ChemInform Abstract: SYNTHESIS AND MOLECULAR STRUCTURE OF THE NIOBOCENECARBONYLHYDRIDE ADDUCT TO BIS(TETRAHYDROBORATE)ZINC

Abstract

Das Addukt (I) wurde durch Reduktion von NbCls mit Zn‐Metallpulver in Gegenwart von Na‐cyclopentadienid in THF unter CO bei Raumtemp. und nachfolgende Behandlung mit NaBH4 dargestellt und durch IR‐ und NMR‐ Daten, sowie Kristallstrukturbestimmung (Raumgruppe Pl, Z=2) charakterisiert.

Accuracy of multidetector computed tomography in identifying poor prognostic factors in colonic cancer

“…To the best of our knowledge, besides the [Zn(BH 4 ) 3 ] − anion5 and methylzinc tetrahydroborate (MeZnBH 4 )6 only four other ZnBH 4 compounds have been reported. These are [(η 5 ‐C 5 H 5 ) 2 NB(CO)HZn(BH 4 ) 2 ],7 [Zn(η 2 ‐BH 4 )Cl(tmen)] (tmen= N,N,N′,N′ ‐tetramethylenediamine),8 the bimetallic vanadium(I) polyhydride [(PMePh 2 ) 4 V 2 H 4 {Zn(BH 4 )} 2 ]9 and the β‐diketoiminate complex [(dipp)NacNacZn(η 2 ‐BH 4 )] ((dipp)NacNac=2‐[(2,6‐diisopropylphenyl)amino]‐4‐[(2,6‐diisopropylphenyl)imino]pent‐2‐enyl) 10. Besides these ZnBH 4 compounds, the methylzinc hydroborate derivative [(MeZn) 2 B 3 H 7 ] 2 11 and the adduct ZnCl 2 ⋅ B 2 H 4 ⋅ 2P(CH 3 ) 3 12 are known.…”

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“…In the first a chelating trans-B 2 H 4 -(PMe 3 ) 2 ligand is bound to a ZnCl 2 unit via two hydride bridges (23), the positions of which deviate little from the plane of the ZnB 2 framework. 414 The Zn-(µ-H) distances [1.89(5) Å on average] are not significantly different from those found in zinc tetrahydroborate derivatives, although there is a considerable opening up of the H-Zn-H angle {107(2)°f or Cl 2 Zn[η 2 -B 2 H 4 (PMe 3 ) 2 ]; 54-70°for zinc tetrahydroborates [406][407][408][409]411 }, reflecting the very different bite angles of the BH 4 and B 2 H 4 (PMe 3 ) 2 ligands. [(MeZn) 2 B 3 H 7 ] 2 features discrete centrosymmetric Me 4 Zn 4 B 6 H 14 dimers in which two novel B 3 H 7 ZnMe ligands are linked through hydride bridges about a central MeZn‚‚‚ZnMe vector [3.014(3) Å] in an unusual example of a molecule containing two distinct zinc environments.…”

“…The geometry of the Zn(µ-H) 2 BH 2 unit varies little among the four crystallographically characterized species containing a terminal BH 4 moiety, viz. [(MePh 2 P) 2 VH 2 Zn-(BH 4 )] 2 , 406 [Cp 2 Nb(CO)(µ-H)Zn(BH 4 )] 2 , 407 (tmeda)Zn-Cl(BH 4 ) 408 6). The average Zn‚‚‚B distance (2.25 Å) is somewhat greater than the sum of the covalent radii of zinc and boron (2.15 Å 391 ), in support of the view that direct Zn‚‚‚B interactions play but a minor role in the bonding of the Zn(µ-H) 2 BH 2 fragments.…”

“…The geometry of the Zn(μ-H) 2 BH 2 unit varies little among the four crystallographically characterized species containing a terminal BH 4 moiety, viz. [(MePh 2 P) 2 VH 2 Zn(BH 4 )] 2 , [Cp 2 Nb(CO)(μ-H)Zn(BH 4 )] 2 , (tmeda)ZnCl(BH 4 ) (tmeda = Me 2 NCH 2 CH 2 NMe 2 ), and [Ph 4 P][Zn(BH 4 ) 3 ] . Averaging 1.85 Å, Zn−(μ-H) distances are ca.…”