Chemistry and Electrochemistry of the Heterodinuclear Complex ClPd(dppm)₂PtCl:  A M−M‘ Bond Providing Site Selectivity

Abstract

The heterodinuclear d(9)-d(9) title compound 1, whose crystal structure has been solved, reacts with dppm [bis(diphenylphosphino)methane] in the presence of NaBF4 to generate the salt [ClPd(mu-dppm)2Pt(eta(1)-dppm)][BF4] (2a), which contains a Pt-bound dangling dppm ligand. 2a has been characterized by 1H and 31P NMR, Fourier transform Raman [nu(Pd-Pt) = 138 cm(-1)], and UV-vis spectroscopy [lambda(max)(dsigma-dsigma*) = 366 nm]. In a similar manner, [ClPd(mu-dppm)2Pt(eta(1)-dppm=O)][BF4] (2b), ligated with a dangling phosphine oxide, has been prepared by the addition of dppm=O. The molecular structure of 2b has been established by an X-ray diffraction study. 2a reacts with 1 equiv of NaBH4 to form the platinum hydride complex [(eta(1)-dppm)Pd(mu-dppm)2Pt(H)][BF4] (3). Both 2a and 3 react with an excess of NaBH4 to provide the mixed-metal d(10)-d(10) compound [Pd(mu-dppm)3Pt] (4). The photophysical properties of 4 were studied by UV-vis spectroscopy [lambda(max)(dsigma-dsigma*) = 460 nm] and luminescence spectroscopy (lambda(emi) = 724 nm; tau(e) = 12 +/- 1 micros, 77 K). The protonation of 1 and 4 leads to [ClPd(mu-dppm)2(mu-H)PtCl]+ (5) and 3, respectively. Stoichiometric treatment of 1 with cyclohexyl or xylyl isocyanide yields [ClPd(mu-dppm)2Pt(CNC6H11)]Cl (6a) and [ClPd(mu-dppm)2Pt(CN-xylyl)]Cl (6b) ligated by terminal-bound CNR ligands. In contrast, treatment of 1 with the phosphonium salt [C[triple bond]NCH2PPh3]Cl affords the structurally characterized A-frame compound [ClPd(mu-dppm)2(mu-C=NCH2PPh3)PtCl]Cl (6c), spanned by a bridging isocyanide ligand. The electrochemical reduction of 2a at -1.2 V vs SCE, as well as the reduction of 5 in the presence of dppm, leads to a mixture of products 3 and 4. Further reduction of 3 at -1.7 V vs SCE generates 4 quantitatively. The reoxidation at 0 V of 4 in the presence of Cl- ions produces back complex 2a. The whole mechanism of the reduction of 1 has been established.

A‐Frame‐Containing Organometallic Oligomers Constructed From Homo‐ and Heterobimetallic M(μ‐dppm)2M′ (M/M′ = Pd, Pt) Building Blocks

“…This preference for the plati-num site in substitution reactions was noticed previously by us from the reactivity of the heterobimetallic complex 1a towards isocyanides, phosphanes, and hydrides. [10] …”

Mixed-Ligand Organometallic Polymers Containing the “Pd2(dmb)22+” Fragment: Properties of the {Pd2(dmb)2(diphos)2+}n Polymers/Oligomers in Solution and in the Solid State

“…39 In addition, the Raman spectra of PdPt(dppm) 2 Cl 2 and [PdPt(dppm) 2 (η 1 -dppm)Cl]PF 6 have been investigated by this group, placing ν(PdPt) at 154 and 138 cm -1 , respectively. 40 Assuming that the decrease in ν(PdPt) for the replacement of one Cl ligand by a phosphine group (16 cm -1 ) can also apply for a second substitution, then the predicted ν(PdPt) value would be 122 cm -1 (138-16 ) 122). The assignment of the 119 cm -1 peak to ν(Pd 2 ) for 4 appears reasonable.…”

Synthesis of Vinyl Isocyanides and Development of a Convertible Isonitrile

“…Isocyanomethylenetriphenylphosphorane, synthesized in 1985 by Fehlhammer, has remained a laboratory curiosity. Indeed, coordination to transition metal and subsequent [3 + 2] cycloaddition with carbon disulfide is the only reported transformation known to date .…”