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