J. Roger Sanders

Non-planar co-ordination of the Schiff-base dianion N,N′-2,2-dimethyltrimethylenebis[salicylideneiminate(2–)] to vanadium

The Schiff-base dianion N,N′-2,2-dimethyltrimethylenebis[salicylideneiminate(2–)](salnptn) coordinates to vanadium(IV) to form [VO(salnptn)] whose crystal structure has been determined. The compound is polymeric in the solid state with ⋯ VO → VO → VO ⋯ chains, the salnptn donor atoms being coplanar and the salnptn framework umbrella-shaped. In the derivative [VO(OMe)(salnptn)], the crystal structure of which has also been determined, the OMe and the vanadyl oxygen are co-ordinated cis to each other, and the salnptn now occupies three equatorial and one axial co-ordination positions. Even N,N′-ethylenebis(salicylideneiminate) seems to behave analogously, though it is normally planar.

New polymeric compounds containing vanadium–oxygen chains

The controlled protonation of complexes of tetradentate Schiff-base anions, L2–, [VO(L)], has been found to yield [V(OH2)(L)]2+, [V(L)OV(L)]2+, [V(L)OV(L)OV(L)]2+ or [V(L)OV(L)OV(L)OV(L)]2+, depending on reaction conditions. The crystal structures of two salts of the last where L =N,N′-ethylenebis(salicylideneiminate) have been determined, and compared with those of the known [V(L)OV(L)O]+ and the new [{V(L)OV(L)}2]2+. These compounds are the first members of what appears to be an extensive family of compounds containing vanadium–oxygen chains.

Novel binuclear vanadium(V)–Schiff base cations containing single fluorine bridges and the structure of difluorodioxovanadate(1–)

The complex [VO (salen)][H2salen =N,N′-ethylenebis(salicylideneimine)] reacted with HBF4·Et2O in air to produce the novel linear species [{VO (salen)}2(µ-F)]+, the structure of which has been determined as its BF4– and [VO2F2]– salts. The perchlorate and triflate (O3SCF3)– salts have been characterised spectroscopically and analytically, as well as the tetrafluoroborate homologues from salicylaldehyde and 2-methylpropylenediamine, and from ethylenediamine and 3-methoxysalicylaldehyde. The [VO2F2]– is mononuclear in the above salt, as well as in [PPh4][VO2F2], compared to a polynuclear form found in [NH4][VO2F2]. The mononuclear anion was also fully characterised by 19F and 51V NMR spectroscopy.

The protonation of bridging dinitrogen to yield ammonia

The protonation of the VII bridging dinitrogen complex [{V(C6H4CH2NMe2)2(C5H5N)}2N2] yields 2/3NH3, 2/3N2 and unidentified VIII-containing products, although hydrazine might have been expected on the basis of its structure; another factor influencing the product of dinitrogen protonation appears to be the availability of electrons from the metal atoms.

Synthesis and structure of a thiolate-bridged nickel–iron complex: towards a mimic of the active site of NiFe-hydrogenase

The reaction, under carbon monoxide, of [Fe(NS3)(CO)]– [NS3 = N(CH2CH2S)33–] with [NiCl2(dppe)] gives the structurally characterised dinuclear thiolate-bridged complex [{Fe(NS3)(CO)2-S,S′}NiCl(dppe)], which has structural features similar to those of the active site of NiFe-hydrogenase.

Crown thioether complexes of vanadium(II), vanadium(III) and vanadium(IV): X-ray crystal structure of [VCl3([9]aneS3)]

The synthesis of macrocyclic thioether complexes of vanadium(II), vanadium(III) and vadium(IV) and the X-ray structure of [VCl3([9]aneS3)] are described.

Crystal and molecular structure of the compound [(salen) VOVO(salen)][I5]·MeCN [salen =N,N′-ethylene-bis(salicylideneiminate)] and the preparation of similar complexes with other Schiff-base ligands

The oxidation of [VO(salen)][salen =N,N′-ethylenebis(salicylideneiminate)] with iodine produces a mixed vanadium(IV)–vanadium(V) species containing [(salen)VOVO(salen)]+ and the counter ion I5–, as determined by X-ray crystal-structure analysis. The oxidation of related vanadyl Schiff-base complexes produces similar species. Magnetic and spectroscopic properties of these new complexes are described.

The preparation and structure of [Vl2(salen)]·CH2Cl2[salen =N,N′-ethylenebis(salicylideneiminate)(2–)] and of some homologues of related Schiff bases

The elusive [Vl2(salen)][salen =N,N′-ethylenebis(salicylideneiminate)(2–)] and some of its homologues have been successfully prepared. The structure of [VI2(salen)]·CH2Cl2 has been determined by X-ray crystallography, and the conformation is trans-octahedral, as expected, with long V–I separations. The complex is air-stable in the solid state, but appears to be moisture-sensitive in solution, and undergoes autoredox reactions (VIV→VIII, I–→I2) in ionising solvents.

Reactions of vanadium(IV) halide complexes containing Schiff-base ligands with hydrazines; preparation and structure of [N,N′-ethylenebis(salicylideneiminato)]bis-(phenylhydrazine)vanadium(III) iodide

The complexes [VX2L][L =N,N′-ethylenebis(salicylideneiminate)(salen) or N,N′-1,2-phenylenebis-(salicylideneiminate)(salphen), X = Cl or Br] have been prepared by established routes, but attempts to prepare the iodo-analogue led to other products, including [(salen)V(µ-O)VO(salen)][I5]. It is not possible to prepare hydrazine or hydrazide complexes directly from the dihalides, but [V(NH2NHPh)2(salen)]I was synthesised by an indirect route, and its structure determined by X-ray analysis. The phenylhydrazines are bound end-on. Several other new vanadium-(III) and (IV) species are described.

A linear tetranuclear vanadium-oxygen assembly

The reaction of [VO(salen)] with controlled quantities of species able to extract the oxygen atom, such as trityl fluoroborate or fluoroboric acid–diethyl ether (1/1) leads to the novel tetranuclear cation [{V(salen)}4(µ-O)3]2+, which contains a linear vanadium–oxygen chain.