Studies on amavadin and related chemical systems.

New molybdenum(v) analogues of Amavadin and their redox properties

“…These spectra closely resemble the UV/vis spectrum obtained for [PPh 4 ]-[∆-Mo(R,R-hidpa)(R,S-hidpa)]. 13 By analogy with the electronic structure proposed for Amavadin and related systems from discrete variational (DV) Xα calculations, 34 these transitions are assigned as d x 2 Ϫ y 2 d yz , d xz and d x 2 Ϫ y 2 d xy , respectively. This interpretation suggests an "electronic equivalence" between two mutually trans and perpendicular η 2 -NO groups and one terminal oxo group.…”

New vanadium-(IV) and -(V) analogues of Amavadin ‡

“…The two ethyl groups attached to same ligand at the C(6) and C(7) atoms are approximately The two Ca 2ϩ centres in the asymmetric unit of 1 are each seven-co-ordinate (Fig. 3), containing two co-ordinated H 2 O molecules [Ca(1)᎐O (21) and ᎐O (22), Ca(2)᎐O (23) and ᎐O(24)], three unidentate carboxylates [Ca(1)᎐O (12), ᎐O(4*) and ᎐O(7*), Ca(2)᎐O(2), ᎐O(14*) and ᎐O(17*)] and a bidentate carboxylate group [Ca(1)᎐O (9) and ᎐O (10), Ca(2)᎐O (19) and ᎐O( 20)], see Table 3 for bond lengths. The O (10) and O (20) oxygen atoms in the bidentate carboxylates are simultaneously bound to the vanadium and calcium centres, where O(10) bridges V(1) and Ca (1) and O(20) bridges the V(2) and Ca(2) atoms.…”

“…3), containing two co-ordinated H 2 O molecules [Ca(1)᎐O (21) and ᎐O (22), Ca(2)᎐O (23) and ᎐O(24)], three unidentate carboxylates [Ca(1)᎐O (12), ᎐O(4*) and ᎐O(7*), Ca(2)᎐O(2), ᎐O(14*) and ᎐O(17*)] and a bidentate carboxylate group [Ca(1)᎐O (9) and ᎐O (10), Ca(2)᎐O (19) and ᎐O( 20)], see Table 3 for bond lengths. The O (10) and O (20) oxygen atoms in the bidentate carboxylates are simultaneously bound to the vanadium and calcium centres, where O(10) bridges V(1) and Ca (1) and O(20) bridges the V(2) and Ca(2) atoms. The angles subtended at the Ca atoms by adjacent Ca᎐O bonds range from 51.9(2) to 118.7(3)Њ for Ca(1) and 51.8 (2) to 21) Ca( 1)᎐O( 22) Ca( 1)᎐O( 12) Ca( 1)᎐O(4*) Ca( 1)᎐O(7*) Ca( 1)᎐O( 9) Ca( 1)᎐O( 10) Ca( 2)᎐O( 23) Ca( 2)᎐O( 24) Ca( 2)᎐O( 2) Ca( 2)᎐O(14*) Ca( 2)᎐O(17*) Ca( 2)᎐O( 19) Ca( 2)᎐O( 20 11) Ca( 1)᎐O( 12) Ca( 1)᎐O( 13) Ca( 1)᎐O( 14) Ca( 1)᎐O( 15) Ca( 1)᎐O( 4) Ca( 1)᎐O( 7 118.8(3...…”

“…The angles subtended at the Ca atoms by adjacent Ca᎐O bonds range from 51.9(2) to 118.7(3)Њ for Ca(1) and 51.8 (2) to 21) Ca( 1)᎐O( 22) Ca( 1)᎐O( 12) Ca( 1)᎐O(4*) Ca( 1)᎐O(7*) Ca( 1)᎐O( 9) Ca( 1)᎐O( 10) Ca( 2)᎐O( 23) Ca( 2)᎐O( 24) Ca( 2)᎐O( 2) Ca( 2)᎐O(14*) Ca( 2)᎐O(17*) Ca( 2)᎐O( 19) Ca( 2)᎐O( 20 11) Ca( 1)᎐O( 12) Ca( 1)᎐O( 13) Ca( 1)᎐O( 14) Ca( 1)᎐O( 15) Ca( 1)᎐O( 4) Ca( 1)᎐O( 7 118.8(3)Њ for Ca(2) (Table 4). The most acute angles occur at the binding sites of bidentate carboxylate groups [O( 9)᎐Ca(1)᎐ O (10) and O( 19)᎐Ca( 2)᎐O( 20)] and the largest angles are subtended by the adjacent carboxylate oxygen atoms from different anions [O( 9)᎐Ca( 1)᎐O (12) and O( 2)᎐Ca( 2)᎐O( 19)].…”

Synthesis and structures of niobium(V) and tantalum(V) analogues of Amavadin: [M(hida)2]− (M = NbV or TaV, H3hida = hydroxyimino-diacetic acid) and [Nb(R,R-hidpa)2]− [H3hidpa = 2,2′-(hydroxyimino)dipropioni c acid]

“…4, 5 The [V(hida) 2 ] 2Ϫ/Ϫ (H 3 hida = hydroxyiminodiacetic acid) analogues have also been shown to exhibit the same Amavadin-style eight-co-ordination. 4,[6][7][8][9] The unusual geometry and chemical behaviour of Amavadin has generated curiosity as to whether it is possible to extend this chemistry to include other metals. The first reported example of a chemical analogue of Amavadin was [∆-Mo(R,R-hidpa)(R,S-hidpa)] Ϫ and its enantiomer, 10 where molybdenum() is bound to two mutually trans η 2 -NO groups and four unidentate carboxylate groups and is capable of both a one-electron reversible oxidation and a one-electron reversible reduction.…”