Note New chiral terpene-derived vanadatranes Gabriele Wagner a, *, Rudolf Herrmann b , Armando J.L. Pombeiro c a Department of Chemistry, University of Surrey, Guildford GU2 7XH, UK b Instituto de Tecnologia Quı ´mica e Biolo ´gica, Av. da Repu ´blica (EAN), Apartado 127, 2781-901 Oeiras, Portugal c Instituto Superior Te ´cnico, Centro de Quı ´mica Estrutural, Av. Rovisco Pais, 1049-001 Lisboa, Portugal Received 21 November 2001; accepted 13 February 2002 Abstract The synthesis of three new chiral vanadatranes by reaction of oxovanadium(V) alcoholates with triethanolamine derivatives obtained from the terpenes ( /)-b-pinene, ( /)-limonene, and ( /)-menthone is reported. Their structure is elucidated by NMR spectroscopy ( 1 H, 13 C, 15 N, 17 O, 51 V). # 2002 Elsevier Science B.V. All rights reserved. Keywords: Chiral vanadatranes; Terpene derivatives; NMR spectroscopy ( 1 H, 13 C, 15 N, 17 O, 51 V) 1. Introduction Derivatives and analogues of triethanolamine often form cage compounds with both main group and transition metals. Such compounds have been called atranes (in the case of vanadium, vanadatranes). The parent compound vanadatrane was first obtained from triethanolamine and oxovanadium(V) alcoholates by Voronkov et al. [1] and shows interesting structural properties: it is a stable monomeric vanadium(V) alk- oxide and not prone to oligomerization reactions as most oxovanadium alkoxides are when concentrated or crystallized. Only very few chiral vanadatranes have been reported up to now; in these cases, one of the hydrogen atoms in all three CH 2  /O groups of triethanolamine has been replaced by an alkyl or phenyl substituent. However, most of these compounds have been obtained solely in racemic form [2], and thus only four homochiral (optically active) vanadatranes are known [3]. In this work, we whish to present three new enantiopure chiral vanadatranes which are easily accessible from terpenes from the chiral pool. The ligands 2a, 2b and 2c were prepared by ring opening of the corresponding homo- chiral epoxides 1a, 1b or 1c with diethanolamine as previously described [4]. Their reaction with triethoxy vanadate in ethanol solution occurs smoothly at room temperature to give the corresponding vanadatranes 3a, 3b and 3c as air-stable colourless to pale yellow solids (Fig. 1). The vanadatranes were fully characterized by the usual techniques (microanalysis, mass spectrometry, IR and NMR spectroscopy). The presence of the oxovana- dium(V) unit is clearly reflected in the typical IR signals at 955  /965 (V /O) and 630  /635 (V  /O) cm 1 [2]. The existence of the V  /N bond is shown by the close analogy of the 51 V, 17 O, and 15 N NMR data when compared with other vanadatranes whose crystal struc- ture [2,3] is known. Thus, simple oxovanadium(V) alcoholates show a highly shielded vanadium atom in organic solvents (OV(OEt) 3 : d  /598 [5]; OV(OPr i ) 3 : d  /628 [6]), while the vanadatranes 3 (d  /380.6,  /400.4, and  /392.7, respectively) compare well with the un- substituted parent compound (d  /383.5 [2]). 15 N and 17 O NMR data were determined for the limonene- derived compound 3a. The nitrogen chemical shift (d 59.2, CDCl 3 ) is clearly distinguished from the uncoor- dinated ligand (d 26.4) and reflects the presence of the vanadium  /nitrogen bond, just as in the parent vanada- trane (d 54.8, d 6 -DMSO) and the corresponding free ligand triethanolamine (d 24.7) [7]. The 15 N / 51 V coupling is not resolved in the vanadatranes, but a coupling to the hydrogen atoms of the neighbouring methylene groups can be observed (5.5 Hz; parent vanadatrane: 3.2 Hz [7]). Up to now, 17 O NMR data of vanadatranes have always been measured in D 2 O * Corresponding author. Tel.:  /44-1483-686 831 Inorganica Chimica Acta 336 (2002) 147  /150 www.elsevier.com/locate/ica 0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0020-1693(02)00847-2