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.
Complications of motility peg placement for porous hydroxyapatite orbital implants
Aim: To evaluate the complications associated with pegging of porous hydroxyapatite orbital implants. Methods: Complications associated with pegging were retrospectively reviewed from the charts of 100 of 133 patients with hydroxyapatite implantation from 1993 to 2000. Results: 48 (48%) of the 100 hydroxyapatite implanted patients who had undergone pegging were found to have problems with their pegs, including discharge (45.8%), peg falling out (20.8%), pyogenic granulomas (16.7%), popping peg (14.6%), hydroxyapatite visible around peg hole (8.3%), part of peg shaft visible (6.2%), peg drilled off centre (6.2%), peg drilled at an angle (4.2%), and excess movement of peg (4.2%). The standard peg fell out statistically more often than the peg and sleeve system (Yates's corrected χ2, p=0.038). There was a trend towards complications of the peg with use of a standard peg (versus sleeved peg) (p=0.226). Conclusions: There are several potential complications of pegging. Most complications are minor and can be managed successfully.