111026-21-2Relevant articles and documents
Synthesis and reactivity of Pd2Mn, MPdFe, MPdMn2, and MPdFe2 clusters (M = Pd, Pt) stabilized by Ph2PCH2PPh2 (dppm) ligands. Crystal structure of [Pd2Mn2(μ3-CO)(μ-CO)(CO) 7(μ-dppm)2]
Braunstein, Pierre,De Bellefon, Claude De Méric,Ries, Michel,Fischer, Jean
, p. 332 - 343 (2008/10/08)
Heterotetranuclear dppm-stabilized metalloligated clusters have been prepared by reaction of [Fe(CO)3NO]- or [Mn(CO)5]- with the dinuclear d9-d9 complexes [PdMCl2(μ-dppm)2] (M = Pd, Pt). These clusters, of formula [PdMFe2(CO)5(NO)2(μ-dppm)2] (M = Pd, 1a; M = Pt, 1b) and [PdMMn2(CO)9(μ-dppm)2] (M = Pd, 4a; M = Pt, 4b), are characterized by an almost planar metal core, whose Pd-M, M-Fe, and M-Mn edges are bridged by a dppm ligand. The metalloligand Fe(CO)3NO or Mn(CO)5 is always connected to the triangular core PdMFe or PdMMn, respectively, via a Pd atom. This was established by an X-ray diffraction study on 4a: monoclinic, space group P21/c, with Z = 4, a = 17.561 (7) A?, b = 21.319 (8) A?, c = 19.461 (8) A?, β = 113.50 (2)°, and d(calcd) = 1.44 g/cm3. The structure was solved by using 4473 reflections with I > 3σ(I) and refined to conventional R = 0.059 and Rw = 0.082. The Pd(2)-Mn(1) distance (2.580 (2) A?) is shorter than the Pd(1)-Mn(1) distance (2.698 (2) A?) and the exocyclic, unsupported Pd(1)-Mn(2) distance (2.821 (2) A?). The Pd(1)-Pd(2) distance is 2.681 (1) A?. Whereas the coordination about Mn(2) is octahedral, that about Mn(1) can be viewed as highly distorted octahedral. These clusters result from the formal insertion of a Fe(CO)2NO or Mn(CO)4 fragment into the Pd-P bond of the dinuclear precursor. This accounts for the complete regioselective formation of the platinum-containing clusters in which the less labile Pt-P bonds have been retained. The chemistry reported here for the dinuclear MPdP4 and for the MPdFe2P4 or MPdMn2P4 systems takes place within their plane, in contrast to the chemistry leading to A-frame structures. Furthermore, the exocyclic Pd-Fe or Pd-Mn bond of 1 or 4, respectively, is very labile and may be broken sometimes reversibly in dissociating solvents or by other nucleophiles, e.g., halides. Whereas clusters 1 do not react with CO, [PdMFeI(CO)2(NO)(μ-dppm)2] affords cationic clusters in the presence of Tl[PF6], which are characterized by a Pd-bound terminal CO. An effect of platinum that renders its neighboring palladium center more electron-rich is noted and influences the reactivity of the clusters. The Mn-containing clusters are generally more labile than their Fe analogues, and 4b slowly rearranges in solution with formation of the binuclear cation [(OC)4Mn(μ-dppm)Pt(dppm)]+. All complexes were characterized by elemental analyses and IR, 1H NMR, and 31P{1H} NMR spectroscopies. The latter is particularly informative because of the inequivalence of the four phosphorus atoms, and comparisons are made between related systems.
