Stabilization of Classical [B2H5]−: Structure and Bonding of [(CpTa)2(B2H5)(μ‐H)L2] (Cp=η5‐C5Me5; L=SCH2S)

• Published in: Angewandte Chemie International Edition Vol. 58; no. 49; pp. 17684 - 17689
• Main Authors: Saha, Koushik, Ghorai, Sagar, Kar, Sourav, Saha, Suvam, Halder, Rajarshi, Raghavendra, Beesam, Jemmis, Eluvathingal D., Ghosh, Sundargopal
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 02.12.2019
• Edition: International ed. in English
• Subjects: Adducts; CS2 activation; Diborane; dithiolates; metal carbonyls; Stability analysis; Tantalum; diborane; tantalum; metal carbonyls; CS2 activation; dithiolates
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201911480

The room‐temperature reaction of [Cp*TaCl4] with LiBH4⋅THF followed by addition of S2CPPh3 results in pentahydridodiborate species [(Cp*Ta)2(μ,η2:η2‐B2H5)(μ‐H)(κ2,μ‐S2CH2)2] (1), a classical [B2H5]− ion stabilized by the binuclear tantalum template. Theoretical studies and bonding analysis established that the unusual stability of [B2H5]− in 1 is mainly due to the stabilization of sp2‐B center by electron donation from tantalum. Reactions to replace the hydrogens attached to the diborane moiety in 1 with a 2 e {M(CO)4} fragment (M=Mo or W) resulted in simple adducts, [{(Cp*Ta)(CH2S2)}2(B2H5)(H){M(CO)3}] (6: M=Mo and 7: M=W), that retained the diborane(5) unit. Isolation of a classical diborane(5) complex of tantalum was achieved by the room‐temperature reaction of [Cp*TaCl4] with LiBH4⋅THF followed by addition of S2CPPh3. Reactivity with metal carbonyls was also explored.