John D. Wilkins

The reactions of isocyanates and isonitriles with methylniobium(V) chlorides and methyltantalum(V) chlorides

The reactions of MexMCl5−x(x = 1, 2, 3, M = Nb, Ta) with RNCO (R = Me, Ph) have been studied and products of the types MCl3[NRC(O)Me]2, MeMCl2[NPhC(O)Me]2, MeTaCl2[NMeC(O)Me]2 and TaCl2[NMeC(O)Me]3 containing acetamide groups arising from insertion of the isocyanate into the mealcarbon bonds have been characterised. The complexes MeTaCl2[C(Me)NR]2 (R = cyclohexyl, p-tolyl) have been isolated from the reactions of Me3TaCl2 with RNC.

Reactions of methylniobium(V) and methyltantalum(V) chlorides with carbodiimides

Abstract The chlorides MexMCl5-x, M = Nb, Ta, x = 1, 2, 3 react with carbodiimides RNCNR (R = isopropyl, cyclohexyl, p-tolyl) to give products of the types MCl4[NR-C(Me)=NR], MeMCl3[NR-C(Me)=NR], MCl3[NR-C(Me)=NR]2, Me2MCl2[NR-C(Me)=NR], MeMCl2[NR-C(Me)=NR]2, which contain bidentate acetamidine groups arising from insertion of the carbodiimide into the metal-carbon bond. The products have been characterised by elemental analysis IR and proton NMR spectra.

The reactions of isothiocyanates and thiocyanates with methylniobium(V) chlorides and methyltantalum(V) chlorides

Abstract The reactions of Me x MCl 5− x , x = 1,2,3, M = Nb, Ta with RNCS, R = Me, Ph have been studied, and products of the types MCl 4 [NRC(S)Me], MeTaCl 3 [NRC(S)Me] and NbCl 3 [NMeC(S)Me] 2 containing thioacetamide groups, arising from insertion into the metalcarbon bonds have been characterised. Reactions with MeSCN yield the complexes MeMCl 4 · MeSCN and Me 2 MCl 3 · MeSCN; the presence of S- and N-bonded isomers is indicated by the infrared spectra.

The reaction of methylniobium(V) and methyltantanium(V) chlorides with nitrogen oxide and the crystal and molecular structure of one of the products, methyldicholorobis(N-methyl-N-nitrosohydroxylaminoto) tantalum(V)

Abstract The reaction of NO with Me 2 MCl 3 and Me 3 MCl 2 (M = Nb, Ta) yields complexes MCl 3 [ON(Me)NO] 2 and MeMCl 2 [ON(Me)NO] 2 respectively. The complexes have been characterised by measurements of IR and NMR spectra; the reactivity of the methyl group in the complex MeTaCl 2 [ON(Me)N0] 2 is discussed. Crystals of this compound are monoclinic, spacegroup P 2 1 / n with α = 9.78(1), b = 15.10(1), c = 7.74(1) A, β = 97.18(6)°, Z = 4. 1336 independent intensities were measured by counter methods and the structure refined to R 0.087. The co-ordination sphere of the tantalum atom is a slightly distorted pentagonal bipyramid with two chlorine atoms in axial positions [2.359(8), 2.357(10) A]; four oxygens [2.090(17), 2.081(21), 2.108(18), 2.066(26) A] and one methyl group [2.248(28) A] in the pentagonal girdle.

Reactions of methylniobium(V) and methyltantalum(V) chlorides with ketones

Abstract The reactions of MexMCl5-x (M = Nb, Ta, x = 1, 2) with a variety of ketones have been investigated. Bulky ketones give complexes of the type MexMCl5-x· RR′CO for R = R′ = cyclohexyl; R = Me, R′ = t-Bu; R = Me, R′ = neopentyl. Addition of the methylmetal group to the carbonyl group takes place with less bulky ketones and benzaldehyde. Reactions with oxygen and γ-picoline-N-oxide have also been investigated.

Crystal and molecular structure of tetracarbonyliodo-[o-phenylenebis(dimethylarsino)] tungsten(II) triiodide

Crystals of the title compound are monoclinic, spacegroup P 2 1 / m ; a = 14.43(1), b = 10.86(1), c = 8.01(1) A β = 93.51(8)°; Z = 2. The structure was solved from diffractometer data by Patterson and Fourier methods and refined by least squares to R 0.07 for 1544 independent reflections. The cations have crystallographic m symmetry with the metal and iodine atoms on the mirror plane. The metal atom has a capped trigonal prismatic environment with the iodine atom in the unique capping position [2.842(3) A], two arsenic atoms [2.636(2) A] and two carbonyl groups [2.067(24) A] in the capped quadrilateral face and two carbonyl groups [1.988(25) A] in the remaining edge. The distortions of the geometry from the ideal are very small despite the variations in ligand type in the quadrilateral face. The triiodide anion is asymmetrical with dimensions [2.895(3), 2.957(4) A, 178.6(1)°].

Some reactions of di-π-cyclopentadienyllead(II)

Abstract (C 5 H 5 ) 2 Pb reacts with HX to give (C 5 H 5 )PbX or PbX 2 , X = Cl,Br,CH 3 CO 2 , with BF 3 ·Et 2 O to give (C 5 H 5 ) 2 PbBF 3 and with TCNE to give (C 5 H 5 ) 2 Pb·O·5TCNE or (C 5 H 5 ) 2 Pb·TCNE.

Insertion and related reactions of bis(η-cyclopentadienyl)dimethyltitanium, η-cyclopentadienyltrimethyltitanium, and trichloro(η-cyclopentadienyl)titanium and other titanium compounds

The reaction of [(cp)2TiMe2] with cyclohexyl isocyanide (C6H11NC) yields the complex [(cp)2TiMe{C(Me):NC6H11}], which further reacts with iodine to give the complex [(cp)2Til{C(Me):NC6H11}]. The reactions of [(cp)TiMe3] with NO, SO2, RNC (R = C6H11 or p-tolyl), MeNCO and PhNCS have been studied and the complexes [(cp)TiMe{ON(Me)NO}2] and [(cp)TiMe2(SO2Me)] have been isolated and characterised. The reactions of [(cp)TiCl3] and [(cp)TiMe3] with Lewis bases have been studied and the complexes [(cp)TiCl3(diars)] and [(cp)TiCl3(bipy)] isolated [diars =o-phenylenebis(dimethylarsine), bipy = 2,2′-bipyridyl]. The complexes [(cp)2TiBr(OCH2CH2CH:CH2)] and [(cp)TiMe2(OCH2CH2CH:CH2)] have been prepared and it has been shown that the olefinic group is not co-ordinated to the titanium atom in either case. Attempts to co-ordinate the olefinic grouping of the ligand Me2N·CH2·CH2·N(Me)·CH2·CH2·CH:CH2 to titanium tetrachloride and titanium trichloride are also described.

Crystal and molecular structure of trichlorobis-(NN′-di-isopropylacetamidinato)tantalum(V)

Crystals of the title compound are monoclinic, space group P21/a with a= 17·420(8), b= 11·924(8), c= 11·027(8)A, β= 95·88(8)°, Z= 4. The structure was solved by Patterson and Fourier methods from diffractometer data and refined by least-squares techniques to R 0·064 for 2003 independent reflections. The seven-co- ordinate monomer is a highly distorted pentagonal bipyramid with two chlorine atoms in axial positions [2·386(6), 2·370(6)A], one chlorine [2·436(6)] and four nitrogens [2·098(14), 2·193(16), 2·180(20), and 2·058(16)A] occupying the pentagonal girdle. There are many close contacts involving the isopropyl groups which cause considerable distortion to the polyhedron. The maximum deviation of a contributing atom from the least-squares plane of the TaClN4 unit is 0·33 A.

Crystal and molecular structure of dicarbonylchlorobis-[o-phenylene(dimethylarsino)]molybdenum(II) tri-iodide–bischloroform

Crystals of the title compound are orthorhombic, space group Pnma, with a= 11·75(1), b= 15·27(1), c= 24·15(2)A, Z= 4. The structure was solved by the heavy-atom method from 1048 independent reflections, collected by counter methods, and refined by full-matrix least-squares techniques to R 0·080. The symmetry of the cation is very close to C2v(mm) with one of the mirror planes imposed by the space group. Thus the molybdenum atom has a 1,4,2-capped trigonal prismatic environment with a chlorine atom in the unique capping position [2·575(11)A], four arsenic atoms in the capped quadrilateral face [2·614(5), 2·617(5)A], and two carbonyl groups making up the remaining edge [1·92(5), 1·87(5)A]. The tri-iodide ion lies with the central atom on a crystallographic mirror plane [2·903(2)A, 176·9(2)°].