4-MEMBERED CHELATE RINGS IN COMPLEXES WITH 2.2-BIS(DIPHENYLPHOSPHINO)PROPANE - CRYSTAL AND MOLECULAR-STRUCTURES OF TRANS-[RUCL2(ME(2)C(PPH(2))(2))(2)], [RUCL(ME(2)C(PPH(2))(2))(ETA-C5H5)] AND H5)RU(MU-CO)(2)(MU-ME(2)C(PPH(2))(2))RHCL2](RH-RU)

The compound Me(2)C(PPh(2))(2) (2,2-dppp) reacted with 0.5 equivalent of [Rh2Cl2(CO)(4)] to afford monomeric [RhCl(CO)(2.2-dppp-P,P')] 1. Me tathesis with LiBr afforded [RhBr(CO)(2.2-dppp-P,P')] 2. With 0.25 equ ivalent of [Rh2Cl2(CO)(4)] the rigid, square-planar [Rh(2,2-dppm)(2)]C l 3 was formed. These results are in sharp contrast to the chemistry s een with H2C(PPh(2))(2) and H(Me)C(PPh(2))(2). With 0.5 equivalent of [RuCl2(PPh(3))(3)], 2,2-dppp reacted to give brown-orange trans-[RuCl2 (2,2-dppp)(2)] 4a. In solution this is in equilibrium with a green fiv e-co-ordinate species [RuCl(2,2-dppp)(2)]Cl 4b, the first such complex to be observed with a four-membered chelating diphosphine. With [RuCl (PPh(3))(2)(eta-C5H5)], 2,2-dppp reacted to form [RuCl(2,2-dppp)(eta-C 5H5)] 5. Although its rhodium(I) chemistry suggests that 2,2-dppp favo urs chelation rather than bridging modes of co-ordination, when 5 was treated with 0.5 equivalent of [Rh2Cl2(CO)(4)] it readily formed [(eta -C5H5)Ru(mu-Co)(2)(mu-2,2-dppp)RhCl2](Rh-Ru) 6. The structures of 4-6 have been determined by X-ray diffraction.