Distortion Coordinate for Five-Coordinated Tin. A Model for Nucleophilic Substitution. Synthesis and Structure of Hypervalent Anionic (Cyanoethylenedithiolato)stannates

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Reactions of Ph3SnCl and RSnCl3 (R = Me, n-Bu) with R4 N+Cl− and disodium maleonitriledithiolate, Na2(mnt), yield the monostannole [((CN)2C2S2)SnPh3][Me4N] (1) and the new distannoles [((CN)2C2S2)2,SnR][Et4N] [R = Me (2), n-Bu (3)]. X-ray analysis reveals the geometries of 1 as trigonal bipyramidal and 2 and 3 as square pyramidal. The tristannole [((CN)2C2S2)3Sn][Et4N][Na] (4) results from Sn-C bond cleavage of PhSnCl3 in a hydrolysis reaction with Na2(mnt) and Et4N+ Cl−. The geometrical data on organotin complexes containing ring unsaturation, 1-3, and related anionic five-coordinated tin compounds show that the distortion coordinate expressing solid-state nonrigidity is the Berry pseudorotational coordinate. As a result of this work, one is able for the first time to compare structural principles for five-coordinated compounds established for other main-group 14 and 15 elements. Their significance in reaction mechanisms is discussed. Stannole 1 crystallizes in the monoclinic space group Cc with a = 16.780 (3) Å, b = 9.433 (2) Å, c = 16.858 (3) Å, β = 96.85 (1)°, and Z = 4. Distannole 2 crystallizes in the monoclinic space group P21 /c with a = 14.997 (3) Å, b = 11.730 (3) Å, c = 14.167 (3) Å, e = 107.61 (2)°, and Z = 4. Distannole 3 crystallizes in the monoclinic space group P21 /m with a = 9.016 (2) Å, b = 10.906 (3) Å, c = 14.310 (2) Å, β = 98.35 (1)°, and Z = 2. Tristannole 4 crystallizes in the monoclinic space group C2/c with a = 9.434 (2)Å, b = 25.123 (6) Å, c = 12.773 (1) Å, β = 101.76 (1)°, and Z = 4. The final conventional unweighted agreement factors were 0.024 (1), 0.041 (2), 0.038 (3), and 0.035 (4).