Synthesis, crystal structures and spectroscopic properties of dichloroethylphenyltin(IV) and its phenanthroline adduct

Synthesis and reactivity of β-stannylated phenylalanines

The free radical hydrostannation of a series of N-benzoyl and N-acetyl dehydrophenylalanine esters 2a – h yields β-stannylated phenylalanine derivatives 3 and 4. This addition of tin hydride to such unsaturated compounds simultaneously creates two new chiral centers leading to mixtures of two diastereomeric pairs of enantiomers. The reaction of 3-stannylated phenylalanine 3 with methanolic HCl yields chlorostannyl-substituted compounds 5 and 6 and, with one equivalent of bromine, the bromostannylated compounds 7 and 8 are formed. The bromostannylated phenylalanine derivative 7 reacts with one further equivalent of bromine to produce the dibromostannylated compound 9. Even the chlorostannylated phenylalanine derivative 5 reacts with one further equivalent of HCl to give the dichlorostannylated compound 10. The products were characterized by elemental analysis, infrared (IR), and multinuclear (1H, 13C, 119Sn) nuclear magnetic resonance (NMR) spectroscopy. Attempts were made to assign the preferred conformation of the stannylated phenylalanine derivatives using Karplus-type relationship of coupling constants 3 J(H,H), 3 J(Sn,H), and 3 J(Sn,C=O). The results of these analyses have been confirmed by three crystal structure determinations.

Dibromodiphenylstannane: isolated centrosymmetric dimers as a new structure motif for the intermolecular association of diorganotin(IV) dihalides

In the crystalline state, the low-melting title compound [common name: diphenyltin(IV) dibromide], [SnBr(2)(C(6)H(5))(2)], consists of distorted tetrahedral molecules with compressed halide and enlarged carbon opening angles of 102.741 (9) and 123.53 (8)°, respectively, and Sn-C and Sn-Br bond lengths of 2.109 (2)/2.113 (2) and 2.4710 (3)/2.4947 (3) Å, respectively. Intermolecular Sn...Br interactions, typical for diorganotin(IV) dihalides, R(2)SnHal(2) (with Hal = Cl, Br, I), and sterically less demanding organic groups lead to the formation of a hitherto unknown association pattern consisting of centrosymmetric dimers with an antiparallel orientation of the dipole moments and two weak intermolecular Sn...Br distances of 3.8482 (3) Å between one of the two Br atoms and its neighbouring Sn atom, and vice versa. The second Br atom is not involved in intermolecular interactions and lies somewhat outside the association plane that, therefore, is not coplanar [interplanar angle = 1.750 (2)°] with the tin-halide plane. The new structure motif of intermolecular tin-halide interaction can be classified as 2a(i), which indicates the number of molecules (i.e. '2') composing the oligomer, the antiparallel orientation (i.e. 'a') of their dipole moments and the centre of symmetry (i.e. 'i') giving rise to the association pattern.