Iodination of alpha-Phosphino Enolate Complexes of Palladium(II) and Platinum(II). Synthesis and Crystal Structures of [(dmba)Pd{Ph(2)PC(I)C(O)Ph}] and of the Dipalladium(II) Complex [(dmba)Pd{Ph(2)PCC(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 PC(sp)2 carbon of the Pt(II) complex (1) afforded (2) in 90% yield. Complex 2 was subsequently deprotonated by NaOEt in ethanol to give the bis(enolato) complex (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 NIS was used, the symmetrical complex (4) was formed selectively. In contrast to I(2), NIS was also able to functionalize the phosphino enolate ligand of complexes to give the corresponding iodo derivatives (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 or with were unsuccessful. Reaction of 5 with Pd(dba)(2) in the presence of tetramethylenediamine (tmeda) or 2,2'-bipyridine (bipy) afforded (7) and (8), respectively. The solid state structures of complexes 5 and 7.CH(2)Cl(2) 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) Å, b = 10.625(3) Å, c = 19.509(6) Å, and beta = 102.23(2) degrees; 7.CH(2)Cl(2) crystallizes in the monoclinic space group C2/c with Z = 8 in a unit cell of dimensions a = 35.906(3) Å, b = 13.565(3) Å, c = 15.775(2) Å, and beta = 95.099(10) degrees. 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 &mgr;-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.
Andrieu
Jacques
J
Laboratoire de Chimie de Coordination, Associé au CNRS (URA 416), Université Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg Cédex, France, and Laboratoire de Cristallographie et Modélisation des Matériaux Minéraux et Biologiques, Associé au CNRS (URA 809), Université Henri Poincaré Nancy 1, B.P. 239, F-54506 Vandoeuvre-les-Nancy Cédex, France.
Braunstein
Pierre
P
Dusausoy
Yves
Y
Ghermani
Nour Edine
NE