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

The chemoselective reactivity of metal-coordinated phosphino enolates has been studied by the reactions of cis -[Ni{R‘ 2 PCH C( O)R} 2 ] (R = Ph, p -C 6 H 4 Me, Me; R‘ = Ph, i Pr, not all combinations) and [(C N)Pd{Ph 2 PCH C( O)Ph}] (C N = o -C 6 H 4 CH 2 NMe 2, dmba or C 10 H 8 N, 8-mq) with different metal electrophiles. In the reaction of cis -[Ni{Ph 2 PCH C( O)Ph} 2 ] ( 1a ) with [PtCl 2 (COD)] (COD = 1,5-cyclooctadiene), a transmetalation of the P,O ligands was observed, yielding the known complex cis -[Pt{Ph 2 PCH C( O)Ph} 2 ] ( 3 ). However, reaction of cis -[Ni{R‘ 2 PCH C( O)R} 2 ] with anhydrous CoI 2 afforded the heterobinuclear complexes cis -[Ni{R‘ 2 PCH C( O)R} 2 ]CoI 2 ( 5a, R = Ph, R‘ = Ph; 5b, R = p -C 6 H 4 Me, R‘ = Ph; 5c, R = Me, R‘ = Ph; 7, R = Ph, R‘ = i Pr) which contain the phosphino enolate ligand in an unusual chelating-bridging μ-η 1 ( O ):η 2 ( P,O ) coordination mode in a nonplanar NiO 2 Co unit. The magnetic properties of these complexes are discussed. The SHOP-type catalyst [Ni(Ph){Ph 2 PCH C( O)Ph}(PPh 3 )] also behaved as an oxygen-donor metalloligand toward CoI 2 to give a paramagnetic Co(II) complex. In contrast, reaction of [(C N)Pd{Ph 2 PCH C( O)Ph}] with [Au(PPh 3 )] + occurred with formation of [(dmba)Pd{Ph 2 PCH(AuPPh 3 )C(O)Ph}](BF 4 ) ( 4a ) in which a C enolate −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 1 H NMR spectroscopy. The solid state structures of complexes 4a · 1 / 2 C 7 H 8 and 5b ·CH 2 Cl 2 have been determined by single-crystal X-ray diffraction: 4a · 1 / 2 C 7 H 8 crystallizes in the triclinic space group P 1̄ 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 ·CH 2 Cl 2 crystallizes in the monoclinic space group P 2 1 / 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 / 2 C 7 H 8 ) and 3644 ( 5b ·CH 2 Cl 2 ) observed reflections to R and R w values of 0.0363 and 0.0406 ( 4a · 1 / 2 C 7 H 8 ) and 0.040 and 0.038 ( 5b ·CH 2 Cl 2 ), respectively.