Synthesis and Characterization of Six-Coordinate Nitrido Complexes of Vanadium(V), Chromium(V), and Manganese(V). Isolation of a Dinuclear, Mixed-Valent μ-Nitrido Chromium(III)/Chromium(V) Species

Abstract

Photolysis of a series of octahedral monoazido complexes of the type [LM(III)(didentate ligand)(N(3))](n)(+)X(n) of vanadium(III), chromium(III), and manganese(III) in the solid state or in solution yields quantitatively the corresponding six-coordinate nitrido complexes [LM(V)(didentate ligand)(N)](n)(+)X(n) and 1 equiv of dinitrogen. L represents the macrocycle 1,4,7-triazacyclononane or its N-methylated derivative (L'), the didentate ligands are pentane-2,4-dionate (acac), 2,2,6,6-tetramethylheptane-3,5-dionate (tacac), picolinate (pic), phenanthroline (phen), and oxalate (ox), and X(-) represents perchlorate or hexafluorophosphate. The following nitrido complexes were prepared: [LV(V)(N)(acac)](ClO(4)) (6), [LCr(V)(N)(acac)](ClO(4)) (13), [LCr(V)(N)(tacac)](ClO(4)) (14), [LCr(V)(N)(pic)](ClO(4)) (15), [LCr(V)(N)(phen)](ClO(4))(2) (16), [LCr(V)(N)(ox)] (19), [L'Mn(V)(N)(acac)]PF(6) (21). Photolysis of [LCr(III)(N(3))(ox)] (17) in the solid state produces the &mgr;-nitrido-bridged mixed-valent species [L(2)Cr(2)(ox)(2)(&mgr;-N)](N(3)) (18). The structures of the precursor complex [L'Mn(acac)(N(3))]BPh(4) (20), of 13, and of [L'Mn(V)(N)(acac)]BPh(4) (21) have been determined by X-ray crystallography. Complex 13 crystallizes in the orthorhombic space group Pnma, with cell constants a = 27.187(5) Å, b = 9.228(2) Å, c = 7.070(1) Å, V = 1773.7(6) Å(3), and Z = 4; complex 20 crystallizes in the triclinic space group P&onemacr; with a = 14.769(5) Å, b = 16.83(1) Å, c = 16.96(1) Å, alpha = 108.19(5) degrees, beta = 105.06(4) degrees, gamma = 99.78(4) degrees, V = 3719(2) Å(3), and Z = 4; and complex 21 crystallizes in the monoclinic space group P2(1)/n with a = 10.443(3) Å, b = 16.035(4) Å, c = 21.463(5) Å, beta = 95.76(1) degrees, V = 3575.9(14) Å(3), and Z = 4. The Cr(V)&tbd1;N and Mn(V)&tbd1;N distances are short at 1.575(9) and 1.518(4) Å, respectively, and indicate a metal-to-nitrogen triple bond.

A (Nitrido)chromium(V) Function Incorporated in a Keggin‐Type Polyoxometalate: [PW11O39CrN]5– – Synthesis, Characterization and Elements of Reactivity

“…This is not unprecedented in the literature. [69] In the case of the d 1 system [PW 11 O 39 {Re VI N}] 4-, the lack of nitrogen superhyperfine coupling was ascribed to an odd electron primarily localized on the rhenium 5d x 2 -y 2 (d π ) orbital overlapping with 2p π orbitals of the inplane oxygen ligands. [54] The spectrum of 1 recorded at 77 K in a frozen solution revealed an axial system with g Ќ = 1.98 and g ʈ = 1.91.…”

“…Other pseudooctahedral (nitrido)chromium complexes have been shown to display a single d-d transition of low intensity in the range 405-450 nm. [69] …”

Ruthenium complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane for atom and group transfer reactions

“…We reported, in 1994, the isolation, crystal structures, and hydrocarbon oxidation reactions of Ru O complexes [Ru IV (Me 3 tacn)O(bpy)] 2+ [16] and cis-[Ru VI (Me 3 tacn)O 2 (CF 3 CO 2 )] + [17]; these two complexes are potent oxidants/catalysts for alkene epoxidation and alkene cis-dihydroxylation reactions. Wieghardt and co-workers also synthesized and structurally characterized manganese-nitrido complex [Mn V (Me 3 tacn)N(acac)] + , which was reported in 1996 [18]. Subsequently we reported the syntheses and crystal structures of molybdenum/tungsten-carbyne complexes [M(Me 3 tacn)(CPh)(CO) 2 ] + (M = Mo, W) in 1998 [19] and chromium-imido complex cis-[Cr VI (tacn){N(t-Bu)} 2 Cl] + (together with the isolation of cis-[Cr VI (Me 3 tacn){N(t-Bu)} 2 Cl] + ) in 1999 [20].…”

“…a acac, pentane-2,4-dionate; biqn, 1,1 -biisoquinoline; bpy, 2,2 -bipyridine; cbpy*, (−)-3,3 -[(4S-trans)-1,3-dioxolane-4,5-dimethyl]-2,2 -bipyridine; diopy*, (R,R )-3,3 -(1,2-dimethylethylenedioxy)-2,2 -bipyridine; 3,3 -Me2bpy, 3,3 -dimethyl-2,2 -bipyridine; phen, 1,10-phenanthroline. b [20,40,41], -carbene/-vinylidene/-allenylidene [42,43], -nitrido [18,44], and -carbyne [19] complexes, is depicted in Table 1.…”

Synthesis, characterization and charge-transfer photochemistry of trans-aquo azido-N,N?-trimethylenebis(naphthylideneiminato)chromium(III)

“…All these complexes are five-coordinate with a square-pyramidal coordinate ion in which the terminal nitrido ligand occupies the apical position [17]. Recently, Wieghardt et al [18] published the first distorted octahedral nitrido chromium(V) complexes of bidentate ligands like oxalate, acetonyl acetate, 2-picolinate or o-phenanthroline. Most of these complexes have no detectable d-d transition in their electronic spectra because of the fact that all auxiliary ligands employed so far display intense charge-transfer bands in the region where the weak d-d transitions are expected to appear [19].…”