Synthesis, characterisation and crystal structures of asymmetric (Z)-1-[2-(triphenylstannyl)vinyl]-1-indanol and its diphenylbromostannyl derivative

Abstract

Recently, the synthesis and antitumour activity of organotin compounds of the type (Z)-CH 2 (CH 2 ) n C(OH)CH=CHSnAr 3 (Ar = phenyl and p-tolyl; n = 3, 4 and 5), with intramolecular O→Sn coordination have been actively studied. In particular, the effects of the symmetric 1-vinyl-1-hydroxy [CH 2 (CH 2 ) n (HO)CCH=CH-] alkyl groups on both the structure and the antitumour activity of this type of compound have been extensively reported. [1][2][3][4] To the best of our knowledge, asymmetric (at C-1) 1-vinyl-1-hydroxy alkyl group-substituted organotin compounds have not yet been reported. We report here the synthesis and structure of asymmetric (Z)-1-[2-(triphenylstannyl)vinyl]-1-indanol 1 and (Z)-1-[2-(bromodiphenylstannyl)vinyl]-1-indanol 2. Their structural features, particularly the HO→Sn coordination interaction, are discussed. These compounds are likely to serve as new models for further investigations of structure-antitumour activity relationships.The compounds 1 and 2 were synthesised according to Scheme 1. The indanol 1 was prepared by the addition of triphenyltin hydride to the triple bond of 1-ethynylindanol and the reaction of 1 with bromine in a 1:1 molar ratio yielded 2.The molecular structures of 1 and 2 are given in Figs 1 and 2 and selected distances and bond angles are listed in Table 1. The Sn atom in 1, bonded to three phenyl groups and the C(19) atom of the vinyl residue, adopts a distorted tetrahedral geometry, with C-Sn(1)-C angles ranging from 101.9(3) to 117.5(3)°. The C(7)-Sn(1)-C( 19) angle [117.5(3)°] is significantly larger than the other C-Sn(1)-C angles due to weak coordination of the O(1) atom of the indanol hydroxyl group. The distance between the O(1) and the Sn(1) atoms is 2.778(8) Å, which is significantly less than the sum of their van der Waals radii [3.70 Å]. 5 The weak coordination of the O(1) atom also influences the strength of the Sn(1)-C(phenyl) bond and as a result 6 , the Sn(1)-C(1) is longer by 0.02 Å than the other two Sn-C(phenyl) bonds. The fact that the Z isomer rather than the E isomer was obtained from this type of reaction may be attributed to the weak intramolecular O→Sn coordination. 2,4 The Sn atom in 2 is five coordinate and the molecule has a distorted trigonal bipyramidal geometry with the trigonal plane defined by the C(1), C(11) and C(21) atoms and the axial positions occupied by the Br(1) and O(1) atoms. This is similar to the reported analogue (Z)-1-[2-(chlorodi-ptolylstannyl)vinyl]-1-cycloheptanol. 2 The Sn(1)•••O(1) distance of 2.375(6) Å is in the range of a normal Sn-O coordination bond length, 2,3,4 indicating that the Sn atom in 2 is formally coordinated by the O(1) atom of the hydroxyl group and that the Lewis acidity of the Sn atom in the (phenyl) 2 SnBr moiety is greater than that in the (phenyl) 3 Sn moiety. On the other hand, the O(1)-C( 31) bond (1.456(10) Å) in 2 is weaker than the corresponding bond (1.435(8) Å) in 1 due to the strong coordination interaction between the O(1)