Synthesis, Structures and Chemistry of the Metallaboranes of Group 4–9 with M2B5 Core Having a Cross Cluster M–M Bond

Abstract

In an attempt to expand the library of M2B5 bicapped trigonal-bipyramidal clusters with different transition metals, we explored the chemistry of [Cp*WCl4] with metal carbonyls that enabled us to isolate a series of mixed-metal tungstaboranes with an M2{B4M’} {M = W; M’ = Cr(CO)4, Mo(CO)4, W(CO)4} core. The reaction of in situ generated intermediate, obtained from the low temperature reaction of [Cp*WCl4] with an excess of [LiBH4·thf], followed by thermolysis with [M(CO)5·thf] (M = Cr, Mo and W) led to the isolation of the tungstaboranes [(Cp*W)2B4H8M(CO)4], 1–3 (1: M = Cr; 2: M = Mo; 3: M = W). In an attempt to replace one of the BH—vertices in M2B5 with other group metal carbonyls, we performed the reaction with [Fe2(CO)9] that led to the isolation of [(Cp*W)2B4H8Fe(CO)3], 4, where Fe(CO)3 replaces a {BH} core unit instead of the {BH} capped vertex. Further, the reaction of [Cp*MoCl4] and [Cr(CO)5·thf] yielded the mixed-metal molybdaborane cluster [(Cp*Mo)2B4H8Cr(CO)4], 5, thereby completing the series with the missing chromium analogue. With 56 cluster valence electrons (cve), all the compounds obey the cluster electron counting rules. Compounds 1–5 are analogues to the parent [(Cp*M)2B5H9] (M= Mo and W) that seem to have generated by the replacement of one {BH} vertex from [(Cp*W)2B5H9] or [(Cp*Mo)2B5H9] (in case of 5). All of the compounds have been characterized by various spectroscopic analyses and single crystal X-ray diffraction studies.

Heterometallic Triply‐BridgingBis‐Borylene Complexes

“…Using TLC plates the residue was chromatographed. Elution with a CH2Cl2/hexane (20:80 v/v) afforded orange 1 (0.010 g, 11 %) and yellow 2 (0.020 g, 21 %) along with known [(Cp*W)2B4H8Fe(CO)3] 34 (0.010 g, 12 %) and [(Cp*W)2B5H9] 35 (0.020 g, 27 %).…”

Polyhedral [M2B5] Metallaborane Clusters and Derivatives: An Overview of Their Structural Features and Chemical Bonding

“…A series of Mo and W derivative compounds with different metal carbonyl fragments were obtained previously from the reaction of the intermediate formed from the reaction of [Cp*MCl 4 ] (M = Mo or W) and LiBH 4 , with the corresponding metal carbonyls M(CO) 5 ·thf (M = Cr, Mo, W). The reaction of the Mo metallaborane intermediate yielded [(Cp*Mo) 2 B 4 H 6 W(CO) 5 ], 12 , [(Cp*Mo) 2 B 4 H 8 W(CO) 4 ], 13 , and [(Cp*Mo) 2 B 4 H 8 Cr(CO) 4 ], 14 [ 72 , 73 ]. In the case of W system, the similar reaction yielded [(Cp*W) 2 B 4 H 8 M’(CO) 4 ], 15–17 ( 15 : M’ = Cr; 16 : M’ = Mo; 17 : M’ = W) [ 73 ].…”

“…The reaction of the Mo metallaborane intermediate yielded [(Cp*Mo) 2 B 4 H 6 W(CO) 5 ], 12 , [(Cp*Mo) 2 B 4 H 8 W(CO) 4 ], 13 , and [(Cp*Mo) 2 B 4 H 8 Cr(CO) 4 ], 14 [ 72 , 73 ]. In the case of W system, the similar reaction yielded [(Cp*W) 2 B 4 H 8 M’(CO) 4 ], 15–17 ( 15 : M’ = Cr; 16 : M’ = Mo; 17 : M’ = W) [ 73 ]. Finally, reaction of the W intermediate with Fe 2 (CO) 9 generated [(Cp*W) 2 B 4 H 8 Fe(CO) 3 ], 18 [ 73 ], while the reaction of the isolated intermediate [Cp*WH 3 (B 4 H 8 )] with Ru 3 (CO) 12 resulted in the analogous cluster, 19 ( Scheme 2 ) [ 74 ].…”

“…Due to their unique structure, thorough theoretical studies were performed by us and others in order to get some insight into their electronic structure and chemical bonding [ 66 , 67 , 68 , 69 , 70 ]. Later, many heterometallic [ 63 , 71 , 72 , 73 , 74 ] and chalcogenated derivatives of oblatonido-M 2 B 5 [ 75 , 76 , 77 , 78 ] were reported in the literature, which are isostructural as well as isoelectronic. In all these derivatives, one vertex in the parent cluster is replaced by an isolobal metal fragment or a chalcogen atom.…”

Triple-Decker Sandwich Complexes of Tungsten with Planar and Puckered Middle Decks

“…The W-W bond length of 2.790 Å is slightly shorter in comparison with other ditungstaboranes indicating a strong cross cluster bonding. [21][22] The core geometry of 1 is analogues to that of [(Cp*Re)2{μ-η 6 :η 6 -B4H4Co2(CO)5}] ed by Fehlner. 17 The presence of two bridging hydrogens in 1 was identified by 1 H NMR.…”