Pentamethylcyclopentadienyl Halfsandwich Complexes of Vanadium and Tantalum with Amido‐, Imido‐ Nitrido‐ and Azido Ligands

Abstract

Lithium bis(trimethylsilyl)amide, LiN(SiMe3)2, reacts with Cp*V(O)Cl2 and Cp*TaCl4 to give trimethylsilylimido complexes such as [Cp*V(NSiMe3)(μ‐NSiMe3)]2 (7) and Cp*Ta(Cl)(NSiMe3)[N(SiMe3)2] (19), respectively. Substitution of the chloro ligand in 19 by anionic groups leads to complexes with 3 different N‐containing ligands, Cp*Ta(X)(NSiMe3)[N(SiMe3)2] (X = N3 (20) or NPEt3 (21)). Complex 7 is air‐ and moisture‐sensitive, and several derivatives containing oxo and trimethylsiloxy ligands have been identified. Trimethylsilyl azide, Me3Si‐N3, is able to replace the oxygen‐containing ligands for azido ligands. The two complete series of bis(azido)‐bridged complexes, [Cp*VCln(N3)2‐n(μ‐N3)]2 (n = 2, 1, 0) and [Cp*TaCln(N3)3‐n(μ‐N3)]2(n = 3, 2, 1, 0), are accessible from the reactions of Cp*VCl3 and Cp*TaCl4, respectively, with trimethylsilyl azide. A bis(nitrido)‐bridged azido‐vanadium complex, [Cp*V(N3)(μ‐N)]2 (18), has also been obtained and structurally characterized.

First Structural Characterization of Binary AsIIIand SbIIIAzides

“…This is in disagreement with the data previously reported for this compound, d = À 318.0 (N a ), À131.1 (N b ), and À165.2 ppm (N g ). [1,16] However, the observed 14 N NMR resonances for Sb(N 3 ) 3 of d = À324.5 (Dn1 = 2 = 139 Hz, N a ), À136.2 (Dn1 = 2 = 18 Hz, N b ), and À172.3 ppm (Dñ ß = 23 Hz, N g ) are in good agreement with the data reported previously. [2] Theoretical calculations: Geometry optimizations were performed for As(N 3 ) 3 and Sb(N 3 ) 3 by using second-order perturbation theory methods (MP2, also known as MBPT (2)).…”

“…Also, the bridges in Sb(N 3 ) 3 are much stronger (2.844 ä, while the sum of the covalent van der Waals radii is 3.66 ä) than those in As(N 3 ) 3 (2.970, 3.069, and 3.198 ä, while the sum of the covalent van der Waals radii is only 3.40 ä). 14 N NMR spectra: As expected for covalently bonded azides, [4] three well-resolved resonances were found for both compounds in their 14 N NMR spectra in CH 2 Cl 2 at 25 8C. The As(N 3 ) 3 molecule shows a very broad signal at d = À290 ppm (Dn1 = 2 = 300 Hz) for the N a atoms, a sharp signal at d = À145.3 ppm (Dn1 = 2 = 14 Hz) for the N b atoms, and a medium-sharp resonance at d = À175.9 ppm (Dn1 = 2 = 34 Hz) for the N g atoms.…”

“…[14] In our opinion, these unusually short distances are not real and are due to partial occupancy of some azide sites by other atoms, such as chlorine.…”

Formation and Reactivity of the Terminal Vanadium Nitride Functionality

“…[41,47] In a related half-sandwich complex, [(C 5 Me 5 )V(N 3 ) 2 ](μ 2 -1,1-N 3 ) 2 , the 1,1-end-on bridging azide ligands readily convert to the bridging nitride species, [(C 5 Me 5 )V(μ 2 -N)(N 3 )] 2 , at room temperature. [64] Therefore, to test whether a bridging azide ligand is critical en route to nitride formation, we relied on a double crossover experiment, using mononuclear azide complex 1.…”

Tetra-μ3-iodido-tetrakis[(tri-n-butylphosphane-κP)copper(I)]

“…For general background to this work, see: Ainscough et al (2001); Alyea et al (1985); Baker et al (1994); Barron et al (1984); Bowmaker et al (1989Bowmaker et al ( , 1992Bowmaker et al ( , 1994Bowmaker et al ( 1999Bowmaker et al ( , 2002; Churchill & Kalra (1973, 1974; Churchill, DeBoer & Donovan (1975) ;Churchill, DeBoer & Mendak (1975); Churchill & Rotella (1977, 1979; ; ; Gill et al (1976); Goel & Beauchamp (1983); Hadjikakou et al (1993); Herberhold et al (2003); Hermann et al (2001); Jansen (1987); Krause (2002); Mann et al (1936); Medina et al (2005); Moers & Op Het Veld (1970); Ramaprabhu et al (1993Ramaprabhu et al ( , 1998; Schwerdtfeger et al (2004); Soloveichik et al (1992); Wells (1936); Whitesides et al (1971). The CuÁ Á ÁCu distance is markably short as compared with the reported distances of other tetranuclear copper phosphane complexes (Medina et al, 2005).…”