σ-Borane Coordinated to Nickel(0) and Some Related Nickel(II) Trihydride Complexes

Abstract

The reactions of the complexes [(dcype)NiH]2, 1, [(dippe)NiH]2, 2, and [(dtbpe)NiH]2, 3, with a mixture of BEt3 and Super-Hydride (LiHBEt3) afforded sigma-borane nickel(0) compounds of the type [(dcype)Ni(sigma-HBEt2)], 4, [(dippe)Ni(sigma-HBEt2)], 5, [(dtbpe)Ni(sigma-HBEt2)], 6, respectively, with the concomitant formation in each case of [(dcype)2Ni2)(H)3][BEt4], 7, [(dippe)2Ni2(H)3][BEt4], 8 and [(dtbpe)2Ni2(H)3][BEt4], 9, respectively. X-ray crystal structures are reported for 4 and 8. The reaction of BEt3 and LiHBEt3 was also reviewed in detail.

Tert-butylborane: A bis (σ-B–H) ligand in ruthenium hydride chemistry

“…Only three examples involving Mn or Ni and a very limited number of dialkylboranes R 2 BH (R = Cy, Me, Et) have been reported so far [28,29]. The use of monosubstituted boranes (RBH 2 ) as a ligand is even more limited and restricted to mesitylborane ligated in a bis-r coordination mode to a ruthenium center [23][24][25].…”

Experimental and Computational Studies of the Copper Borate Complexes [(NHC)Cu(HBEt3)] and [(NHC)Cu(HB(C6F5)3)]

“…[3d,9] However,w hereas [(6/7Dipp)Cu(m-H)] 2 prove stable for days at 298 K, 2 was stable only below 209 K. Above this temperature,t he 1 HNMR resonances began to broaden and at 255 Ks ignals for 3 were present. [11] TheX -ray structure of 5 ( Figure 1) showed the presence of at wo-coordinate Cu center attached to the carbene and amonodentate {HBEt 3 }moiety.T he hydrogen atom on B(1) was located and refined without restraint, yielding C 6Mes -Cu-Ha nd Cu-H-B angles of 162.4 (13) and 110.2(18)8 8,r espectively,and B-H and Cu-H distances of 1.22(3) and 1.56(3) , respectively.T he latter is comparable to the shortest Cu-H distance in II, [3b] but much shorter than either of the Cu-H bond lengths in III (1.679(2) ,1 .717 (18) ). [3b] Unsurprisingly,e xamples of isolable triethyl-borohydride complexes are rare,b eing confined to very electropositive metals.…”

The σ‐CAM Mechanism: σ Complexes as the Basis of σ‐Bond Metathesis at Late‐Transition‐Metal Centers

“…A recent structure shows an h 2 -HBEt 2 group coordinated to a {Ni(dcpe)} fragment (dcpe = bis(dicyclohexylphosphanyl)ethane) with a BÀH bond length of 1.23 (5) . [37] The complex [RuH(m-H 2 Bpin)(h 2 -HBpin)-(PCy 3 ) 2 ] reported by Sabo-Etienne et al is a unique example allowing a direct comparison between dihydroborate and sborane coordination ( Figure 3). [38] The s-BÀH bond length (1.35 (3) ) is shorter than the BÀH bonds of the dihydroborate ligand (1.58 (3) and 1.47(3) ).…”