COMMUNICATIONS Angew. Chem. Int. Ed. 1999, 38, No. 9  WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999 1433-7851/99/3809-1261 $ 17.50+.50/0 1261 [(Ph) 2 (NMe 2 )C(OLi) ´ THF] 2 : Crystal Structure of the Tetrahedral Intermediate Formed in the Reaction of N,N-Dimethylbenzamide and Phenyllithium** Martin Adler, Michael Marsch, Norma Sbarbati Nudelman, and Gernot Boche* Dedicated to Professor Reiner Sustmann on the occasion of his 60th birthday The tetrahedral intermediate RC(OH)XY (3) formed in reactions of carboxylic acid derivatives RC(O)X (1) with nucleophiles YH (2) to give RC(O)Y (4 ; Reaction a in Scheme 1) is of continued interest, for example, because of its significance for in vivo acylation rections. [1] Only recently, the solid-state structure of the (protonated) intramolecular amine adduct of a carboxylic acid was determined in a rather special case. [2] Similarly, reactions of 1 with organometallic compounds R'M(5) proceed via a tetrahedral intermediate 6 (Reaction b in Scheme 1). In the case of X  Hal, SR, and OR, 6 Scheme 1. Reaction of carboxylic acid derivatives 1 with nucleophiles YH (2 ; a) and R'M(5 ; b). R  H, alkyl, aryl; X  Hal, SR, OR, NR 2 ; YH  R''SH, R''OH, R''NH 2 ;R''  H, alkyl, aryl; R'  alkyl, aryl; M  Li, MgX, etc. undergoes a very fast 1,2-elimination of MX to give aldehyde or ketone 7 , which may react further with 5. In the case of X  NR 2 , 6 is more stable, a fact that has been utilized for the preparation of ketones 7 (1  5 !6 ; 6  H 3 O  !7) [3] as well as for the protection of aldehydes and ketones (7  MNR 2 !6). [4] What is the structure of a compound of type 6, and in particular what is the environment at the new tetrahedral carbon atom? The X-ray crystal structure of [(Ph) 2 (NMe 2 )C(OLi) ´ THF] 2 (10), [5] which is prepared from N,N-dimethylbenzamide (8) and phenyllithium (9) and crys- tallized from tetrahydrofuran/diethyl ether [Eq. (1) ] , gives an answer to these questions (Figure 1). Figure 1. Crystal structure of 10. Important bond lengths [pm] and bond angles [8]: C1 O1 137.1(2), C1 N1 150.0(3), C1 C4 154.8(3), C1 C10 154.9(3), Li1 N1 375.1(4), Li1 N1A 373.7(4); O1-C1-N1-C2  58.4(2), O1- C1-N1-C3 63.8(2), C4-C1-N1-C2 65.3(2), C10-C1-N1-C3  60.8(2). In the dimeric structure the Li atoms Li1 and Li1A are bound to the anionic O atoms O1 and O1A and to the O atom of a THF molecule (O2 and O2A, respectively), leading to three-coordinate Li cations, which is rarely observed. The C1 O1 bond is 137.1(2) pm long, which corresponds to the C  O bond length in an a-alkoxyamine (137 pm). [6] In (CH 3 ) 3 C OLi a length of 139.2 pm has been determined for [11] a) G. Ashkenasy, C. E. Felder and A. Shanzer unpublished results; minimum-energy conformational studies, using EFF parameters, [11b] have been calculated and successfully compared with the NMR results; b) A. Shanzer, J. Libman, S. Lifson, C. E. Felder, J. Am. Chem. Soc. 1986, 108, 7609 ± 7619. [12] Y. Golan, L. Margulis, S. Maltis, I. Rubinstein, J. Electrochem. Soc. 1995, 142, 1629 ± 1633. [13] [Fe III (TPP)] ± imidazole complexation can be achieved either intra- molecularly to form 1:1 complexes, or intermolecularly to form a lateral array. In both arrangements the porphyrin ring would be oriented perpendicular to the surface. [14] Theoretic monolayer thicknesses were calculated from a model where the complexes or free ligands are oriented perpendicularly with respect to the surface. [15] The coverage of monolayers of 1, 2, and their complexes was measured by Cu UPD [4a] (UPD  underpotential metal deposition) as 77 ± 85 %. The exposed surface is attributed to the relatively large space between the bound disulfides. [16] G. A. Tondreau, D. A. Sweigart, Inorg. Chem. 1984, 23, 1060 ± 1065. [17] Prolonged rinsing in pure ethanol was ineffective, while the use of pure water caused the gold layer to exfoliate from the silicon surface. [18] G. Kalyuzhny, A. Vaskevich, G. Ashkenasy, A. Shanzer, I. Rubinstein, unpublished results. [19] P. OBrien, D. A. Sweigart, Inorg. Chem. 1985, 24, 1405 ± 1409. [20] Gold exposed to a [Fe III (TPP)Cl] solution under the same conditions showed no voltammetric peak or a very weak peak > 100 mV negative of that of the complex monolayer, which is attributed to physisorbed porphyrins. [*] Prof. Dr. G. Boche, Dipl.-Chem. M. Adler, M. Marsch Fachbereich Chemie der Universität D-35032 Marburg (Germany) Fax: ( 49) 6421 288917 E-mail : boche@ps1515.chemie.uni-marburg.de Prof. Dr. N. S. Nudelman Departamento Quimica Organica, Universidad de Buenos Aires Buenos Aires (Argentina) [**] This work was supported by the Deutsche Forschungsgemeinschaft (SFB 260) and the Fonds der Chemischen Industrie.