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Reactivity of α-Phosphino Enolate Complexes of Nickel(II) and Palladium(II) toward Electrophilic Metal Centers. Synthesis and Crystal Structures of the Bimetallic Palladium(II)−Gold(I) Complex [(dmba)Pd{Ph2PCH(AuPPh3)C(O)Ph}](BF4) and of the Nickel(II)−Cobalt(II) Paramagnetic Complex cis-[Ni{Ph2PCH C( O)(p-C6H4CH3}2]CoI2

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journal contribution
posted on 09.10.1996, 00:00 by Jacques Andrieu, Pierre Braunstein, Marc Drillon, Yves Dusausoy, Florent Ingold, Pierre Rabu, Antonio Tiripicchio, Franco Ugozzoli
The chemoselective reactivity of metal-coordinated phosphino enolates has been studied by the reactions of cis-[Ni{R‘2PCH C( O)R}2] (R = Ph, p-C6H4Me, Me; R‘ = Ph, iPr, not all combinations) and [(C N)Pd{Ph2PCH C( O)Ph}] (C N = o-C6H4CH2NMe2, dmba or C10H8N, 8-mq) with different metal electrophiles. In the reaction of cis-[Ni{Ph2PCH C( O)Ph}2] (1a) with [PtCl2(COD)] (COD = 1,5-cyclooctadiene), a transmetalation of the P,O ligands was observed, yielding the known complex cis-[Pt{Ph2PCH C( O)Ph}2] (3). However, reaction of cis-[Ni{R‘2PCH C( O)R}2] with anhydrous CoI2 afforded the heterobinuclear complexes cis-[Ni{R‘2PCH C( O)R}2]CoI2 (5a, R = Ph, R‘ = Ph; 5b, R = p-C6H4Me, R‘ = Ph; 5c, R = Me, R‘ = Ph; 7, R = Ph, R‘ = iPr) which contain the phosphino enolate ligand in an unusual chelating-bridging μ-η1(O):η2(P,O) coordination mode in a nonplanar NiO2Co unit. The magnetic properties of these complexes are discussed. The SHOP-type catalyst [Ni(Ph){Ph2PCH C( O)Ph}(PPh3)] also behaved as an oxygen-donor metalloligand toward CoI2 to give a paramagnetic Co(II) complex. In contrast, reaction of [(C N)Pd{Ph2PCH C( O)Ph}] with [Au(PPh3)]+ occurred with formation of [(dmba)Pd{Ph2PCH(AuPPh3)C(O)Ph}](BF4) (4a) in which a Cenolate−Au bond has been formed while the P,O chelate has remained coordinated to palladium. This reaction generates a new stereogenic center, as also evidenced by 1H NMR spectroscopy. The solid state structures of complexes 4a·1/2C7H8and 5b·CH2Cl2 have been determined by single-crystal X-ray diffraction:  4a·1/2C7H8 crystallizes in the triclinic space group P1̄ with Z = 2 in a unit cell of dimensions a = 16.778(4) Å, b = 14.269(5) Å, c = 10.838(6) Å, α = 79.27(4)°, β = 71.59(3)°, and γ = 72.68(2)°; 5·CH2Cl2 crystallizes in the monoclinic space group P21/n with Z = 4 in a unit cell of dimensions a = 12.940(1) Å, b = 18.329(2) Å, c = 18.495(2) Å, and β = 91.627(8)°. The structures have been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least-squares methods on the basis of 7240 (4a·1/2C7H8) and 3644 (5b·CH2Cl2) observed reflections to R and Rw values of 0.0363 and 0.0406 (4a·1/2C7H8) and 0.040 and 0.038 (5b·CH2Cl2), respectively.