184362-07-0Relevant academic research and scientific papers
Iodination of α-Phosphino Enolate Complexes of Palladium(II) and Platinum(II). Synthesis and Crystal Structures of [(dmba)Pd{Ph2PC(I)-C(-O)Ph}] and of the Dipalladium(II) Complex [(dmba)Pd{Ph2PC-C(-O)Ph}Pd(I)(tmeda)] Obtained by Palladium(0) Insertion into the Carbon-Iodine Bond
Andrieu, Jacques,Braunstein, Pierre,Dusausoy, Yves,Ghermani, Nour Edine
, p. 7174 - 7180 (2008/10/09)
Electrophilic attack of 1 equiv of I2 on a PCsp2 carbon of the Pt(II) complex cis-[Pt{Ph2PCH-C(-O)Ph}2] (1) afforded cis-[Pt(I)[Ph2PCH-C(-O)Ph}{Ph2PCH(I)C(O)Ph}] (2) in 90% yield. Complex 2 was subsequently deprotonated by NaOEt in ethanol to give the bis(enolato) complex cis-[Pt{Ph2PCH-C(-O)Ph}{Ph2PC (I)-C(-O)Ph}] (3). This α-phosphino, α-iodo enolato complex was obtained directly and quantitatively by the reaction of 1 with 1 equiv of N-iodosuccinimide (NIS). When 2 equiv of NIS was used, the symmetrical complex cis-[Pt{Ph2PC(I)-C(-O)Ph}2] (4) was formed selectively. In contrast to I2, NIS was also able to functionalize the phosphino enolate ligand of complexes [(C N)Pd{Ph2PCH-C(-O)Ph}] to give the correspending iodo derivatives [(C N)Pd{Ph2PC(I)-C(-O))Ph}] (C N = dmba (5) or 8-mq (6)). These represent the first examples in which a phosphino enolate C-H bond has been directly functionalized, i.e. replaced by a C-X bond. Attempts to use this procedure with cis-[Ni{Ph2PCH-C(-O)Ph}2] or with [Ni(Ph) {Ph2PCH-C(-O)Ph}(PPh3)] were unsuccessful. Reaction of 5 with Pd(dba)2 in the presence of tetramethylenediamine (tmeda) or 2,2′-bipyridine (bipy) afforded [(dmba)Pd{Ph2PC-C(-O)Ph}Pd(I)(tmeda)] (7) and [(dmba)Pd{Ph2PC-C(-O)Ph}Pd(I)(bipy)] (8), respectively. The solid state structures of complexes 5 and 7·CH2Cl2 have been determined by single-crystal X-ray diffraction: 5 crystallizes in the monoclinic space group P21/n with Z = 4 in a unit cell of dimensions a = 12.867(3) A, b = 10.625(3) A, c = 19.509(6) A, and β= 102.23(2)°; 7·CH2Cl2 crystallizes in the monoclinic space group C2/c with Z = 8 in a unit cell of dimensions a = 35.906(3) A, b = 13.565(3) A, c = 15.775(2) A, and β= 95.099(10)°. Complex 7 contains two palladium(II) centers, in a square-planar environment, connected by the P-C unit of a phosphino enolate ligand which adopts an unprecedented μ-μ2(P,C):η2(P,O) bonding mode. The two coordination planes are almost orthogonal and make a dihedral angle of 88.0(2)°, which minimizes the steric hindrance between the ligands.
