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

Abstract

The reactivities of the highly electrophilic boranes ClB(C(6)F(5))(2) (1) and [HB(C(6)F(5))(2)](n) (2) towards a range of organometallic reagents featuring metals from Groups 7-10 have been investigated. Salt elimination chemistry is observed 1 between and the nucleophilic anions eta(5)-C(5)R(5))Fe(CO)(2)](-)(R = H or Me) and [Mn(CO)(5)](-), leading to the generation of the novel boryl complexes (eta(5)-C(5)R(5))Fe(CO)(2)B(C(6)F(5))(2)[R = H (3) or Me (4)] and (OC)(5)MnB(C(6)F(5))(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)-C(5)H(4)Me)Mn(CO)(2)H](-), generating a thermally labile product identified spectroscopically as (eta(5)-C(5)H(4)Me)Mn(CO)(2)(H)B(C(6)F(5))(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 (Ph(3)P)(2)Pt(H(2)C=CH(2)) ultimately generates EtB(C(6)F(5))(2) (10) as the major boron-containing product, together with cis-(Ph(3)P)(2)PtCl(2) and trans-(Ph(3)P)(2)Pt(C(6)F(5))Cl (9). The cationic platinum hydride [(Ph(3)P)(3)PtH](+) is identified as an intermediate in the reaction pathway. Reaction of with [(Ph(3)P)(2)Rh(mu-Cl)](2), in toluene on the other hand, appears to proceed via ligand abstraction with both Ph(3)P.HB(C(6)F(5))(2) (11) and the arene rhodium(I) cation [(Ph(3)P)(2)Rh(eta(6)-C(6)H(5)Me)](+) (14) ultimately being formed.

cis-Dichloro(di-tert-butylphosphine-κP)(triphenylphosphine-κP)platinum(II) tetrahydrofuran hemisolvate

“…3indicates only moderate steric repulsion of PPh 3 and P t Bu 2 H groups. It is slightly smaller than the value of 98.73 reported for [cis-(Ph 3 P) 2 PtCl 2 ]Á3CHCl 3 (Al-Fawaz et al, 2004).…”

Development of silica-supported frustrated Lewis pairs: highly active transition metal-free catalysts for the Z-selective reduction of alkynes

“…76 The more informative 11 B spectrum of 3a displays a single signal at -24 ppm, previously attributed in homogeneous studies to the tetrahedral boron from [PPh 3 •HB((C 6 F 5 )] adduct (figure S6). 75 The 31 P NMR signal has shifted from -6.3 ppm in 2 to 10.1 ppm in 3a. The 11 B-31 P correlation spectrum in Figure 3 was acquired using the D-HMQC pulse sequence, which correlates nuclei through their dipolar coupling.…”

“…The intensities and chemical shifts of these three signals are characteristic of the ortho, para and meta fluorine atoms, respectively, on the coordinated HB(C 6 F 5 ) 2 with triphenylphosphine in agreement with literature data. 75 The solid state 19 F NMR spectrum of 3b ( Figure S5b) shows three large signals (-134, -160, -167 ppm) having the comparable chemical shifts as reported for the molecular adduct [PPh 3 •BArF]. 76 The more informative 11 B spectrum of 3a displays a single signal at -24 ppm, previously attributed in homogeneous studies to the tetrahedral boron from [PPh 3 •HB((C 6 F 5 )] adduct (figure S6).…”

Recent chemistry of the η5-cyclopentadienyl dicarbonyl iron anion

“…investigated -back bonding of FpB(C 6 F 5 ) 2 . Although the role of -back bonding in the Fe-B linkage was expected to be strong due to the strong withdrawing effect of the perfluorobenzenes, the role of -back bonding was found [208] to be minor.…”