TRIPLY BRIDGED BINUCLEAR THIOLATE COMPLEXES OF OXOMOLYBDENUM(V) - SYNTHESIS OF [MO2O2(SR)6Z]-(Z=OR',SR',NR'2) AND CRYSTAL-STRUCTURES OF (ET4N)[MO2O2(SCH2CH2O)2CL3] (ET4N)[MO2O2(SCH2CH2O)3CL] AND (PR3NH)[MO2O2(SCH2CH2O)3(SCH2CH2OH)]

The reactions of various mononuclear oxomolybdenum(V) complexes with thiolate ligands have been studied and shown to produce triply bridged binuclear complexes. Three homologous diamagnetic complexes, (Et4N)[Mo2O2(SCH2CH2O)2Cl3], (Et4N)[Mo2O2(SCH2CH2O)3Cl], and (Pr3NH)[Mo2O2(SCH2CH2O)3(SCH2CH2OH)] have been isolated. Crystal structures determined for these three compounds reveal the common occurrence of a molecular structure containing a triply bridged pair of MoO units: the three monoanionic complexes differ in chloride/2-oxoethanethiolate substitution at nonbridging coordination sites. The triple bridge is formed by the sulfur (cis to both 0=Mo bonds, mean Mo—S = 2.48 Å) and oxygen (approximately trans to both 0═Mo bonds, mean Mo—O = 2.18 Å) atoms of one -SCH2CH20- ligand and the oxygen atom (cis to both O═Mo bonds, mean Mo—O = 2.03 Å) of a second -SCH2CH20- ligand which also chelates one molybdenum atom. Asymmetric six-coordination occurs for both molybdenum atoms. The binuclear complex is regarded as two square-pyramidal Mo═0 units which share one edge of their basal coordination planes and also share one more weakly bound atom approximately trans to both Mo═0 bonds. Mean Mo-Mo = 2.73 Å. The reaction between MoOCl3(THF)2 and alkylthiols in the presence of base in MeCN or DMF leads to the anions [Mo2O2(SR)7]-, of which the salts B[Mo2O2(SR)7] with quaternary cations have been isolated in substance. The mononuclear arylthiolato anions [MoO(SAr)4]- (Ar = Ph, p-tolyl) react in the presence of a source of alkoxy or amido ligand, Z, to form related B[Mo2O2(SAr)6Z] salts. Such reactions are promoted by the oxidation of 1 mol of -SAr ligand by FeCl3. Physical data indicate that these binuclear monoanions are also triply bridged species containing thiolate and Z bridging ligands. Structural and chemical implications of the stereochemistry of the triple bridge are discussed. Crystal data: (Et4N)[Mo2O2(SCH2CH2O)2Cl3], a = 12.877 (1) Å, b = 15.351 (1) Å, c = 13.147 (1) Å, 0 = 122.76 (1)°, P2,/c, Z = 4; (Et4N)[Mo2O2(SCH2CH2O)3Cl], a = 15.387 (1) Å,b = 10.928 (1) Å, c = 14.062 (1) Å, Pnalx, Z = 4; (Pr3NH)[Mo2O2(SCH2CH2O)3(SCH2CH2OH)], a = 9.696 (1) Å, b = 10.800 (1) Å, c = 14.401 (1) Å, a = 86.37 (1)°, P = 88.01 (1)°, y = 65.00 (1)°, PI, Z = 2. © 1979, American Chemical Society. All rights reserved.