G.K. Sandhu

Diorganotin(IV) derivatives of N-phthaloyl amino acids

Twentyfour complexes of the general formulae (R2SnL2 and R2(L)SnOSn(L)R2 (L = N-phthaloyl derivative of l-leucine, dl-alanine and l-phenylalanine; R = CH3, C5H5, n-C4H9) and n-C8H17) have been prepared by reacting ligand and dialkyltin(IV) oxide in 2/1 and 1/1 (ligand/metal) molar ratio. These complexes have been characterised by elemental analysis and structures assigned with the help of infrared, 1H NMR and 119Sn Mossbauer spectroscopy. These data support six-coordinated distorted octahedral structures with two alkyl groups in trans positions.

Diorganotin(VI) complexes of N-acetylamino acids

Abstract Sixteen complexes of general formula R2SnL2 and R2(L)SnOSn(L)R2 (where L = N-acetyl-L-leucine or N-acetyl-L-phenylalanine) R = CH3, C2H5, n-C4H9, or n-C8H17) have been prepared by interaction between the ligand and R2SnO in 2:1 or 1:1 molar ratio. The complexes were characterized by IR, 1H NMR and 119Sn Mossbauer spectroscopy. All the 2:1 complexes are assigned six-coordinate, distorted octahedral geometry with chelating carboxylate groups, while the 1:1 complexes have oxygen-bridged binuclear five-coordinate, trigonal-bipyramidal configurations. The amido −CO and −NH groups are hydrogen bonded in the solid state.

Triorganotin(IV) derivatives of five membered heterocyclic 2-carboxylic acids

Abstract A series of 20 complexes of general formula R3SnL (R = CH3, n-C3H7, n-C4H9, C6H5, c-C6H11 ; L = anion of thiophene 2-, thiophene 2-acetic, furoic 2- and pyrrole 2- carboxylic acids) has been prepared. All of these complexes are monomers except those of triphenyltin(IV) which are polymers and have been characterised by molecular weight determination, IR, 1H-NMR and 119mSn Mossbauer studies. Tetrahedral and trigonal bipyramidal structures have been assigned and it has been found that none of the ring hetero atoms bond to tin(IV).

Structural chemistry of organotin carboxylates: XIV. Diorganotin(IV) complexes of monochloroacetyl-lphenylalanine. Crystal structure of [nBu2Sn(O2C(CH2Ph)C(H)N(H)C(O)CH2Cl2)2]

Abstract New diorganotin(IV) complexes of the general formulae [R 2 Sn(A) 2 ] and {[R 2 Sn(A)] 2 O} ( = the anion of monochloroacetyl- l -phenylalanine and R = Me, n Pr, n Bu and n Oct) have been prepared and characterized by 1R and 1 H NMR spectroscopy and, in the case of the [ n Bu 2 Sn(A) 2 ] compound, by X-ray crystallographic metods. The 1:2 (Sn:ligand) compounds are monomeric, and the Sn atom has a skew trapezoidal planar geometry, whereas the 1:1 compounds are dimeric with SnOSn bridges and possess trigonal bipyramidal Sn atom geometries.

Structural chemistry of organotin carboxylates. VIII, Synthesis and spectroscopic properties of diorganotin(IV) complexes with thiophenoxyacetic acid. X-ray crystal structures of [nPr2Sn(O2CCH2SPh)2] and {[R2Sn(O2CCH2SPh)]2O}2, R = nPr, nBu

Abstract Two types of diorganotin(IV) complexes i.e.[R 2 Sn(O 2 CCH 2 SPh) 2 ] ( 1–5 ) and {[R 2 Sn(O 2 CCH 2 SPh) 2 -O} 2 ( 6– ), R = Me, Et, n Pr, n Bu and n Oct, have been prepared in 1:2 and 1:1 molar ratios (tin:ligand) by reacting diorganotin oxide with thiophenoxyacetic acid. Characterization of the complexes was achieved using IR and 1 H NMR spectroscopy and in the case of the n Pr and n Bu complexes, by X-ray diffraction methods. The 1:2 compounds are monomeric with the Sn atoms existing in skew-trapezoidal planar geometries with assymetrically coordinating carboxylate ligands and C−Sn−C angles of 136.7(2) and 140.7(2)° respectively. The 1:1 compounds adopt the familiar dicarboxylato tetraorganodistannoxane structural mode. The structures feature two bidentate bridging and two monodentate carboxylate ligands, and both Sn atoms in the centrosymmetric dimers are in distorted trigonal bipyramidal geometries.

Preparation, infrared and 13C and 119Sn NMR spectral studies of triorganotin(IV) derivatives of N-acetyl-l-phenylalanine and N-acetyl-l-phenylalanylglycine

Abstract Triorganotin(IV) derivatives of N-acetyl- l -phenylalanine (HAA) and N-acetyl- l -phenylalanylglycine (HDP), R3SnAA and R3SnDP (where R = methyl, n-propyl, n-butyl, phenyl and cyclohexyl, respectively), have been prepared from triorganotin(IV) chlorides (R3SnCl) and the sodium salt of the appropriate N-acetylamino acids. All the compounds in the solid state have a polymeric structure with a unidentate carboxylic group. The molecules are linked together via the weak intermolecular donoracceptor bond NHCO …Sn(R3O. The fragment of O…Sn(R3)O has slightly deformed trans-trigonal bipyramidal geometry around the central tin atom. In chloroform solution, all the compounds are present in the form of simple molecules with a nearly tetrahedral configuration of the R3SnOCO group.

Structural chemistry of organotin carboxylates. V, X-ray crystal structure of polymeric trimethylstannyl thiophene-2-carboxylate

Abstract The crystal structure of the title compound, [Me 3 Sn(O 2 CC 4 H 3 S)] n , has been determined at 205 K. The structure features bidentate bridging thiophene-2-carboxylate ligands and five-coordinate Sn atoms, and represents an additional example of the trans -R 3 SnO 2 structural type found for related systems.

Structural chemistry of organotin carboxylates: XVII. Diorganotin(IV) derivatives of N-phthaloyl-dl-valine

New diorganotin(IV) complexes of the general formula [R2Sn(A)2] and {[R2Sn(A)]2O}2 (where A is the anion derived from the N-phthaloyl derivative of dl-valine and R  Me, nBu and nOct) have been prepared and characterized by spectroscopic methods and in the case of the {[Me2Sn(A)]2O}2 compound, by X-ray crystallographic methods. The Sn atoms in the [R2Sn(A)2] complexes are six-coordinate and the {[R2Sn(A)]2O}2 complexes are examples of dicarboxylato tetraorganodistannoxanes. The crystal structure of {[Me2Sn(A)]2O}2 shows both the endocyclic and exocyclic Sn atoms to be five-coordinate, trigonal bipyramidal. Several weak intramolecular contacts are noted with the most noteworthy being a contact of 3.15(1) A between the imido CO atom and the endocyclic Sn atom.

Structural chemistry of organotin carboxylates: I. The crystal structure of di-n-butylbis(thiophenoxyacetato)tin(IV): nBu2Sn(O2CCH2SC6H5)2

Abstract A crystal structure study of n Bu 2 Sn(O 2 CCH 2 SC 6 H 5 ) 2 reveals the compound to be monomeric with the tin atom situated on a crystallographic 2-fold axis in a skew-trapezoidal bipyramidal geometry. The basal plane is defined by two asymmetrically chelating carboxylate groups; SnO 2.134(4) and 2.559(5) A and the n BuSn n Bu angle is 140.7(2)°. The sulphur atoms do not participate in any significant interactions to the tin atom. Crystals are monoclinic with space group C 2 and unit cell dimensions a 18.668(6), b 15.761(6), c 5.106(5) A, β 117.55(5)°; Z = 2. The structure was refined by a full-matrix least-squares procedure to final R = 0.034 and R w = 0.033 for 1294 reflections with I ≥ 2.5σ( I ).

Diorganotin(IV) complexes of N-protected dipeptides

Abstract Eight new diorganotin(IV) complexes of general formula R 2 Sn(DP) 2 and [R 2 Sn(DP)] 2 O (DP = anion of N -benzoyl- dl -alanylglycine; R = CH 3 , C 2 H 5 , n-C 4 H 9 , n-C 8 H 17 ) have been prepared and characterised by IR, and 119m Sn Mossbauer spectroscopy. However, only two complexes, (DP) 2 Sn(n-C 4 H 9 ) 2 and (DP) 2 Sn(n-C 8 H 17 ) 2 were sufficiently soluble for NMR ( 1 H and 13 C) studies. The 2 : 1 complexes are monomeric with distorted trans -octahedral structures. The 1 : 1 complexes are dinuclear with Sn-O-Sn bridges and trigonal bipyramidal geometry about tin. In both cases the dipeptide acts as an O,O -bidentate ligand.