Synthesis and Crystal Structure of [Ru2(CO)4(μ-H)(μ-NO)(μ-PtBu2)(μ-PPh2CH2PPh2)]BF4

The reaction of the coordinatively unsaturated complex [Ru-2(CO)(4)(mu-H)(mu-PtBu2)(mu-dppm)] (1, dppm = Ph2PCH2PPh2)] with the nitrosonium ion was revisited. Even by variation of the reaction conditions, the reaction afforded in each case not the sole addition product [Ru-2(CO)(4)(mu-NO)(mu-H)(mu-PtBu2)(mu-dppm)](+) (2) as reported by us in an earlier paper. Instead always a mixture of three compounds containing the complexes [Ru-2(CO)(4)(mu-H)(2)(mu-PtBu2)(mu-dppm)](+) (3), [Ru-2(CO)(4)(mu-NO)(mu-PtBu2)(mu-dppm)] (4), beside the originally described complex 2 was obtained. A new synthetic procedure affording compound 4 as the sole product by reaction of 1 with the nitrosylating reagent diazald (N-methyl-N-nitroso-p-toluenesulfonamide) is described. It was found that complex 2 can act as an acid strong enough to protonate the starting complex 1. Thus, the formation of the mixture of components in the title reaction could be explained. A mixing experiment of equimolar amounts of 1 and 2 showed unambiguously the formation of complexes 3 and 4. A clean preparation of complex 2 as the sole product in form of its tetrafluoridoborate salt is only possible by reaction of 4 with tetrafluoridoboric acid in diethyl ether solution. The X-ray crystal structure of [2]BF4 is reported confirming the molecular structure of the complex 2. Using the originally described preparation route for 2 afforded in each attempt of crystallization the complexes 2 and 3 as 1:1 mixture in the solid.