ALKALI METAL DERIVATIVES OF GROUP IV ORGANOMETALLICS: MECHANISTIC ASPECTS OF REACTIONS WITH HALIDES
Organometallic derivatives of the Group IV elements have been known and used as synthetic intermediates for a half century, but little has been done by way of systematic investigation of the scope, and limitations of their reactions. And only recently have investigators turned their attentions to the study of mechanistic aspects of these reactions. An overview of the field reveals many highly useful facts, but it is also strewn with some contradictory observations, along with many others that are difficult to fit into a coherent overall conceptual scheme. This scheme lies beyond the present horizon and will be revealed only after completion of systematic studies on the various parameters affecting the scope, limitations, and mechanisms of these reactions. Delineation of these, in turn, will provide reliable guides to their synthetic utility. This report deals with our present understanding of the mechanisms of Group IV organometalalkalis with organic halides, with reference to other reactions as appropriate, and with some of the questions concerning these reactions, whose answers lie beyond the horizon. Experimental observations which are relevant for understanding of mechanisms will be first summarized; mechanisms consistent with these will be reviewed; and questions remaining to be answered will be raised. Because of the nature of the presently known facts, those concerning silicon, germanium, tin, and lead alkalis will be intermingled, and valid trends within the series will be indicated.
Investigations on organolead compounds VI. Triphenylplumbylsodium and triphenylplumbylmagnesium halide
Triphenylplumbylsodium can be prepared from hexaphenyldilead and finely divided sodium in tetrahydrofuran at room temperature while triphenylplumbylmagnesium halide can be conveniently prepared from lead dichloride and phenylmagnesium chloride or bromide in tetrahydrofuran. 
 
These reagents resemble the previously investigated compound triphenylplumbyllithium in many respects. They usually couple readily with reactive halides, but sometimes an exchange reaction is observed. The tendency to exchange increases in the order: Ph3PbNa< Ph3PbLi< Ph3PbMgX.
Neuronal uptake inhibitors, nisoxetine and fluoxetine on rat vascular contractions.
The importance of neuronal uptake processes in rat arteries and veins was compared using nisoxetine and fluoxetine, selective inhibitors for neuronal uptake of norepinephrine and serotonin, respectively. Nisoxetine (10(-7) - 10(-5) M) increased the sensitivity to exogenous norepinephrine in the portal and mesenteric veins (10-fold) and in the mesenteric artery (2.5-fold). Responses to field stimulation were also increased afternisoxetine in all three vessels. After nisoxetine, aortic responses to norepinephrine were unaltered and in all tissues, serotonin-induced contractions were reduced. Fluoxetine did not potentiate responses to norepinephrine or to field stimulation except in the mesenteric vein where sensitivity to norepinephrine was increased and the relaxation rate after field stimulation was prolonged. Although serotonin has been detected in blood vessels, fluoxetine did not increase vascular responses to serotonin. These studies suggest that rat mesenteric veins have a highly sensitive neuronal uptake mechanism of norepinephrine. Furthermore, these data provide indirect evidence against a functionally important serotonergic uptake process in rat blood vessels and suggest that neuronal uptake of serotonin does not exert a major role in terminating the vascular action of this biogenic amine.