Synthesis, Structure, and Stability of Adducts between Phosphide and Amide Anions and the Lewis Acids Borane, Tris(pentafluorophenyl)borane, and Tris(pentafluorophenyl)alane

Abstract

The phosphinoborane adduct H(3)P x B(C(6)F(5))(3) can be deprotonated using LiN(SiMe(3))(2) to give the phosphidoborate salt Li[H(2)PB(C(6)F(5))(3)], which was converted to the phosphidodiborates Li[H(2)P{B(C(6)F(5))(3)}(2)] and Li[H(2)P{B(C(6)F(5))(3)}{BH(3)}] by treatment with an equivalent of B(C(6)F(5))(3) or Me(2)S.BH(3), respectively. A series of anions of the form [RR'P{M(C(6)F(5))(3)}{BH(3)}](-), where R = R' = Ph or R= (t)Bu, R' = H, and M = B or Al, were prepared (through treatment of salts Li[RR'P(BH(3))] with the corresponding Lewis acid) and characterized using multinuclear NMR, elemental analysis and X-ray crystallography. The solid state structures of [Li(Et(2)O)(x)][Ph(2)P{M(C(6)F(5))(3)}{BH(3)}] exhibit eta(2)-bonding of the BH(3) group to the cationic lithium center. The attempted preparation of an analogous series with amide cores of the form [R(2)N{B(C(6)F(5))(3)}{BH(3)}](-) proved unsuccessful; among the competing reaction pathways hydride abstraction occurred preferentially to yield Li[HB(C(6)F(5))(3)] and dimers or higher oligomers with the composition (R(2)NBH(2))(n).

Stable Borane Adducts of Alcoholates and Carboxylates

“…On the other hand, complexes of the conjugate base anions, namely carboxylates and phosphinates with B(C 6 F 5 ) 3 are also stable as demonstrated by the isolation and full characterization of the complex anions [ R CO 2 · B(C 6 F 5 ) 3 ] – ( R = H; R = Me), [RCO 2 · 2B(C 6 F 5 ) 3 ] –[20] and [Ph 2 PO 2 · B(C 6 F 5 ) 3 ] – , respectively. This stability compliments a large number of stable adducts between inorganic anions and B(C 6 F 5 ) 3 including 1:1 complexes [ X · B(C 6 F 5 ) 3 ] – ( X = H, OH,, , F, Cl,, PhNH, PhS, CN, SCN, NO 3 , [HSO 3 ,, ) as well as 1:2 complexes [ X · 2 B(C 6 F 5 ) 3 ] – ( X = OH,, NH 2 , PH 2 , CN,, ) and [ X · 2 B(C 6 F 5 ) 3 ] 2– ( X = O, SO 4 ), respectively. In this context, the neutral donor‐acceptor complex (C 6 F 5 ) 3 B · N(H)SO needs to be also mentioned .…”

Synthesis and Structure of Amido‐ and Imido(pentafluorophenyl)borane Zirconocene and Hafnocene Complexes: NH and BH Activation

“…We propose that the hydridoborate salt results from the abstraction of hydride from 3 a or 4 a by B(C 6 F 5 ) 3 (Scheme ). In support of this hypothesis, treatment of 3 a with B(C 6 F 5 ) 3 , in the absence of metallocene, yields Li[HB(C 6 F 5 ) 3 ] 36…”

“…. [36] Surprisingly, given the established similarity between zirconium and hafnium, rather different mechanisms appear to be in operation (Scheme 8). [37] For zirconium, the nucleophilic lithium reagent is presumed to react with the electrophilic metal centre, produced through reversible dissociation of the [MeBA C H T U N G T R E N N U N G (C 6 F 5 ) 3 ] À anion.…”

Phosphido-Borane and Phosphido-Bis(Borane) Complexes of the Alkali Metals, a Comparative Study

“…While these ligands may adopt a wide variety of coordination modes there appears to be a marked preference for the formation of BH 3 ···M contacts in their complexes with hard (9), Na···B(1)···Na′ 91.12 (9). Primed atoms are related by the inversion symmetry operation 1−x, 1−y, 1−z.…”

“…To date, only three such compounds have been structurally characterized, namely, {R 2 P(BH 3 ) 2 }K (18-crown-6) [R = Ph (1), t-Bu (2)] 4b, 7 and {(2,4,6-t-Bu 3 C 6 H 2 )PH(BH 3 ) 2 }-Li(THF) 3 (3); 8 all three compounds crystallize as contact ion pairs in which the alkali metal cations are coordinated by the ether or tetrahydrofuran (THF) co-ligands and by only one of the BH 3 groups of the phosphido-bis(borane) ligand. In addition, Lancaster and co-workers have reported the crystal structure of the mixed phosphido-bis(borane) complex [Ph 2 P-{B(C 6 F 5 ) 3 }(BH 3 )]Li(Et 2 O) 3 (4), 9 while Bertrand and coworkers have reported the crystal structure of the unusual hydride-bridged complex [{(2,4,6-t-Bu 3 C 6 H 2 )P(BH 3 ){(μ-BH 2 ) 2 H}}Li(THF) 2 ] 2 . 8 We recently reported the synthesis and crystal structures of a series of alkali metal phosphido-borane complexes possessing peripheral donor functionalization through the incorporation of a benzyl ether or thioether group in the ligand (5−10, Chart 1).…”