From reactions between di(alkynyl)mercurials and lanthanoid elements in tetrahydrofuran or 1,2-dimethoxyethane, the organolanthanoids (PhCC)2Yb and (PhCC)2Eu(thf)0.25 (thf = tetrahydrofuran) have been isolated, and (RCC)2M (R = Ph or But, M = Yb; R = Ph, M = Eu) characterized in solution. Bis(phenylethynyl)ytterbium has also been obtained by ligand exchange between (C6F5)2Yb or (ButCC)2Y and phenylacetylene. The di(alkynyl)lanthanoids are considered to have associated structures with bridging alkynyl groups. Hydrolysis of (RCC)2M derivatives yields acetylenes RCCH, together with alkenes RCHCH2 (greater for M = Yb than M = Eu), and, when M = Yb, R = Ph, a little ethylbenzene.

Cyclopentadienyllanthanoids (C5H5)3M(thf) (M = Ce, Nd, Sm, Gd or Er; thf = tetrahydrofuran), (C5H5)3M (M = Er or Yb), (MeC5H4),M (M = Nd, Sm or Gd), (C5H5)2Yb, (C5H5)2Yb(dme) (dme = 1,2-dimethoxyethane), and (MeC5H4)2Yb(thf), have been synthesized in satisfactory-to-good yield by reaction of the lanthanoid elements with the thallous cyclopentadienides (RC5H4)TI (R = H or Me) in tetrahydrofuran or 1,2-dimethoxyethane. The outcome of the reaction of ytterbium with thallous cyclopentadienide [(C5H5),Yb; n = 2 or 3] depends on the stoichiometry; it has been shown that (C5H5),Yb is reduced by ytterbium metal to (C5H5),Yb and that the divalent compound is oxidized to (C5H5),Yb by thallous cyclopentadienide. Addition of mercury metal aids initiation of transmetallation, but it is not essential for reaction to occur.

From reactions of bis(polyfluorophenyl)ytterbium compounds R2Yb (R = C6Fs or p-HC6F4) with trans-Rh(CO)Cl(PPh3)2, NiCl2(bpy) (bpy = 2,2'-bipyridyl), NiCl2(PPh3)2, PtCl2(bpy)2 triphenyltin chloride, iodine and mercuric chloride, the polyfluorophenyl derivatives trans-RRh(CO)(PPh3)2, R2Ni(bpy), trans-(C6F5)2Ni(PPh3)2, (C6F5)2,Pt(bpy), Ph3SnC6Fs, C6F5I and (C6FS)2,Hg have been obtained. Reduction to mercury metal accompanied formation of the last compound. Carbonation of (C6F5)2Yb in tetrahydrofuran followed by acidification yields pentafluorobenzoic acid and, surprisingly, a significant amount of 2,3,4,5-tetrafluorobenzoic acid, in which the aromatic hydrogen is substantially derived from tetrahydrofuran. Reaction of (C6F5)2Yb with pentafluorobenzoic acid followed by acidification also gives 2,3,4,5-tetrafluorobenzoic acid. Fluoride elimination is less extensive and less specific in a similar reaction of YbI2.

The complexes, (C5H5)3M(py) (M = Nd, Sm, Eu or Yb), (C5H5)2Eu(py), and (C5H5)2Yb@y)2 have been prepared from the appropriate lanthanoid elements and thallous cyclopentadienide in pyridine, and (C5H5)3M(NCMe) (M = Nd, Sm or Yb) and (C5H5)2Yb(NCMe) from similar reactions in acetonitrile. Ligand exchange or addition has also been used to give (C5H5)3Sm(py), (C5H5)2Yb(py)2 and (C5H5)2Yb(NCMe). Ytterbium metal reduces (C5H5)3Yb(py) in pyridine to (C5H5)2Yb(py)2, which is oxidized back to (C5H5)3Yb(py) by T1(C5H5). Europium with (C5H5)2Hg in tetrahydrofuran yields (C5H5)3Eu(thf), and (C5H5)2Eu is not isolated by using an excess of metal. Oxidation of (C5H5)2Eu to (C5H5)3Eu is effected by (C5H5)2Hg in tetrahydrofuran but not by T1(C5H5) in 1,2-dimethoxyethane. Europium and ytterbium react with bis(pentafluoropheny1)mercury and cyclopentadiene in pyridine to give (C5H5)3M(py) (M = Eu or Yb).

In this paper, we consider a stochastic SIRS model with general incidence rate and perturbed by both white noise and color noise. We determine the threshold λ that is used to classify the extinction and permanence of the disease. In particular, λ < 0 implies that the disease-free (K, 0, 0) is globally asymptotic stable, i.e., the disease will eventually disappear. If λ > 0 the epidemic is strongly stochastically permanent. Our result is considered as a significant generalization and improvement over the results in [10,11,16,20,21].