ethylene polymerization, producing branched polyethylenes with narrow polydispersity.…”

“…20 Fourteen derivatives of iminopyridyl-based ligands (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) were prepared. The corresponding [Ni (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)Br 2 ] complexes exhibited high activities (up to the range of 10 7 g mol À1 (Ni) h À1 ) towards ethylene polymerization, producing branched polyethylenes with narrow polydispersity. 21 A series of bis(thiazolinyl)-and bis(thiazolyl)pyridine Ni(II) complexes were prepared (41)(42)(43)(44), as well as the four-coordinate bis(thiazolinyl) phenyl complex 45.…”

“…50) stabilized by an intramolecular p-arene interaction. 27 The Pd(II) and Ni(II) complexes of the N,O pyridinyloxazolidine ligand 51 were tested as catalysts in the conjugate addition of aliphatic amines to benzalacetone, giving moderate-to-high yields of conversion under mild conditions. 28 A series of Pd(II) and Ni(II) complexes of oxamide oximes (52) have been prepared.…”