Reactions of trinuclear platinum clusters with electrophiles: ionisation isomerism with [Pt3(µ2-I)(µ-PPh2)2(PPh3)3]I and [Pt3(µ-PPh2)2I2(PPh3)3]. Structures of [Pt3(µ2-Cl)(µ-PPh2)2(PPh3)3]PF6, [Pt3(µ-PPh2)2I2(PPh3)3] and of the Pt-Ag cluster [Pt3{µ3-AgBF4}(µ2-I)(µ-PPh2)2(PPh3)3]BF4.

A reaction of the 44 electron cluster [Pt3(µ-PPh2)3Ph(PPh3)2] (1) with wet AgBF4 afforded the cationic cluster [Pt3(µ2-OH)(µ-PPh2)2(PPh3)3]BF4 (3(BF4)) which slowly transformed into [Pt3(µ2-Cl)(µ-PPh2)2(PPh3)3]BF4 (4(BF4)) upon recrystallization from CH2Cl2. These 44 electron clusters have been characterized by (31)P{(1)H} NMR, and the crystal structure of 4(PF6) has been determined by X-ray diffraction, as well as that of [Pt3(µ-PPh2)2I2(PPh3)3] (5), which was obtained by recrystallization of the known cluster [Pt3(µ2-I)(µ-PPh2)2(PPh3)3]I (2(I)) from toluene and represents a neutral formula isomer of the latter. In addition, we have prepared the adducts of cluster 1 containing the moieties [Cu(NCMe)2](+) and [Au(PPh3)](+) in 6 and 7, respectively, and on the basis of their spectroscopic data, it was concluded that these complexes have similar structures to that previously established for the adduct of 1 with Ag(TFA) (TFA = OC(O)CF3), [Pt3{µ3-Ag(TFA)}(µ-PPh2)3Ph(PPh3)2] (8). The cationic clusters in 3(BF4) and 4(BF4) react with Ag(TFA) to afford cationic adducts in [Pt3{µ3-Ag(TFA)}(µ2-X)(µ-PPh2)2(PPh3)3]BF4 (9(BF4), X = OH; 10(BF4), X = Cl). The structure of the mixed-metal cluster [Pt3(µ3-AgBF4)(µ2-I)(µ-PPh2)2(PPh3)3]BF4 (11(BF4)), obtained by reaction of the complex 2(I) with AgBF4, was determined by X-ray diffraction.

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.