Cluster core geometrical variation in heterometallic boride clusters containing RhRu₄skeletons: crystal structures of [RhRu₄H₂(η⁵-C₅Me₅)(µ-Cl)(CO)₁₂B] and [RhRu₄H(nbd)(CO)₁₂B(AuPPh₃)](nbd = norbornadiene)

Abstract

The reaction of the butterfly anion [Ru,H(CO),,BH] -with [{Rh(q5-C,Me5)CI,},] gave the novel boroncontaining cluster [RhRu,H,(q 5-C,Me,)(p-CI)(CO), ,B] which has been characterised spectroscopically and by X-ray crystallography. Consistent with the 78 valence-electron (v.e.) count, the five metal atoms adopt an open skeletal structure which can be described as an 'envelope' (or an edge-bridged square) geometry. In contrast, when [Ru,H(CO),,BH] -reacted with [(Rh(nbd)CI},] (nbd = norbornadiene) and [Au(PR,)Cl] (R = Ph, C6H1 or 2-MeC6H,), boride clusters containing both RhRu,B and Rh,Ru,B skeletons were obtained. The presence of the gold(1) phosphine is necessary to trap the RhRu,B-containing product. The Rh,Ru,B clusters possess octahedral frameworks and are related to the previously reported [Rh,Ru,(CO), ,B(AuPR,)] compounds. However, the incorporation of only one rhodium fragment leads to the clusters [RhRu,H(nbd)-(CO),,B(AuPR,)], and a square-based pyramidal RhRu, framework (consistent with a 74 v.e. count) has been confirmed by the results of a single-crystal X-ray diffraction study of [RhRu,H(nbd)(CO), ,B(AuPPh,)].

Gold–Heterometal Interactions and Bonds

“…Two isomers are present in the crystal of (Et 3 P)AuRu 5 (m 5 -C)(NO) (CO) 13 244; both contain a square pyramidal Ru 5 arrangement and differ in the bonding mode of the Au(PEt 3 ) group, that is, m 3 -bonded to a Ru 3 face [Au-Ru 2.783 (2)-3.033(2) Å] in 244a and spanning a Ru-Ru bond between apical and basal atoms [Au-Ru 2.748(2)/2.792(2) Å] in 244b [350]. A similar square pyramidal Ru 5 or Ru 4 Rh core was also found in related m 5 -B derivatives [351,352], but in these cases the Au (PPh 3 ) moiety is m 3 -bridged to the boron and the metal atoms of a Ru-Ru or Ru-Rh bond of the basal plane.…”