Synthesis of palladium clusters with the P-N-P assembling ligands (Ph2P)(2)CH2 (dppm) and (Ph2P)(2)NH (dppa). Crystal structure of [Pd-4(mu-Cl)(2)(mu-dppm)(2) (mu-dppa)(2)](PF6)(2)

Tetrapalladium clusters containing dppa or dppa and dppm bridging ligands w ere prepared by condensation of dinuclear units. Reaction of [Pd2Cl2(mu-dpp a)(2)] with [Cu(PPh3)]PF6 (generated in situ in THF) yielded [Pd-4(mu-Cl)(2 )(mu-dppa)(4)] (PF6)2 (4) in a virtually quantitative yield but [Pd-4(mu-Cl )(2)(mu-dppm)(2)(mu-dppa)(2)] (PF6)(2) (6) was best prepared in CH2Cl2 from [Pd2Cl2(mu-dppm)(2)] and [Pd-2(MeCN)(2)(mu-dppa)(2)](PF6)(2) (2). The stru cture of 6 . 2(CH3)(2)CO . 2H(2)O was determined by X-ray diffraction. It c onsists of a planar, centrosymmetric 10-membered ring structure. The four b ridging diphosphine ligands are of two types: two dppa ligands support the Pd-Pd bonds [2.6055(3) Angstrom], whereas the two dppm ligands bridge betwe en two palladium atoms separated by 3.722(4) Angstrom, which are also bridg ed by a chloride ligand.