Multihydride complexes of rhenium, osmium or iridium containing monodentate ditertiary phosphine ligands: selective hydrogen–deuterium exchanges of the rhenium multihydrides

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Abstract
Treatment of [ReH7(PPh3)2] with Ph2PCH2PPh2(dppm) or Ph2PC(=CH2)PPh2(vdpp) gave [ReH7(PPh3)2(L–L-P)](L–L = the diphosphine), accompanied by much [Re2H8(PPh3)4]. However, treatment of [ReH7{P(C6H11)3}2] with dppm, vdpp, Ph2PCH2CH2PPh2(dppe), or cis-Ph2PCHCHPPh2(dppen) gave good yields of the monodentate diphosphine complexes of type [ReH5{P(C6H11)3}2(L–L-P)] without formation of a dirhenium complex of type [Re2H8{P(C6H11)3}4], or chelating diphosphine complexes. The complexes [ReOCl3(PPri 3)2] and [ReOCl3(PBu2 tMe)2] were prepared and characterised. These were reduced by NaBH4 in the presence of the phase-transfer catalyst N(CH2CH2OCH2CH2OMe)3 to give heptahydrides of type [ReH7(PR3)2]. Treatment of [ReOCl3(AsPh3)2] with But 2P(CH2)5PBut 2 probably gave [{ReOCl3[But 2P(CH2)5PBut 2]}x] which with NaBH4 gave [RexH7x{But 2P(CH2)5PBut 2}x] obtained only in an impure form; x is probably 1 or 2. The complex [IrH5{P(C6H11)3}2] with dppm or dppe gave non-fluxional complexes of the type trans-mer-[IrH3{P(C6H11)3}2(L–L-p)](L–L = monodentate dppm or dppe). Substantially pure [OsH6{P(C6H11)3}2] was prepared by reducing [OsO2Cl2{P(C6H11)3}2] with LiAlH4. This hexahydride, with dppm, gave [OsH4{P(C6H11)3}2(dppm-P)] accompanied by [OsH4{P(C6H11)3}(dppm-PP)] as the minor product. Highly selective C–H/C-D exchange was shown to occur between C6D6 and some of the less sterically hindered sites of the co-ordinated diphosphines when compounds of type [ReH5{P(C6H11)3}2(L–L)] were heated in C6D6e.g. with L–L = dppm the product was [ReH5{P(C6H11)3}2{(C6H2D3)2PCH2P(C6H2D3)2}] in which the meta- and para-hydrogens were replaced by deuterium but the ortho-hydrogens were not replaced to a significant extent. Some of the cyclohexyl hydrogens were replaced by deuterium but the CH2 and ReH5 hydrogens were shown to have undergone little exchange with deuterium. Similar results were obtained when [ReH5{P(C6H11)3}2(vdpp-P)] was heated in C6D6 solution. Proton and 31P n.m.r. data are given.