Mixed-metal rhenium-platinum cluster compounds. Synthesis and characterization of three isomers of the triangular cluster complex [Re2Pt(.mu.-H)2(CO)8(PPh3)2]

Abstract

The reaction between [Re,(~-H),(CO),] and [Pt(PPh3),(C,H4)] at 273 K results in the insertion of the [Pt(PPh3),] fragment into a Re(pH)Re bond, giving the triangular cluster [RezPt(p-H)z(CO),(PPh3)2], characterized spectroscopically. On increasing the temperature, an irreversible transformation occurs, due to the exchange of one phosphine and one carbonyl between platinum and rhenium. Two other isomers are formed in this way, characterized by 'H and 31P NMR, which differ in the location of the phosphine bound to rhenium. They equilibrate slowly on the NMR time scale, and variable-temperature experiments allowed the estimation of the thermodynamic parameters of this isomerization: AHe = -1.72 f 0.04 kcal mol-', ASe = -4.56 f 0.14 cal mol-' K-l. NMR 2D reverse correlation experiments were performed to detect lg5Pt chemical shifts of the three isomers and to measure the passive couplings with 31P not observable in the 1D spectra. The relative signs of these couplings are discussed. One of the isomers has been investigated by X-ray single-crystal analysis. It gives monoclinic crystals, space group B l / c (No. 14), with a = 14.044 (3), b = 19.343 (5), c = 16.391 (3) A, 0 = 93.69 ( 2 ) O , 2 = 4. The refinements, based on 5306significant observations, gave a final R value of 0.031. It contains a PtRez triangle with the Re-Re edge and one of the Pt-Re edges supposed to be bridged by hydride ligands. The Pt atom bears one PPh3 and one CO ligand and exhibits approximately a square-planar coordination. The two Re atoms show octahedral environments, one bearing four CO and the second one three CO and a PPh3 ligand, coordinated in the axial direction with respect to the cluster plane. The hydrogen-bridged Re-Re bond is 3.203 (1) A long; the two Pt-Re bond lengths are 2.906 (1) and 2.788 (1) A, for the hydrogen-bridged edge and for the unbridged one, respectively.

Stepwise addition of PtPPh3fragments on [Re2(CO)10]. X-Ray crystal structures of the complexes [Re2Ptn(µ-CO)2n(CO)10 – 2n(PPh3)n](n= 2, 3), the first examples of tetra-and penta-nuclear rhenium–platinum mixed-metal clusters

“…2 We have now found that compound 1 is able to react in mild conditions with the ethane-like molecule [Re2(CO)ro], 3, through a completely different pathway, leading to the addition of up to three PtPPh3 fragments on [Rez(CO)lo]. The reaction, at room temperature, went to completion by bubbling N2 (to remove C2H4) through a solution of 3 and an excess of 1 (ca.…”

A Highly Unsaturated Platinum–Rhenium Cluster Complex Activates Hydrogen Reversibly

“…It is related to a number of similar compounds that have been reported. [4] Compound 4 contains four metal atoms: two of platinum and two of rhenium. The molecular structure of 4 was established crystallographically.…”

“…It was found that 4 adds one equivalent of H 2 (1 atm/ 25 8C) to yield the new tetrahydrido compound [Pt 2 Re 2 (CO) 7 -(PtBu 3 ) 2 (m-H) 4 ] (5) in 71 % yield. Compound 5 was also characterized crystallographically.…”

Binary Carbonyls, Carbonyls plus Hydrides, Carbonyls plus Phosphines, Cyclic Hydrocarbyls and Main-group Ligands without Acyclic Hydrocarbyls

“…The solid-state structure of (35) has been determined, 129 and in both these isomers one of the PPh 3 groups is ligated to a rhenium atom. This isomerization hence requires an exchange of a CO and phosphine ligand between the rhenium and platinum centres.…”

“…A very interesting form of isomerism is shown by the complex [Mo 2 Fe 2 (n 3 -S) 2 (CO) 8 CP 2 ] (CP = Cp or Cp 1 ) (128) and (129). 484 " 7 The two isomers differ in the metal core geometry in that (128) has a butterfly skeleton, while (129) has a planar skeleton.…”