Stereospecific polymerization of 1,3-butadiene catalyzed by cobalt complexes bearing N-containing diphosphine PNP ligands

The sterically bulky pyridinyl phosphine (P∼N) ligands have been prepared from the phosphinylation of 2,4-di-tert-butyl-6-methylpyridine. Due to the steric hindrance, substitution reaction of these P∼N ligands with (COD)PdMeCl yields the chloro-bridged dipalladium species [(P∼N)2Pd2Me2Cl2], in which the P∼N ligand acts as a monodentate. Treatment of these dimeric palladium compounds with AgBF4 in the presence of acetonitrile gives the corresponding C–H activation metal complex [(P∼N∼C)Pd(CH3CN)]BF4. Both spectral and X-ray single-crystal characterization of these palladium complexes are presented.

New bulky phosphinopyridine ligands. P∼N∼C tridentates in palladium complexes

Novel rhodium complexes containing a bulky iminophosphine ligand and their use as catalysts for the hydroboration of vinylarenes

The new selenoether functionalised tertiary phosphines (2-Ph2P)C6H4C(H)N(CH2)nSePh (n = 3 1a; 4 1b) were readily prepared by condensation of (2-Ph2P)C6H4C(H)O and H2N(CH2)nSePh (n = 3, 4) in absolute ethanol. Reaction of two equiv. of Ph2PCH2OH with H2N(CH2)nSePh (n = 3, 4) affords the symmetrical ditertiary phosphines (Ph2PCH2)2N(CH2)nSePh (n = 3 2a; 4 2b). Reaction of 1a–2b with [MCl2(cod)]
(M = Pt, Pd) gave the dichlorometal(II) chelate complexes 3a–4d in which either six-membered P,P- or P,N-ligation is observed. Chloro bridge cleavage of [{RuCl2(p-cymene)}2] or tht (tht = tetrahydrothiophene) substitution of [AuCl(tht)] with 2a
(or 2b) gave the new complexes [{RuCl2(p-cymene)}2{μ-(P,P′-Ph2PCH2)2N(CH2)nSePh}]
(n = 3 5a; 4 5b) or [{AuCl}2{μ-(P,P′-Ph2PCH2)2N(CH2)nSePh}]
(n = 3 6a; 4 6b) in which the ligand P,P′-bridges two metal centres. Spectroscopic evidence suggests the pendant selenoether group in 3c undergoes further reaction with [PdCl2(MeCN)2] affording an unusual trinuclear palladium(II) complex 7. Furthermore reaction of 3b with 1 equiv. of Ag[BF4] in dichloromethane gave the cationic complex [PtCl(1a)][BF4]
8 in which 1a functions as a P,N,Se-tridentate ligand. All structures have been confirmed by a combination of spectroscopic, analytical and single crystal X-ray studies. The structure of 8 represents, to the best of our knowledge, an extremely rare example of a crystallographically characterised Group 10 metal complex with a P/N/Se/Cl coordination environment.

Michael J.R. Halstead

Papers

The reactivity of the ‘P2N’ ligand 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene]-benzeneamine towards sulfur and acid