Iodination of alpha-phosphino enolate complexes of palladium(II) and platinum(II). Synthesis and crystal structures of [(dmba)Pd{Ph(2)PC(I)center dot center dot C(center dot center dot O)Ph}] and of the dipalladium(II) complex [(dmba)Pd{Ph(2)PC center dot center dot C(center dot center dot O)Ph}Pd(I)(tmeda)] obtained by palladium(0) insertion into the carbon-iodine bond

Electrophilic attack of 1 equiv of I-2 on a PCsp2 carbon of the Pt(II) complex cis-[Pt{Ph(2)PCH(sic)C((sic)O)Ph}(2)] (1) afforded cis- [Pt(I)[Ph(2)PCH(sic)C((sic)O)Ph}{Ph(2)PCH(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{Ph(2)PCH(sic)C((sic)O)Ph}{Ph(2)PC (I)(sic)C((sic)O)Ph}] (3). This alpha-phosphino, alpha-iodo enolato complex was obtained directly and quantitatively by the reaction of 1 with 1 equiv of N-iodosuccinimide (NIS). When 2, equiv of MS was used, the symmetrical complex cis-[Pt{Ph(2)PC(I)(sic)C((sic)O)Ph}(2)] (4) was formed selectively. In contrast to I-2, NIS was also able to functionalize the phosphino enolate ligand of complexes [(C N)Pd(Ph(2)PCH(sic)C((sic)O)Ph}] to give the corresponding iodo derivatives [(C N)Pd{Ph(2)PC(I)(sic)C((sic)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(Ph(2)PCH(sic)C((sic)O)Ph}(2)] or with [Ni(Ph) {Ph(2)PCH(sic)C((sic)O)Ph}(PPh(3))] were unsuccessful. Reaction of 5 with Pd(dba)(2) in the presence of tetramethylenediamine (tmeda) or 2,2'-bipyridine (bipy) afforded [(dmba)Pd{Ph(2)PC(sic)C((sic)O)Ph}Pd(I)(tmeda)] (7) and [(dmba>Pd{Ph(2)PC(sic)C((sic)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 P2(1)/n with Z = 4 in a unit cell of dimensions a = 12.867(3) Angstrom, b = 10.625(3) Angstrom, c = 19.509(6) Angstrom, and beta = 102.23(2)degrees; 7 . CH2Cl2 crystallizes in the monoclinic space group C2/c with Z = 8 in a unit cell of dimensions a = 35.906(3) Angstrom, b = 13.565(3) Angstrom, c = 15.775(2) Angstrom, and beta = 95.099(10)degrees. Complex 7 contains two palladium(Il) centers, in a square-planar environment, connected by the P-C unit of a phosphino enolate ligand which adopts an unprecedented mu-eta(2)(P,C):eta(2)(P,O) bonding mode. The two coordination planes are almost orthogonal and make a dihedral angle of 88.0(2)degrees, which minimizes the steric hindrance between the ligands.