Reaction Scope and Mechanism of Sterically Induced Ruthenium-Mediated Intramolecular Coupling ofo-Carboranyl with Cyclopentadienyl. Synthesis and Structure of Ruthenium Complexes Incorporating Doubly Linked Cyclopentadienyl−Carboranyl Ligands

Abstract

Reactions of [Me(R1)A(C5H3R2)(C2B10H10)]Li2 (A = C, Si; R1 = H, Me; R2 = H, Me) with 1 equiv of RuCl2(PPh3)3 in THF afforded the corresponding doubly linked cyclopentadienyl−carboranyl ruthenium(II) hydride complexes [η 5-Me2C(C5H3)(C2B10H10)]RuH(PPh3)2 (6), [η 5-MeHC(C5H3)(C2B10H10)]RuH(PPh3)2 (7), [η 5-Me2C(5-Me-C5H2)(C2B10H10)]RuH(PPh3)2 (8), [η 5-Me2C(3/4-Me-C5H2)(C2B10H10)]RuH(PPh3)2 (9a/9b), and [η 5-Me2Si(C5H3)(C2B10H10)]RuH(PPh3)2 (10) in 72−85% isolated yields. On the other hand, interaction of [Me2C(C5H4)(C2B10H10)]Li2 with 1 equiv of RuCl2[PPh2(OEt)]3 produced only [η 5:σ-Me2C(C5H4)(C2B10H10)]Ru[PPh2(OEt)]2 (14). An equimolar reaction of [Me2C(C5H4)(C2B10H10)]Li2 with RuCl2(PPh3)3 in the presence of dppe (dppe = 1,2-bis(diphenylphosphino)ethane) generated [η 5:σ-Me2C(C5H4)(C2B10H10)]Ru(dppe) (15). No ruthenium hydride complexes were detected in the latter two cases. Treatment of [η 5-Me2C(C5H3)(C2B10H10)]RuH(PPh3)2 (6) with excess HBF4·OEt2 in toluene gave the neutral ligand Me2C(C5H4)(C2B10H10) (12). This work showed that such intramolecular coupling reactions were driven by steric factors. A possible reaction mechanism was proposed to account for these ruthenium-mediated coupling reactions. All new complexes were fully characterized by multinuclear NMR techniques and elemental analyses. Molecular structures of 6, 7, and 8 were further confirmed by single-crystal X-ray analyses.

Dinitrogen Activation of Cyclopentadienyl-Phosphine–Iron Complexes of Three Different Valences

“…30 Different ligands significantly affect the coordination configuration of the iron center, and thus influence the activation of dinitrogen. Although the simple combination of cyclopentadienyl ligands and phosphine ligands was used in several dinitrogen complexes, [38][39][40][41][42][43][44][45] studies on iron-dinitrogen complexes bearing cyclopentadienylphosphine ligands, for example L in Scheme 1, in which the two commonly used strong coordination moieties of different steric and electronic properties are linked together, are few due to the formation of stable sandwich-type ferrocene structures. [46][47][48] We have previously developed a convenient synthetic method for cyclopentadienyl-phosphine ligands (L).…”

Dicarba-closo-dodecarborane-containing half-sandwich complexes of ruthenium, osmium, rhodium and iridium: biological relevance and synthetic strategies

“…96 In 2006, the same authors published an extension of this work in-which a series of cyclopentadienyl-carboranyl halfsandwich complexes of ruthenium was synthesised following the same strategy. 97 Based on different examples, they showed that the coupling reaction of the Cp ring with the dicarbacloso-dodecarborane derivative requires the absence of a substituent on one of the carbon atoms of the cyclopentadienyl unit. Moreover, the presence of a triphenylphosphine coordinated to the metal atom is essential, which indicates a mechanism based on sterically-induced coupling.…”

Unique chemical properties of metal-carbon bonds in metal-carboranyl and metal-carboryne complexes

“…Treatment of the dilithium salts of [Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )] 2− with [RuCl 2 (COD)] x at room temperature affords the constrained-geometry ruthenium carboranyl complexes [η 5 :σ-Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )]Ru(COD) [48] . On the other hand, interaction between Li 2 [Me 2 C(C 5 H 4 )(C 2 B 10 H 10 )] and RuCl 2 (PPh 3 ) 3 in a 1 : 1 molar ratio at room temperature gives a ruthenium(Ⅱ ) hydride complex [η 5 -C 5 H 3 {Me 2 C(C 2 B 10 H 10 )}]RuH(PPh 3 ) 2 (27) bearing a new ligand formed by a C cage -C ring coupling (Scheme 11) [49,57] . This result is unexpected and very different from literature work [55,56] .…”