Reactivity of the bis(pentafluorophenyl)boranes ClB(C6F5)(2) and [HB(C6F5)(2)]n towards late transition metal reagents

摘要

The reactivities of the highly electrophilic boranes C1B(C6F5)(2) (1) and [HB(C6F5)(2)](n) (2) towards a range of organometallic reagents featuring metals from Groups 7-10 have been investigated. Salt elimination chemistry is observed between 1 and the nucleophilic anions [(eta(5)-C5R5)Fe(CO)(2)](-) (R = H or Me) and [Mn(CO)(5)](-), leading to the generation of the novel boryl complexes (eta(5)-C5R5)Fe(CO)(2)B(C6F5)(2) [R = H(3) or Me(4)] and (OC)(5)MnB(C6F5)(2) (5). Such systems are designed to probe the extent to which the strongly sigma-donor boryl ligand can also act as a pi-acceptor; a variety of spectroscopic, structural and computational probes imply that even with such strongly electron withdrawing boryl substituents, the pi component of the metal boron linkage is a relatively minor one. Similar reactivity is observed towards the hydridomanganese anion [(eta(5)-C5H4Me)Mn(CO)(2)H](-), generating a thermally labile product identified spectroscopically as (eta(5)-C5H4Me)Mn(CO)(2)(H)B(C6F5)(2) (6). Boranes 1 and 2 display different patterns of reactivity towards low-valent platinum and rhodium complexes than those demonstrated previously for less electrophilic reagents. Thus, reaction of 1 with (Ph3P)(2)Pt(H2C = CH2) ultimately generates EtB(C6F5)(2) (10) as the major boron-containing product, together with cis-(Ph3P)(2)PtCl2 and trans-(Ph3P)(2)Pt(C6F5)Cl (9). The cationic platinum hydride [(Ph3P)(3)PtH](+) is identified as an intermediate in the reaction pathway. Reaction of 2 with [(Ph3P)(2)Rh(mu-Cl)](2), in toluene on the other hand, appears to proceed via ligand abstraction with both Ph3P.HB(C6F5)(2) (11) and the arene rhodium(I) cation [(Ph3P)(2)Rh(eta(6)-C6H5Me)](+) (14) ultimately being formed.