Cleavage of Metal−Carbon Bonds in Hydride-Bridged Platinum and Palladium A-Frame Complexes

Abstract

The hydride-bridged A-frame complexes [RPt(μ-H)(μ-dppm)2PtR‘]PF6 and [RPt(μ-H)(μ-dppm)2PdR‘]PF6 react with HCl (generated by reaction of acetyl chloride with water) in acetone-d 6 solution by cleavage of one of the metal−carbon bonds. In the diplatinum systems the relative rates of Pt−C bond cleavage decrease in the order Me > Et > Ph, resulting in a single product in each case. For the heterometallic complexes reaction is faster at palladium, but mixtures of [RPt(μ-H)(μ-dppm)2PdCl]PF6 and [ClPt(μ-H)(μ-dppm)2PdR‘]PF6 result in several instances. Further reaction of these with HCl and/or CCl4 generates the chloride-bridged species [RPt(μ-Cl)(μ-dppm)2PdCl]PF6, formed, in some cases, by migration of the organic group from palladium to platinum. These complexes have been prepared also by reaction of [PtR(dppm-PP)(dppm-P)]PF6 with [PdCl2(cod)]. The [RPt(μ-Cl)(μ-dppm)2PdCl]PF6 complexes are fluxional at 298 K, although the motion may be arrested slightly below ambient temperature. A mechanism involving reversible bridge opening is proposed to account for the fluxional behavior.

Synthesis, Structure, and Electronic Properties of Monomeric and Dimeric Trispyrazolylborate Platinum(II) Hydride Complexes

“…The second large group of complexes contains mixed bridging ligands consisting of a hydride and a carbon, 11,24 sulfur, 25 phosphido, [26][27][28][29] or phosphine bridging ligand. [30][31][32][33][34][35] "Aframe" complexes are the principal subgroup in this set (E in Figure 1). [31][32][33][34][35] Platinum(I), 30-electron species of the general formula [PtHP 2 ] 2 (F in Figure 1) constitute a third group of complexes, [36][37][38][39] although hydride bridges in the ground state structure are only observed with electron-poor phosphines as supporting ligands.…”

“…[30][31][32][33][34][35] "Aframe" complexes are the principal subgroup in this set (E in Figure 1). [31][32][33][34][35] Platinum(I), 30-electron species of the general formula [PtHP 2 ] 2 (F in Figure 1) constitute a third group of complexes, [36][37][38][39] although hydride bridges in the ground state structure are only observed with electron-poor phosphines as supporting ligands. 39 Note that phosphines are the prevalent supporting ligands in these hydride-bridged dinuclear species.…”

Unsymmetrical complexes containing the linear tetraphosphine ligand DPPEPM

“…The usually observed trans arrangement of phosphine units leads to good complex stability [7][8][9][10][11][12][13]. We have been able to prepare a series of thermally stable hydridopalladium (II) derivatives bridged by dppm ligands [14][15][16][17][18], for example, whereas palladium (II) hydrides are generally observed only as unstable reaction intermediates. Although a number of well-defined reactions have been observed, the drawback to this high complex stability is that dppm-bridged species rarely exhibit catalytic activity.…”

“…Thus, the free P atom(s) in 1 or 2, or in 6-8, may be used to generate heterobimetallic species, whereas the two pairs of free P atoms in 3 or 4 allow formation of trimetallic complexes of the type [{PtR 2 (l-DPPEPM)} 2 M][MCl 4 ](15)(16)(17).…”

Synthesis and spectroscopy of binuclear phosphine bridged palladium hydrides: Pd2HX3[dppm]2 (X=Br, I; dppm=bis[diphenylphosphino]methane)

“…The room temperature 31 P-NMR spectra of the symmetrical dipalladium(II) cations [Pd 2 R 2 (m-Cl)dppm 2 ' ][PF 6 ( ] (R 0/CH 3 , Ph) and [Pd 2 R 2 (m-H)dppm 2 ' ][PF 6 ( ] (R0/ CH 3 , Ph) are also singlets while the 31 P spectra of unsymmetrical compounds [Pt 2 (CH 3 6 ( ] [23]. The difficulty with structures A and B is the low molar conductivity for 1b and our inability to exchange one of the halide ligands for PF 6 ( .…”