Volker Pank

Transition metal nitrosyls as nitrosylation agents. IV. 51V NMR characteristics of dinitrosyl and carbonylmononitrosyl vanadium complexes

The action of [Co(X)(NO)2]2 (X = Cl, Br, L) on [V(H)(CO)6−nLn] (L = 1/ndi- and tritertiary phosphine; n = 2, 3) in thf yields [V(CO)5−n(NO)L2] and [V(NO)2(thf)4]X as the two main products. Thf is easilty replaced by other ligands L′, leading to the complexes cis-[V(NO)2(thf)4−nL′n]X, where n = 1 to 4. In the case of L′= CNR (R = Cy, iPr, tBu), the species [VX(NO)2L′3] are formed. The presence of X in the first coordination sphere is established by the normal halogen dependence (Cl < Br < I) of 51V shielding. δ(51V) values have been obtained for the two series of complexes and compared with δ of other nitrosylvanadium species, including [VX(NO)L′4]X. for [V(NO)2L′4]br, 51V shielding increases in the sequence {O} < {S} < NR3 < NCMe < AsEt3 < SbEt3 < PEt2Ph < P(OMe)3 < CNR, reflecting a general increase of shielding as the polarizability of the ligand function increases and its electronegativity decreases. Superimposed effects arising from electronic influences (PEtPh2) < PMe3 < P(OMe)3 and steric conditions (chelate-4 ring < 7 ring < 6 ring < 5 ring) are also discussed. Steric factors are especially pronounced in the [V(CO)3(NO)Ph2P(CH2)mPPh3] series (m = 1–4). The thermo-labile parent compound, [V(CO)5NO], has been characterized by its δ(51V) = −1489 ppm at 245 K.

Carbonylniobium chemistry : III. Tricarbonyl-η5-cyclopentadienylhydridoniobate(−I): Preparation and 93Nb NMR spectroscopic invesitgation of [Et4N][CpNb(H)(CO)3] and [Et4N][CpNb(D)(CO)3]

Abstract The complexes [Et 4 N][CpNb(X)(CO) 3 ] (X = H, D) have been prepared by reduction of CpNb(CO) 4 in THF and subsequent treatment with CX 3 CN/[Et 4 N]Cl. There is IR-spectroscopic evidence for the formation of an intermediate [CpNb(CO) 3 ] 2− . The isotope effect ( 1 H, 2 H) on the 93 Nb shielding (6 ppm) and the temperature dependencies of δ( 93 Nb) (0.25 ppm/deg) and the line widths are discussed.

Alkinylverbindungen von übergangsmetallen : XXXIII. Planare palladium(II)-komplexe mit o-ethinylphenylacetylid-ionen als liganden

Abstract By the reaction of trans-[Pd(PEt 3 ) 2 X 2 ] with solutions of o -diethynylbenzene 1,2-HCCC 6 H 4 CCH in liquid ammonia the complexes trans -[Pd(PEt 3 ) 2 (X)-( o -C 2 C 6 H 4 C 2 H)] (X  Cl, Br, I) have been prepared. The corresponding pseudo-halide complexes trans -[Pd(PEt 3 ) 2 (X′)( o -C 2 C 6 H 4 C 2 H)] X′  NCS, CN) could be formed from these complexes by substitution reactions. The molecular structures of all these complexes have been determined by 31 P and 1 H NMR data, that of the N -thiocyanato complex has been confirmed by X-ray studies. The IR and Raman spectra as well as the dipole moments of the complexes are discussed.