Vanadium complexes dimethyl

The formation of the 17-electron paramagnetic vanadium complex is not surprising in view of the known corresponding carbonyl complex, however the 16-electron titanium derivative is unexpected in view of the ready formation of the 18-electron biscarbonyl and bistrifluorophos-phine metal complexes containing the 5-cyclopentadienyl ligand. The solid-state structure of the PF3 adduct of bis[2,4-dimethyl-(pentadienyl)]titanium has recently been determined (111) and is shown in Fig. 20. The corresponding vanadium complex is isomorphous. The metal-PF3 distances are 2.326(Ti) and 2.275(V) A. 

NCjHi], Ethanamine, 1,1-dimethyl-, tungsten complex, 27 301 NC,Hj, Pyridine, vanadium complex,... 

Cp2V()] -alkene) is synthesized by treatment of vanadocene with aUcene bearing an electron-withdrawing group. The reaction of vanadocene with dimethyl frunarate or dimethyl maleate leads to the formation of the same complex, bis() -cyclopentadienyl)() -dimethyl fumarate)vanadium (72), via isomerization (Scheme 40). 

The ability of phosphines to act as both a metal oxidation states and as a 7r acceptor to relieve electron density from lower metal oxidation states explains, in part, the observation that diphosphines stabilize the +3, +1, and 0 oxidation states at the expense of the +2 oxidation state.870 Vanadium(II) diphosphine halides, [V(dmpe)2X2] (dmpe = dimethyl-dimethylphosphinoethane, X = Br or I), were prepared as side products in the synthesis of [XV(CO)2(dmpe)2].885 The structurally characterized diphosphino V11 tetrahydroborate complex, tra .s-[V(BH4)2(dmpe)2], (223) was synthesized via the reduction of similar vanadium(III) precursors.832 The reaction of a vanadium(II) chloride salt with dmpe afforded the tra s-[VCl2(dmpe)2] complex which can be alkylated with MeLi or MgMe2 to afford the organometallic trans-[V(Me)2(dm pcVJ compound, which in turn reacts with thiocyanate to form tnms -[V(NCS)2(dmpe)2].8 87 Acetonitrile or propionitrile readily displace the chlorides from trans- WCl2(dmpe)2] to form // tf/ ,v-[V( NCR)2(dmpc)2][BI>h4]2 (R = Me or Et) the acetonitrile derivative reacts with HCPh(S02CF3)2 in acetonitrile solvent to yield the hexaacetonitrile species [V(NCMe)6]2+.887... 

Magnetic exchange interactions have also been identified in the oxovanadium-(iv) complexes with the Schiff bases derived from 2-hydroxy-l-naphthaldehyde and ethanolamine or propanolamine. Such complexes can accommodate two further donor atoms per metal and [VO(A)(L)] (A = bipy or phen HjL = Schiff base from salicylaldehyde or 2-hydroxy-l-naphthaldehyde with glycine, alanine, anthranilic acid, or o-aminophenol) complexes have been shown to involve six-co-ordinate vanadium. Similarly, VOL,B [HjL = 2-hydroxy-naphthylideneamino-acid, B = HjO, phen, or (py)2 HjL = 2-hydroxy-naphthylidene-o-aminophenol, B = phen] have normal magnetic moments ifi = 1.70—1.74 BM) at room temperature. The complex VOL (HjL = 6,ll-dimethyl-7,10-diazahexadeca-6,10-diene-2,4,13,15-tetrone) has been prepared from V0(0H)2, heptane-2,4,6-trione, and en in MeOH. The structure... 

In a further spectrophotometric method, the polyester is reacted with a dimethyl formamide monochlorbenzene solution of vanadium 8-hydroxyquinolinate (V8HQ). A coloured complex is formed according to Tanaka and Kojima [9]. 

The synthesis of hexakis(dimethyl sulphoxide)vanadium(m) perchlorate and the kinetics of its reaction with SCN", bipy, and sulphosalicylic acid have been reported. The complex-formation rates show some dependence on the nature of the ligand but a definite mechanistic assignment cannot yet be made. 

Homoleptic solvento-complexes can be prepared by electrochemical oxidation of metals in non-aqueous solvents. For example, [V(DMSO)6][BF4l2 and [In(MeCN)6][BF4]3 have been synthesized25,26 by vanadium or indium oxidation in dimethyl sulfoxide or acetonitrile in the presence of HBF4. Gram quantities of these solvento-complexes may be obtained with yields of 80-90% based on the dissolved metal. 

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