Synthesis, Characterization, and Hydrolytic Behavior of Mixed-Ligand Diorganotin Esters, [R₂Sn(O₂CR‘)OSO₂Me]₂ (R = n-Pr, n-Bu; R‘ = C₉H₆N-2, 4-OMe-C₉H₅N-2, C₉H₆N-1)

Reactions of the tin precursors, R2Sn(OMe)OSO2Me (R = n-Pr, n-Bu), with an equimolar quantity of 2-quinoline/4-methoxy-2-quinoline/1-isoquinoline carboxylic acid in acetonitrile proceed under mild conditions (rt,12−15 h) via selective Sn−OMe bond cleavage to afford the corresponding mixed-ligand diorganotin derivatives [R2Sn(O2CR‘)OSO2Me]2 [R‘ = C9H6N-2, R = n-Pr (1), n-Bu (2); R‘ = 4-OMe-C9H5N-2, R = n-Pr (3), n-Bu (4); R‘ = C9H6N-1, R = n-Pr (5), n-Bu (6)]. These have been characterized by FAB mass, IR, and multinuclear (1H, 13C, 119Sn) NMR spectral data and X-ray crystallography (for 4 and 6). The molecular structure of 4 (C20H29NO6SSn, monoclinic, P21/n, a = 14.1(13) Å, b = 16.7(18) Å, c = 20.3(19) Å, β = 107(4)°, Z = 8) comprises distorted octahedral geometry around each tin atom by virtue of weakly bridging methanesulfonate [Sn(1A)−O(3B) = 3.010, Sn(1B)−O(3A) = 2.984 Å] and {N,O} chelation of the carboxylate ligands. The spectral data of 1−4 suggest a similar structural motif in solution. The molecular structure of 6 (C38H53N2O10S2Sn2, monoclinic, P21/c, a = 11.339(2) Å, b = 14.806(3) Å, c = 24.929(5) Å, β = 100.537(3)°, Z = 4) reveals varying bonding preferences with monomeric units being held together by a bridging methanesulfonate [Sn(2)−O(5) = 2.312(2) Å] and a carboxylate group bonded to Sn(1) and Sn(2) atoms, respectively. Slow hydrolysis of compound 2 derived from 2-quinoline carboxylic acid in moist CH3CN affords the asymmetric distannoxane, [Bu2Sn(O2CC9H6N-2)-O-Sn(OSO2Me)Bu2]2 (7) (C27H45NO6SSn2, monoclinic, C2/c, a = 21.152(3) Å, b = 13.307(2) Å, c = 26.060(4) Å, β = 110.02(10)°, Z = 8) featuring ladder type structural motif by virtue of unique μ2-coordination of covalently bonded oxygen atoms [O(6), O(6)#1] of the methanesulfonate groups.