Synthesis and Crystal Structure of Organocobalt(III) Complexes with Secondary Alkyls or Bulky Schiff Base Equatorial Ligands

Abstract

Alkylcobalt(III) Schiff base B(12) model complexes with secondary alkyls or a bulky diamine in the equatorial position were synthesized and characterized. Structures have been first determined by X-ray diffraction analysis for i-C(4)H(9)Co(salen)(gamma-pic) (I), n-C(3)H(7)Co(salen)(gamma-pic) (II) and C(2)H(5)Co(SB) (III), where salen = N,N'-ethylenebis(salicylideneamine) dianion; SB = 1,1,2,2-tetramethyl-N,N'-ethylenebis(salicylideneamine) dianion, gamma-pic = gamma-picoline. Crystal data for I (CoC(26)N(3)O(2)H(30)): space group P2(1)/c with a = 6.661(5) Å, b = 18.612(2) Å, c = 19.533(3) Å, beta = 98.93(1) degrees, V = 2392.10 Å(3), D(calcd) = 1.320 g.cm(-3), Z = 4, and R = 0.048 for 4469 measured reflections. Crystal data for II (CoC(25)N(3)O(2)H(28)): space group P2(1)/c, a = 9.609(6) Å, b = 19.169(8) Å, c = 12.995(9) Å, beta = 106.9(7) degrees, V = 2290.4 Å(3), D(calcd) = 1.332 g.cm(-1), Z = 4, and R = 0.048 for 4358 measured reflections. Crystal data for III (CoC(22)N(2)O(2)H(27)): space group P2(1)/c, a = 8.318(3) Å, b = 21.579(2) Å, c = 11.572(2) Å, beta = 93.35(1) degrees, V = 2073.7 Å(3), D(calcd) = 1.314 g.cm(-1), Z = 4, and R = 0.060 for 3954 measured reflections. The crystal structure data reveal that complexes I and II display six-coordinate octahedral geometry; their Co-C, Co-N bond lengths, as well as the Co-C-C angles, are very close to those in 5'-deoxyadenosylcobalamin. Complex III is one of the very few compounds having five-coordinate square pyramidal geometry and observed instability of the Co-C bond.

Olefinmetathesis as a tool for multinuclear Co(iii)salen catalyst construction: access to cooperative catalysts

“…Although the C-bound acetone complex 5c represents a rather remarkable structure, there are some literature precedents for Co(salen) and/or similar structures bearing stable Co-C bonded axial ligands. 17 These complexes have for instance been used as model compounds for vitamin B12-containing enzymes.…”

Inorganic and organometallic cobaloximes with dioxime containing Se side chain: Synthesis, characterization and comparison with related B12 model compounds

“…The inherently weak CoÀC bond in the organocobaloximes undergoes homolytic cleavage with visible light, similar to the þ0.0314 (11) þ0.0530 (8) þ0.0431 (7) þ0.0479 (9) p•••p (Å) 3.525 (1) 3.5204(9) 2 The torsion angle (s) is the angle between two virtual planes that bisect cobaloxime plane. This shows dihedral angle between the plane of pyridine and the plane bisecting the CeC bond of two dioxime units through the cobalt atom.…”

“…The studies have helped to understand the chemistry and biochemistry of B 12 coenzymes [4e6]. The influence of equatorial ligands (cis influence) in the Schiff base compounds like Co(saloph)R (saloph ¼ dianion of disalicylidene-ophenylenediamine) [7,8], LCo(acacen)R [acacen ¼ dianion of ethylenebis(acetylacetone imine)] [1], LCo(salen)R [salen ¼ dianion of N,N 0 -ethylenebis(salicylideneamine)] [9] and Costa's model [10,11] such as [LCo{(DO)(DOH)pn}R]X [(DO)(DOH)pn, N 2 ,N 2 0 -propanediylbis(2,3-butanedione-2-imine-3-oxime)] has also been reported.…”