COPPER(I) TETRAHYDROBORATE DERIVATIVES CONTAINING PHOSPHINE AND PHENANTHROLINE LIGANDS - AN ELECTROSPRAY MASS-SPECTROMETRIC STUDY OF SPECIES IN SOLUTION

Citation
R. Colton et al., COPPER(I) TETRAHYDROBORATE DERIVATIVES CONTAINING PHOSPHINE AND PHENANTHROLINE LIGANDS - AN ELECTROSPRAY MASS-SPECTROMETRIC STUDY OF SPECIES IN SOLUTION, Inorganic chemistry, 32(12), 1993, pp. 2626-2629
Citations number
17
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
ISSN journal
00201669
Volume
32
Issue
12
Year of publication
1993
Pages
2626 - 2629
Database
ISI
SICI code
0020-1669(1993)32:12<2626:CTDCPA>2.0.ZU;2-U
Abstract
Electrospray mass spectra have been obtained from dichloromethane/meth anol for cationic species existing in solutions of copper(I) tetrahydr oborate derivatives containing phosphine- and phenanthroline-type liga nds. Complexes of the type (L-L)Cu(PPh3)(BH4) (L-L = phenanthroline li gand) exist in solution as cationic [(L-L)Cu(PPh3)]+ species which are easily observed by electrospray mass spectrometry (ESMS). The triphen ylpbosphine ligand is labile and readily exchanges with excess triphen ylphosphine, or another monodentate phosphine, at rates which are mode rately fast on the P-31 NMR time scale at room temperature. However, u nder these conditions the [(L-L)-Cu(PPh3)2]+ cation can be observed by ESMS. When two different phosphines are present, two[(L-L)Cu(PR3)]+ i ons and all three possible [(L-L)Cu(PR3)2]+ cations are observed. Thus ESMS can observe individual cations from a solution in which the spec ies are rapidly exchanging. Tandem MS/MS spectra show that the [(L-L)C u(PR3)]+ cations readily lose phosphine and the [(L-L)Cu(PR3)2]+ catio ns are very unstable in the gas phase toward loss of phosphine. Reacti on of (L-L)Cu(PR3)(BH4) With 1 mol of L-L gives [(L-L)2Cu]+ ions which are observed in the ES mass spectrum. Interaction of[(L-L)2Cu]+ and a different phenanthroline complex [(L'-L')2Cu]+, or interaction of [(L -L)2Cu]+ With free L'-L', gives all three possible bis(phenanthroline) copper cations, thus demonstrating that the phenanthroline ligands are also labile. The compound (PPh3)2Cu(BH4) exists in solution as cation ic [Cu-(PPh3)2]+, which is also observable by ESMS. Addition of excess PPh3 gives fast ligand exchange (NMR), but ESMS shows the presence of both [Cu(PPh3)2]+ and [Cu(PPh3)3]+ ions. Addition of 2 mol of another phosphine (PR3) to [Cu(PPh3)2]+ also gives sharp averaged P-31 NMR si gnals for each phosphine at room temperature, but the ES mass spectrum shows peaks corresponding to all the bis(phosphine) and tris(phosphin e) cations. When 2 mol of each of two different phosphines are added t o 1 mol of [Cu(PPh3)2]+, the ES mass spectrum gives peaks for every po ssible combination of bis(phosphine)- and tris(phosphine)copper cation s.