Reductions of M{N(SiMe₃)₂}₃ (M = V, Cr, Fe): Terminal and Bridging Low-Valent First-Row Transition Metal Hydrido Complexes and “Metallo-Transamination”

Abstract

The reaction of the vanadium(III) tris(silylamide) V{N(SiMe 3 ) 2 } 3 with LiAlH 4 in diethyl ether gives the highly unstable mixed-metal polyhydride [V(μ 2 -H) 6 [Al{N(SiMe 3 ) 2 } 2 ] 3 ]-[Li(OEt 2 ) 3 ] (1), which was structurally characterized. Alternatively, performing the same reaction in the presence of 12-crown-4 affords a rare example of a structurally verified vanadium terminal hydride complex, [VH{N(SiMe 3 ) 2 } 3 ][Li(12-crown-4) 2 ] (2). The corresponding deuteride 2D was also prepared using LiAlD 4 . In contrast, no hydride complexes were isolated by reaction of M{N(SiMe 3 ) 2 } 3 (M = Cr, Fe) with LiAlH 4 and 12-crown-4. Instead, these reactions afforded the anionic metal(II) complexes [M{N(SiMe 3 ) 2 } 3 ][Li(12-crown-4) 2 ] (3, M = Cr; 4, M = Fe). The reaction of the iron(III) tris(silylamide) Fe{N(SiMe 3 ) 2 } 3 with lithium aluminum hydride without a crown ether gives the "hydrido inverse crown" complex [Fe(μ 2 -H){N(SiMe 3 ) 2 } 2 (μ 2 -Li)] 2 (5), while treatment of the same trisamide with alane trimethylamine complex gives the iron(II) polyhydride complex Fe(μ 2 -H) 6 [Al{N(SiMe 3 ) 2 } 2 ] 2 [Al{N(SiMe 3 ) 2 }(NMe 3 )] (6). Complexes 2−6 were characterized by X-ray crystallography, as well as by infrared, electronic, and 1 H and 13 C (complex 6) NMR spectroscopies. Complexes 1 and 6 are apparently formed by an unusual "metallo-transamination" process.

Poly(2-Hydroxyethyl methacrylate-co-N,N-dimethylacrylamide)-Coated Quartz Crystal Microbalance Sensor: Membrane Characterization and Proof of Concept

“…For the case of the 3 + charged cations; the Cr(III) (0.69A ionic radius) showed higher Qe than Fe(III) (0.64 A ionic radius). Without being conclusive, there is an apparent relationship between the possible size of the cation and Qe; this could imply that cations with ionic radius approaching to 1A have greater susceptibility to generate interactions with the hydrophilic functional groups present in the polymeric chains of the HEMA/DMAa membranes; apparently, the size of the cation is determinant, as has been argued in previous reports [48][49][50][51].…”

Hydrides, Halides, and Polymers: Some Unexpected Intermediates on the Routes to First-Row Transition Metal M{N(SiMe3)2}n (n = 2, 3) Complexes

“…[Na 2 Mg 2 {N(Pr i ) 2 } 4 (μ-H) 2 •(toluene) 2 ]) originally reported by Mulvey and co-workers. 56 We recently reported that the donor solvent-free iron/lithium inverse crown could be prepared by reaction of Fe{N(SiMe 3 ) 2 } 3 with lithium aluminum hydride, 33 and the isolation of titanium/ sodium 3 further highlights that this structural motif is likely accessible for a variety of metals. The structure of 3 suggests that the reduction of [Ti(μ-Cl){N(SiMe 3 ) 2 } 2 ] 2 (1) with sodium metal may transiently form a divalent "Ti{N-(SiMe 3 ) 2 } 2 " species that then subsequently reacts with ligand CH moieties to form the hydride complex 3.…”

“…A coordination chemistry was initiated for the titanium and vanadium tris­(silylamide) complexes (previously thought not possible due to steric crowding) to give M­{N­(SiMe 3 ) 2 } 3 L 2 (L = a nitrile or isocyanide ligand) complexes . Additionally, the isolation of a new vanadium­(V) oxy silylamide complex, e.g., V­(=O)­{N­(SiMe 3 ) 2 } 3 , that was absent from the literature despite several attempts to isolate it, and the synthesis of several unusual metal hydride complexes that are available by reduction of M­{N­(SiMe 3 ) 2 } 3 complexes were described …”

“…31 Additionally, the isolation of a new vanadium(V) oxy silylamide complex, e.g., V(=O){N-(SiMe 3 ) 2 } 3 , that was absent from the literature despite several attempts to isolate it, 32 and the synthesis of several unusual metal hydride complexes that are available by reduction of M{N(SiMe 3 ) 2 } 3 complexes were described. 33 During this work, two observations for these silylamide complexes became a focus of interest. First, it is notable that while divalent M{N(SiMe 3 ) 2 } 2 complexes have been described for the mid and late transition metals from chromium to nickel (although only as base-stabilized complexes in the case of chromium), no such complexes have been described for titanium or vanadium.…”

Synthesis and Reactivity of Bis-tris(pyrazolyl)borate Lanthanide/Aluminum Heterobimetallic Trihydride Complexes

“…The Ln–N­(κ 3 -Tp) bond distances in 2-Ln are consistent with those of 1-Ln and [Ln­(Tp) 2 ] + in the literature . The Al–N­(N″) bond distances of 1.8430(19)–1.844(3) Å in 2-Ln are similar to those in [ V ] [1.837(2) Å], TM/Al heterobimetallic hydrides containing TM–(μ-H) 2 –Al­(N″) n , and the homoleptic complex [Al­(N″) 3 ] [1.813(3) Å] …”