Metal-Rich Metallaboranes: Synthesis, Structure, and Bonding of Heteronuclear Trimetallic Clusters containing (μ3-BH) Ligand

Building upon our earlier results on the chemistry of nido-1,2-[(Cp*RuH)(2)B3H7] (Cp*=ɳ(5)-C5Me5) (nido-1) with different transition metal carbonyls, we continued to investigate the reactivity with group 7 metal carbonyls under photolytic condition. Photolysis of nido-1 with [Mn-2(CO)(10)] led to the isolation of a trimetallic [(Cp*Ru)(2){Mn(CO)(3)}(& mu;-H)(& mu;-CO)(3)(& mu;(3)-BH)] (2) cluster with a triply bridging borylene moiety. Cluster 2 is a rare example of a tetrahedral cluster having hydrido(hydroborylene) moiety. In an attempt to synthesize the Re analogue of 2, a similar reaction was carried out with [Re-2(CO)(10)] that yielded the trimetallic [(Cp*Ru)(2){Re(CO)(3)}(& mu;-H)(& mu;-CO)(3)(& mu;(3)-BH)] (3) cluster having a triply bridging borylene unit. Along with 3, a trimetallic square pyramid cluster [(Cp*Ru)(2){Re(CO)(3)}(& mu;-H)(2)(& mu;-CO)(& mu;(3),ɳ(2)-B2H5)] (4), and heterotrimetallic hydride clusters [{Cp*Ru(CO)(2)}-{Re(CO)(4)}(2)(& mu;-H)] (5) and [{Cp*Ru(CO)}{Re(CO)(4)}(2)(& mu;-H)(3)] (6) were isolated. Cluster 4 is a unique example of a M2M & PRIME;B-2 cluster having diboron capped Ru2Re-triangle. The hydride clusters 5 and 6 have triangular RuRe2 frameworks with one and three & mu;-Hs respectively. All the clusters have been characterized by using mass spectrometry, H-1, B-11{H-1}, C-13{H-1} NMR and IR spectroscopies analyses and the structures of clusters 2-6 have been unambiguously established by XRD analyses. Furthermore, to understand the electronic, structural, and bonding features of the synthesized metal-rich clusters, DFT calculations have been performed.