Insertion Reactions in Ta–H and Ta–Me Bonds in Complexes Containing Tridentate κ³O,S,O-Type Ligands

Abstract

A series of new tantalum complexes containing the κ 3 O,S,O-type alkoxide ligand from 2,2′-thiodiethanol (tdgolH 2 ) have been synthesized and characterized. The complexes [TaCp*Cl 2 {[O(CH 2 ) 2 ] 2 S-κ 3 O,S,O}] (1) and [TaCp*Me 2 {[O(CH 2 ) 2 ] 2 Sκ 3 O,S,O}] (2) were prepared by reaction of 2,2′-thiodiethanol with [TaCp*X 4 ] (X = Cl, Me). The tantalum dihydride complex [TaCp*H 2 {[O(CH 2 ) 2 ] 2 S-κ 3 O,S,O}] (3) and its analogue containing the 2,2′-thiobis(6-tert-octylphenolate) ligand (4) were synthesized by reaction of the respective dichlorides with 2 equiv of NaBHEt 3 . In addition, [TaCp*Me(TfO){[O(CH 2 ) 2 ] 2 S-κ 3 O,S,O}] (5) and [TaCp*(TfO) 2 {[O-(CH 2 ) 2 ] 2 S-κ 3 O,S,O}] (6; TfO = F 3 COSO 2 − ) were synthesized by reaction of 2 with 1 and 2 equiv of triflic acid, respectively. The reactivity of this family of complexes with nucleophiles was also studied and, as a result, three azatantalacyclopropane complexes (7−9) and the carbene [TaCp*{C(Me)N(H)xylyl-κ 1 C}(OH){[O(CH 2 ) 2 ] 2 S-κ 3 O,S,O}] (10) were characterized. The single-crystal structures of 1 and 6 were determined by Xray diffraction methods.

Metal-Mediated and Metal-Catalyzed Reactions of Isocyanides

“…A similar reaction of 106 bearing the tridentate [OSO]-type ligand brings about generation of tantallaziridine species 107 (C 6 D 6 , RT, immediate reaction, 100%; Scheme ) …”

“…The same group synthesized and characterized a series of new cationic aminocarbene tantalum complexes 282a – c , obtained by the insertion of CNXyl into the methyl groups of the related neutral triflate complexes 281 (toluene, 100 °C, 24 h, 55–81%; Scheme ). Complexes 282a , b having a triflate counterion are stable even in air, while complex 282c is stable in apolar solvents such as benzene or toluene but decomposes rapidly when dissolved in CDCl 3 and more slowly when the solvent is CD 3 CN.…”

Synthesis of Organotantalum Alkyne Complexes [{η5:σ-Me2C(C5H4)(C2B10H10)}TaMe(η2-R1C≡CR2)] and Their Reactions with Unsaturated Molecules

“…The short Ta–C α (3) distance in 6 associated with the downfield δ C3 value (292.5 ppm) indicated the alkylidene character of the α-carbon (C3). The Ta–O length of 2.060(3) Å is obviously shorter than the dative Ta ← O bond in III (2.181(2) Å) but is slightly longer than the typical Ta–O σ-bonds, such as 1.936(4) Å in [TaCp*­{ O,S,O -[O­(CH 2 ) 2 ] 2 S}­Cl 2 ] and 1.974(3) Å in [TaCp*F 2 { N,O,O -(OCH 2 ) 2 py}] . The C(5)–O length of 1.332(6) Å) is slightly longer than that of 1.265(3) Å in III .…”

Synthesis of NPN-Coordinated Tantalum Alkyl Complexes and Their Hydrogenolysis: Isolation of a Terminal Tantalum Hydride Incorporating a Doubly Cyclometalated NPN Scaffold

“…Since Wilkinson’s synthesis of [TaCp 2 H 3 ] in 1961, Cp-based tantalum hydrides have attracted considerable attention and have been studied in detail by Bercaw, − Schrock, − Tilley, Mountford, , Fryzuk, , and others . In 1973, Tebbe demonstrated that the phosphine-stabilized pentahydride [TaH 5 (dmpe)] can be prepared, which sparked an enduring interest in Cp-free tantalum hydrides and their reactivities, − especially toward small molecules. − In the following decades, phosphine-, amide-, siloxide-, and aryloxide-stabilized tantalum hydrides, such as [TaCl 2 H 2 (PMe 3 ) 4 ], [{TaCl­(μ-H)­(NCy 2 ) 2 } 2 ] , (Cy = cyclohexyl), [Ta­(OSi t Bu 3 ) 3 H 2 ], and [TaCl­(OAr) 2 H 2 (PMe 3 ) 2 ] , (Ar = 2,6- i Pr 2 C 6 H 3 , 2,6-Ph 2 C 6 H 3 ), have been isolated and studied inter alia by Sattelberger, ,, Gambarotta/Cotton, , Wolczanski, ,− and Rothwell. ,,− The groups of Otero and Kawaguchi have shown that chelating aryloxide ligands are also well-suited for the stabilization of tantalum hydrides. − Coordinatively unsaturated tantalum­(III) species, such as [Ta­(OSi t Bu 3 ) 3 ], [Ta­(XylNCH 2 t Bu) 3 ] (Xyl = 3,5-Me 2 C 6 H 3 ), and [Ta­( Ar nacnac)­(N t Bu)] ( Ar nacnac = ArNC­(Me)­CHC­(Me)­NAr with Ar = 2,6- i Pr 2 C 6 H 3 ), were shown to undergo C–H activations to afford the corresponding cyclometalated tantalum­(V) hydrides. With respect to their reactivity, amidophosphine-coordinated tantalum hydrides , certainly stand out, which is particularly true for Fryzuk’s Si NPN -coordinated tetrahydride [{Ta­( Si NPN )} 2 (μ-H) 4 ] (complex II , Si NPN = (PhP­(CH 2 SiMe 2 NPh) 2 ) 2– ; see Scheme ).…”