Organometallics 1994,13, 2849-2854
2849
Tri-n-butyltin2,6-Difluorobenzoate, a Unique Macrocyclic Tetramer Containing a 16-Membered Sn4C408 Ring, and Other Related Compounds Marcel Gielen,'*t Abdelaziz El Khloufi,? Monique Biesemans,tJ Franqois Kayser,+J and Rudolph WillemtJ Faculty of Applied Sciences, Laboratory for General and Organic Chemistry (AOSC), Room 8G512, and High Resolution NMR Centre, Free University of Brussels (V.U.B.), Pleinlaan 2, B-1050 Brussels, Belgium
Bernard Mahieu Catholic University of Louvain, INAN, B-1348 Louvain-la-Neuve, Belgium
Dominique Maes, John N. Lisgarten, and Lode Wyns Free University of Brussels (V.U.B.), Department of Ultrastructure, Institute of Molecular Biology, Paardenstraat 65, B-1640 Sint-Genesius Rode, Belgium
Alex Moreira, Tapan K. Chattopadhay, and Rex A. Palmer Department of Crystallography, Birkbeck College, University of London, Malet Street, London WClE?HX, UK Received January 25, 1994" The X-ray crystal structure determination of tri-n-butyltin 2,6-difluorobenzoate, compound 4, revealed the compound to exist as a macrocyclic tetramer with d symmetry. The five-coordinated tin atoms have distorted trigonal bipyramidal geometries with the three butyl groups occupying equatorial positions and the carboxylate ligands bridging the tin atoms as bidentate ligands in apical positions. Crystals of the compound 2,6-F&sH&OzSnBu3, M,= 447.12, are tetragonal, space group Id, with 2 = 8 in a unit cell of dimensions a = 15.631(3) A, c = 16.882(1) A with R = 0.037 for 3151 unique reflections. In the cyclotetramer, each tin atom exhibits one strong and one weak Sn-0 bond. The synthesis and spectral characterization of eight other related tri-n-butyltin carboxylates are presented. As for compound 4, its solution structure is monomeric, with a tetrahedral tin atom. Introduction A recent review by Tiekinkl reveals that, basically, triorganotin carboxylates belong to three classes of structure in the crystalline state: a, b, and c (see Figure 1). Structure class a is characterized by a four-coordinate distorted tetrahedral tin atom; a typical example of class a is triphenyltin salicylate,2in which the bonding oxygentin distance is 2.083(2) A and the nonbonding one, 3.071(2) A. In trimethyltin salicylate, however, tin is fivecoordinate as the trimethyltin moiety is bound to a monodentatecarboxylategroup as wellas to the o-hydroxyl group of a neighboring monomer unite3 Structure class b contains a five-coordinate tin atom with a bidentate carboxylate moiety. This geometry is based on a distorted trigonal bipyramid with the carboxylate oxygen atoms spanning one apical and one equatorial position. A typical example of class b is triphenyltin o-(dimethylamino)bemate,4in which the two bonding tin-oxygen dietances are 2.564(7)and 2.115(6)A,
R
R
Figure 1. Three structureclassesfor compoundsof the type R'COOSnR3.1
respectively. Both structures a and b are monomeric. It is interesting to note that triphenyltin o-aminoben~oate~ is characterized by a quite long coordination bond (2.823(3) A) as compared to that of the dimethylamino analog (2.564(7) A) due, in part, to the presence of an intramot Faculty of Applied Sciences, Free University of Brussels. lecular hydrogen bond between the carbonyl oxygen and t High Resolution N M R Centre, Free University of Brussels. the o-NH2 group. Abstract published in Advance ACS Abstracts, June 1,1994. Structure class c is polymeric, with bidentate carboxyl(1) Tiekink, E. R. T. Appl. Organomet. Chem. 1991,5, 1. (2) Vollano, J.F.; Day, R. 0.;Chandrasekhar, V.; Holmes, R. R. Inorg. ates bridging the five-coordinatetin atoms of the polymeric Chem. 1984,23, 3153. (3) Smith,P.J.;Day,R.O.;Chandrasekhar,V.;Holmes,J.M.;Holmes, chain. A typical example is triphenyltin acetate? in which
R. R.Inorg. Chem. 1986,25, 2496. (4) Swisher,R.G.;Vollano,J.F.;Chandresekhar,V.;Day,R.O.;Holmea, (5) Molloy,K. C.; Qua,K.; Nowell, I. W. J. Chem. SOC.Dalton Trans. R.R. Inorg. Chem. 1984,23, 3147. 1987, 101.
0276-733319412313-2849$04.50/0 0 1994 American Chemical Society
Gielen et al.
2850 Organometallics, Val. 13, No. 7, 1994 the two bonding tin-oxygen distances are 2.185(3) and 2.349(3) A. The 0-Sn-0 angle is 173.6(1)”. The crystal structure of only one tri-n-butyltin carboxylateof this clesa, tri-n-butyltinindole-3-acetate,Bhas so far been determined. Its coordination bond between the carbonyl oxygen and tin is 2.524(3) A, a distance significantlylonger than 2.199(3) A for the covalent 0-Sn bond, and the 0 S n - O angle is 173.5(2)’. The choice of structures in these systems is dictated718by both steric and electronic effects. This paper presents a structure type unreported up to now for triorganotin carboxylates. It consists of a macrocyclic tetramer. The physical characteristics of some other related compounds are likewise reported.
Table 1. Atomic Fractional Coordinates of Tri-mbutyltin z6-Twluombf?”te,compound 4
Results and Discussion Synthesis. The tri-n-butyltin compounds were synthesized by a 1:l condensation of tri-n-butyltin acetate with the appropriate substituted benzoic acids.D
-
XYZC,H2C02H + CH3C02SnBu3 XYZC,H2C02SnBu3 CH3COOH
+
1: X,Y,Z = 2-F, H, H 2: X,Y,Z = 2,3-F2, H 3: X,Y,Z = 2,5-F2, H 4 X,Y,Z = 2,6-F2, H 5: X,Y,Z = 3,5-F2, H 6: X,Y,Z = 3-CH.@,2-OH, H 7: X,Y,Z = 4-CH30, %OH,H 8: X,Y,Z = 5-CH,O,2-OH, H 9: X,Y,Z 6-(CH&CH, 3-CH3,2-0H
After having distilled offthe aceticacid generated,together with the solvent ethanolltoluene, the compounds were purified either by recrystalliition or by distillation under vacuum. Details are given in the Experimental Section. X-ray Diffraction Data and Structure of Tri-nbutyltin 2,6-Difluorobemzoate. The atomic fractional coordinates of tri-n-butyltin 2,6-difluorobenzoate, compound 4, are given in Table 1. The atom numbering is shown in ORTEP drawing, Figure 2, and the molecular structure of the macrocyclic tetramer 4, in Figure 3. Selected interatomic parameters are listed in Table 2. Compound 4 displays an unusual macrocyclic tetrameric structure. The cyclotetramerhas 3 symmetry. Operation (-x + of the transformations 01 + V 2 , -x + V 2 , -2 + 1,-y, z ) c , and (-y + ll2, x - lI2,-z + 3/2)d on the asymmetric unit (Figure 2) results in formation of the tetrameric unit (Figure 3). The contributing moieties are designated a(xyz), b, c, and d in Figure 3. The carboxylategroupsbridge two neighboringtin atoms such that the Sn-O bonds formed by the bridging ligands are asymmetric with values of 2.186(4) and 2.514(4) A, respectively (Table 2), as are the comparablebonds in the linear polymers of class c (seeFigure 1);the oxygen atoms occupy the apical positions of the trigonal bipyramidal tin atoms, with 0-Sn-0 angles of 175.2(1)O. The three (6) Molloy, K. C.; Purcell, T.0.; Mahon, M. F.;Mhhal.4 E. Appl. Orgummet. Chem. 1987,1, Mn. (7) Molloy, K.C.; Blunden, 5.J.; Hill,R.J. Chem. Soc. Dalton DUM. 1988,1259.
(8) Simons, P.B.; Graham,W. A. G. J. Orgonomet. Chem.1967,479. (9) Gielen, M.;Willem, R.;Biwmens, M.;Boulllam, M.;El Khloufi, A.;de Vos, D. Appl. Organornet. Chem. 1992,s. 287.
X
Y
0.35351(2) 0.4349(2) 0.5454(2) 0.57 17(3) 0.5613(3) 0.3554(4) 0.3677(5) 0.3640(5) 0.3721(5) 0.4265(4) 0.3940(4) 0.4093(6) 0.3813(8) 0.2454(4) 0.1864(4) 0.1064(4) 0.1229(8) 0.5119(3) 0.5640(3) 0.5896(4) 0.6327(5) 0.6498(5) 0.6274(4) 0.5852(4)
0.17839(2) 0.2875(3) 0.2318(3) 0.3078(3) 0.421 3(3) 0.1948(3) 0.2892(4) 0.3034(5) 0.3974(5) 0.0866(4) 0.0713(4) 0.1466(5) 0.13 13(7) 0.2341(4) 0.2855(4) 0.3176(5) 0.3813(9) 0.2869(3) 0.3622(3) 0.3726(4) 0.4426(5) 0.5080(5) O.SOlS(4) 0.4278(4)
z 0.71891 (2) 0.6890(2) 0.7535(2) 0.5562(2) 0.8110(3) 0.8437(3) 0.8684(4) 0.9564(4) 0.9776(5) 0.6538(4) 0.5711(4) 0.5 145(4) 0.4326(5) 0.6603(4) 0.7 127(5) 0.6694(5) 0.61 12(9) 0.7116(4) 0.6848(4) 0.6075(4) 0.5797(5) 0.6316(6) 0.7096(7) 0.7342(4)
Table 2. Selected Bond Lengths (A)and Angles (deg) in Comwund 4. Sn( I)
