Chemoselective Reactions of the Phosphino Enolate Li[Ph2PCH C( O)NPh2] with Ph2P−Cl and M−Cl Bonds (M = Pd, Pt). Coordination Properties of the New Functional Diphosphine Ligand (Ph2P)2CHC(O)NPh2. Hemilabile Behavior of [Cu2{(Ph2P)2CHC(O)NPh2-P,P,O}2](BF4)2. Reactivity and Molecular Structure of [(8-mq)Pd{Ph2PCH C( O)NPh2}

Abstract

The functional phosphine Ph2PCH2C(O)NPh2 (L1) was obtained by P−C selective coupling of Ph2PCl with Li[CH2 C( O)NPh2] and we have studied the influence of the −NPh2 substituent on the reactivity of the corresponding enolate Li[Ph2PCH C( O)NPh2] toward Ph2P−Cl and M−Cl bonds (M = Pd, Pt). A selective P−C coupling reaction with Ph2PCl allowed the synthesis of the new diphosphine ligand (Ph2P)2CHC(O)NPh2 [bis(diphenylphosphino)-N,N-diphenylacetamide] (L2). The dicationic dinuclear complex [Cu2{(Ph2P)2CHC(O)NPh2-P,P,O}2](BF4)2 (3) has been obtained from the reaction of [Cu(NCMe)4](BF4) with L2. A preliminary X-ray diffraction study revealed a μ2-η3 tripod-like bonding for L2 in this centrosymmetric dimeric complex: each copper atom is P,O-chelated by one ligand and P-bonded to the other ligand. An eight-membered Cu2P4C2 ring is thus formed with the functional diphosphine ligand. The dynamic behavior has been studied in CHCl3 solution of mono- and binuclear copper(I) complexes of L1 and L2. Reversible oxygen-metal dissociation occurs in the presence of donor solvents such as NCMe or SMe2. The reaction of Li[Ph2PCH C( O)NPh2] with [(C N)Pd(μ-Cl)2] afforded the complexes [(C N)Pd{Ph2PCH C( O)NPh2}] [(9) (C N) = dimethylbenzylamine (dmba); (10) (C N) = 8-methylquinoline (8-mq)]. The molecular structure of [(8-mq)Pd{Ph2PCH C( O)NPh2}] has been determined by single-crystal X-ray diffraction: it crystallizes in the monoclinic space group P21/c with Z = 4 in a unit cell of dimensions a = 8.801(2) Å, b = 31.483(6) Å, c = 10.939(2) Å, β = 101.37(2)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares methods on the basis of 2863 observed reflections to R and Rw values of 0.0268 and 0.0338, respectively. A temperature dependence of the reaction of Li[Ph2PCH C( O)NPh2] with [PtCl2(NCPh)2] has been observed which leads to cis-Pt[Ph2PCH C( O)NPh2]2 (11) at −60 °C and to trans-Pt[Ph2PC{C(NH)Ph}{C(O)NPh2}]2 (12) at 0 °C. The high reactivity of cis-Pt[Ph2PCH C( O)NPh2]2 toward p-MeC6H4NCO leads to two diastereoisomeric products cis-Pt[Ph2PCH{C(O)N(p-MeC6H4)}{C(O)NPh2}]2 (16a,b in a 1:1 ratio), which contain new chiral heterodifunctional phosphines.