Preparation of Dimolybdenum Cations with Triply Bridged Cores [Mo₂(μ-F)₂(μ-X)(CO)₄(PPh₃)₄]+ (X  F, Cl, Br, OH), [Mo₂(μ-Br)n(μ-OH)₃−n(CO)₄(PPh₃)₄]+ (n = 1, 2) and Ditungsten Cations [W(μ-F)n(μ-Br)₃−n (CO)₄(PPh₃)₄]+ Crystal Structure of [Mo₂(μ-Br)(μ-F)2(CO)₄(PPh₃)₄]F

Abstract

Title full: Preparation of dimolybdenum cations with triply bridged cores [Mo2(μ-F)2(μ-X)(CO)4(PPh3)4]+ (X F, Cl, Br, OH), [Mo2(μ-Br)n(μ-OH)3-n(CO)4(PPh3)4]+ (n = 1, 2) and ditungsten cations [W(μ-F)n(μ-Br)3-n (CO)4(PPh3)4]+ crystal structure of [Mo2(μ-Br)(μ-F)2(CO)4(PPh3)4]F. The reaction of Mo2Br2(CO)2(PPh3)2 with aqueous NaBF4 in CH2Cl2 leads to [Mo2(μ-X)(μ-F)2(CO)4(PPh3)4]+ (X Br, F, Cl, OH). The initially formed bromide can be isolated under appropriate conditions and crystallographically characterized as the unusual fluroide salt [Mo2(μ-Br)(μ-F)2(CO)4(PPh3)4]F (x hexane). The molecular unit is a triply bridged dimer with very long MoBr distances [2.694(3) and 2.693(3) Å], which are accounted for by the trans-influence of two nearly co-linear CO ligands (BrMOCO ca 165°). The bromide is fluxional, MoBr cleavage processes are evident from the variable temperature 31P NMR spectra. Under the reaction conditions the bromide is expelled leading to the formation of [Mo2(μ-X(μ-F)2(CO)4(PPh3)4]+ (X F, Cl, OH). Under identical conditions WBr2(CO)2(PPh3)2 reacts to form [W(μ-F)n(μ-Br)3-n(CO)4(PPh3)4]+ (n = 1,2) while reaction of Mo2Br2(CO)2(PPh3)2 with aqueous KPF6 leads to the hydroxo bridged dimers [Mo2(μ-Br)n(μ-OH)3-n(CO)4(PPh3)4]+ (n = 1,2). © 1994.

Department(s)

Chemistry

International Standard Serial Number (ISSN)

0277-5387

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1994 Elsevier, All rights reserved.

Publication Date

01 Jan 1994

Link to Full Text

Share

 
COinS