Synthesis and crystal structure of the novel dianion [Re(CO)3(η5-7-CB10H11)]2-.: Reactions with platina- and palladaphosphine chlorides

The salts [X](2)[Re(CO)(3)(eta(5)-7-CB10H11)] (X = N(PPh3)(2) (2a), X = NEt3(CH2Ph) (2b)) have been synthesized from the reaction between [Na](3)[nido-7-CB10H11] and [ReBr(THF)(2)(CO)(3)] (THF = tetrahydrofuran) followed by addition of XCl. An X-ray diffraction study revealed that 2b crystallizes in the orthorhombic space group Pna2(1). The anion of 2a could not be oxidized by a host of oxidants with the exception of I-2, which yielded the salt [N(PPh3)(2)]-[ReI(CO)(3)(eta(5)-7-CB10H11)] (3) The neutral bimetallic complexes [RePt(CO)(3)(L)(2)(eta(5)-7-CB10H11)] (L = PPh3 (4a), L = PEt3 (4b), (L)(2) = Ph2P(CH2)(2)PPh2 (4c)) have been prepared by treating 2a in THF with [PtCl2(L)(2)] in the presence of TIPF6. X-ray diffraction revealed that compound 4a crystallizes in the monoclinic space group C2/c. The molecule contains a bridging nido-7-CB10H11 ligand which is eta(5)-coordinated to the Re atom and is bound to the Pt atom by a B-beta-H --> Pt agostic bond. The compound [RePd(CO)(3){Ph2P(CH2)(2)PPh2}(eta(5)-7-CB10H11)] (5a) has been prepared by treating 2a with [PdCl2{Ph2P(CH2)(2)PPh2}] in THF in the presence of TlPF6. X-ray diffraction showed that 5a crystallizes in the orthorhombic space group P2(1)2(1)2(1), and the structure in the solid-state is similar to that of 4a but with a B-beta-H --> Pd agostic bond. In solution, an exchange occurs on the NMR time scale between the B-H bonds in the coordinating CBBBB face which form the B-H --> Pd linkage, thus generating a pseudo plane of symmetry in the molecule. Treatment of CH2Cl2 solutions of 5a with CNR (R = Bu-t, C6H3Me2-2,6) at -78 degrees C yields the complexes [RePd(CO)(2)(CNR){Ph2P(CH2)(2)PPh2}(eta(5)-7-CB10H11)] (R = Bu-t (5b), R = C6H3Me2-2,6 (5c)). The IR and NMR spectra of the new compounds are discussed.