CHEMISTRY OF ETA-2-CS2 METAL-COMPLEXES - COMPARISON OF THE REACTIVITIES OF THE 2 ISOMERIC HETEROMETALLACYCLES MOC(S)SC(R)=CR AND MOSC(S)C(R)=CR - UNEXPECTED FORMATION OF A CARBON CARBON BOND BETWEEN THE 5-MEMBERED METALLA RING AND AN ETA-5-CYCLOPENTADIENYL LIGAND

Two aspects of the chemistry of the two isomeric heterometallacycles arising from 1:1 addition of alkynes to [Cp2Mo(ƞ2-CS2)], i.e. [Cp2MoC(S)SC(R)═CR] (1a, R = CO2Me; 1b, R = CF3) and [Cp2MoSC(S)C-(R)═CR] (2a, R = CO2Me), have been studied: (i) their reactions with methyl iodide and (ii) the subsequent reactions with sodium tetrahydroborate. While CH3I reacts with la and 2a to give the corresponding S-methylated cationic complexes [Cp2MoC(SCH3)SC(R)═CR]I (3a, R = CO2Me) and [Cp2MoSC-(SCH3)C(R)═CR]I (4a, R = CO2Me), respectively, the reaction with 1b affords the molecular complex [CpMo(ƞ7-C5H4C(SCH3)SC(R)═CR)] (5b, R = CF3). Complex 3a reacts with sodium tetrahydroborate to give 5a, the CO2Me analogue of 5b, and [Cp2MoCH(SCH3)SC(R)═CR] (6a, R = CO2Me). Complex 4a reacts with sodium tetrahydroborate to afford [CpMo(ƞ7-C5H4C(R)C(R)═C(SCH3)S)] (7a, R = CO2Me) and [Cp2MoSCH2C(R)═CR] (8a, R = CO2Me). Possible mechanisms for these reactions are discussed. The structure of 5b has been determined by single-crystal X-ray diffraction analysis. The crystals are monoclinic, space group P21/c, with a = 11.861 (3) Å, b = 9.839 (3) Å, c = 15.075 (4) Å, β = 106.28 (2)°, V = 1688.7 (5) Å3, Z = 4 and Dc = 1.88 g·cm-3. The structure was solved by using 2953 unique reflections (I> 3σ(I)) and refined to R = 0.027 and RW = 0.024. This study clearly shows the unexpected formation of a carbon-carbon bond between a cyclopentadienyl group and the heterometallacyclic fragment (C-C = 1.454 (3) Å). © 1990, American Chemical Society. All rights reserved.