new developments in
ORGANOLEAD CHEMISTRY G. J.
M. VAN DER K E R K
A n expert in the j e l d discusses the latest trends in the use of lead and organolead compounds f o r biocides and fungicides, in corrosion inhibition, as catalysts in esterijcation and pobmerization, and as stabilizers f o r plastics n organometallic compounds, a direct bond relation
I exists between a metal and one or more carbon
atoms. This definition excludes metal salts of organic acids which are more properly defined as organic metal compounds. As an example, two well known lead derivatives can be cited : Pb (CzHb)4-tetraethyllead (Organometallic compound) Pb(OC-CH~)4-lead
tetraacetate
I1
0 (Organic metal compound)
Thus, the designation of a lead compound as either organic or organometallic is determined by the presence or absence of metal-carbon bonds and not by inherent properties. Because the periodic system numbers about 7 5 metallic elements, the potential scope of organometallic chemistry can readily be envisioned. I n addition to the number of elements which can be incorporated into organometallic systems, an equally large variation exists in the types of bonding. Fortunately, three schematic types of bonds between metals and carbon can be distinguished (79). For a long time organometallic compounds have been known in which the carbon-metal bond has either a pronounced ionic character, such as in the alkali metal alkyls, or a pronounced cr-type covalent character, typical of the tetraalkyl compounds of the fourth group elements, among which are the tetraalkylleads. Since 1950 a third type of metal-carbon bond relation has been recognized. Vacant &orbitals of transition metals interact with n-electron systems of unsaturated hydrocarbon compounds, resulting in the formation of stable structures. The classic example is biscyclopentadienyliron or ferrocene. As a first approximation, bonding in fourth main group organometal compounds RIM (R = alkyl or aryl) may be described in terms of spa hybridized molecular orbitals (6). This leads to the characteristic
tetrahedral arrangement around the central metal atom, the four metal-carbon bonds being identical and highly covalent. I n less symmetrical types of compounds, RnMX4_, (X being an acid radical, halogen, etc.), more complicated hybridizations occur and bond properties change accordingly. I n each group of the periodic system the behavior of corresponding organometallic derivatives can be evaluated to a certain extent on the basis of increasing atomic radius, decreasing electronegativity of the metal concerned, and easier polarizability of the metal-carbon bonds. Going from carbon to lead the interatomic distances increase, and this leads to a gradual weakening of bond strength. This is reflected most impressively in the strong decline of bond energies of the fourth group element-element bonds (24):
c-c
80 kcal. /mole 50 kcal./mole 40 kcal./mole 20 kcal./mole
Si-Si Sn-Sn Pb-Pb
Consequently, in this group the lead-carbon and the lead-lead bonds have the lowest photo- and thermostability. The increasing polarity and polarizability of the metal-carbon and of the metal-metal bonds cause fourth group organometallic compounds of lead to be most vulnerable toward attack by polar reagents, such as halogens and acids. Thus, organometallic lead compounds are the least stable but also the most reactive compounds in this group. The organic chemistry of the fourth main group elements is extremely well developed (8). First, more extensive study has been devoted to the organic derivatives of all the relevant elements in this group than to any other group. Second, the organometallic derivatives of this group are of great practical significance because they have the widest range of industrial applications (73). Excluding carbon, the organic forms of the three remaining elements-viz., silicon, tin, and leadhave ail ained levels of outstanding industrial importance, as illustrated in Table I. VOL. 5 8
NO. 10 OCTOBER 1 9 6 6
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As shown, organolead compounds are of vastly greater commercial significance than the organosilicon, -tin compounds. Until recently, a single organolead compound, tetraethyllead, was manufactured on a gigantic scale for just one application-i.e., as an antiknock additive to gasoline (26). At present, tetramethyllead is partly replacing the ethyl compound, but this does not change the overall picture. It is an interesting anomaly that the discovery of this application in 1923 by Thomas Midglq- (74) and its tremendous development afterward did not stimulate a more comprehensive study of organolead chemistry. I n fact, aside from this work on tetraethyllead, industry, until recently, has practically ignored the organolead field, and even fundamental organolead chemistry (27) has lagged behind that of silicon, germanium, and tin. I n 1960 the International Lead Zinc Research Organization, Inc. (ILZRO), initiated a program of exploratory research on organolead chemistry at the Institute for Organic Chemistry, T.N.O., at Utrecht. The aim of this program was to find new applications for the organoleads through the synthesis of new compounds. From the start, two approaches were used. First, an extensive study of the synthesis, reactions, and properties of the several types of organolead compounds was made. Second, samples of promising compounds were made available (75) on a worldwide scale to industrial and governmental research institutes. This cooperative work helped to stimulate fundamental and applied research on organolead compounds and to widen the scope of scientific and industrial interest in organolead chemistry. Preparation and Some Reactions of Organolead Compounds
Stable organolead compounds are derived from tetravalent lead and the great majority falls within the following basic types: RdPb, RsPbX, RZPbX2, RPbX3 (R = alkyl or aryl; X = halogen, O H , or an acid radical). Few compounds containing lead-lead bonds are known; until recently the only type was RaPb-PbRZ, the hexaalkyl (or -aryl) diplumbanes. Best known for the technical preparation of the compounds, R4Pb (R = ethyl or methyl) is the reaction of the lead-sodium alloy PbNa with ethyl chloride or methyl chloride, respectively (27). 4 PbNa
+ 4 CZH&l+-
(C2Hj)4Pb
+ 4 NaCl + 3 Pb
TABLE 1. Lyse of Organometallics
7964 Consumption of Organometallics, Metric Tons
Organometallics as an Outlet f o r the Metal,
%
25,000
Si Biocides Pb
30
Consumption of Metal, Metric Tons
Miscellaneous Me4Pb
5,100
0.7
320,000
9.2
350
1
165,000 2,425,000
INDUSTRIAL A N D ENGINEERING CHEMISTRY
This method has been operated for decades on a tremendous scale with but minor variations. More recently, initiated by Ziegler's work, much attention has been paid to electrolytic methods using conductive complexes of triethylaluminum (38) or of ethylmagnesium chloride (7). I n contrast with the excellent results achieved in the technical preparation of these compounds is the surprising lack of even suitable laboratory methods for the synthesis of the remaining types of organolead compounds. A reinvestigation by Willemsens at Utrecht of the well known reaction of PbClz with Grignard reagents showed that, depending on reaction conditions, either compounds R4Pb or compounds RaPb-PbRZ are formed (30): +R4Pb Pb 80' PbC12 RMgCIETo RzPb 9 \-*RaPb-PbRs Pb 2
+
/T
+
+
The primary products formed are the unstable species RnPb. Tt'hen the ether solvent is redistilled and the residue is heated at about 80" (reaction 1) mainly R4Pb and Pb are formed. If the primary product is heated for a prolonged time not above 40" C.-e.g., in refluxing ether-the hexaalkyl- or hexaaryldilead compounds R3PbPbRs and lead are almost exclusively obtained (reaction 2). I n fact, preparation along this route of the compounds R3PbPbR3 is much easier and more straightforward than that for the compounds RdPb. The present easy availability of the hexa compounds has led to a much better method for the preparation of compounds R3PbX as d l . Instead of splitting off one hydrocarbon group from RdPb, the careful halogenation of hexaalkyldileads gives trialkyllead halides (34): RaPb-PbRa
%* 2 R3PbX R
=
alkyl
With R = phenyl this reaction is not satisfactory because phenyl groups are also split off, which leads to the formation of mixtures of tri- and disubstituted phenyllead halides. Recently Willemsens found an excellent method for the selective cleavage of the lead-lead bond in hexaphenyldiplumbane by reacting this compound with potassium permanganate in acetone solution (37): PhaPb-pbPh3 KMnOa in acetone 2 PhsPbOH Hz0 For the compounds RZPbX2 and RPbX3 no satisfactory direct methods of preparation are thus far available. They are obtained by the careful elimination of alkyl or aryl groups from higher substituted species (35). Work toward a more satisfactory synthesis of these compounds is, however, in progress. The scope of this paper does not permit a full review of the vast amount of new organolead chemistry developed by Willemsens. A few examples will be given of the striking versatility of the organolead reagent triphenylplumbyllithium, PhaPbLi (32). This compound was first prepared in 1952 by Gilman et al. (9) from lead dichloride and phenyllithium in ether:
PbClz
+ 3 PhLi ~theiPhaPbLi + 2 LiCl
Even more convenient, as it is readily available, is reacting the compound hexaphenyldiplumbane with lithium in tetrahydrofuran, according to Tamborski (25): PhaPb-PbPh3
+ 2 Li T” 2 Ph3PhLi
A curious reaction occurs when triphenylplumbyllithium is subjected to simultaneous hydrolysis and oxidation a t low temperature by treating it with an icesalt mixture containing hydrogen peroxide (37) : PhsPbLi
Red compound PhnPb5
r ~ ~ ~ t2 1 t
The fiery red compound can be extracted with chloroform and crystallized from the same solvent. Analysis and molecular weight determinations pointed to the formula (CsH5) 12Pb5, dodecaphenylpentalead. The structure could be established by careful iodination. One mole quickly consumed three moles of iodine, with formation of four moles of triphenyllead iodide and one mole of lead iodide. These products were isolated in yields of 92 and 930j0, respectively: (CsH5)lzPb
+ 3 Iz
4
4 PhSPbI
Even more amazing than the high yield of this reaction (70%), is the fact that this compound is formed at all. Taking into account the accepted covalent atomic radii of carbon and lead, it would seem that sterically the central carbon atom cannot accommodate four large lead atoms. The compound has remarkable thermal and chemical stability. I n fact, it is the most stable organolead compound ever encountered in this research program (thermal decomposition only at about 300’ C.; chemically stable for 8 hours to glacial acetic acid a t 150 O C. under pressure). If, instead, an excess of carbon tetrachloride was used, the following reaction took place (33): PhsPbLi
+ ccl4
+
(Trichloromethyl)triphenyllead is an easily available and stable compound and is of considerable interest for synthesis. Well above room temperature it thermally decomposes into triphenyllead chloride and the reactive organic species dichlorocarbene (28) :
800’ PhaPbCl
Tetrakis(triphenylplumbyl) lead (or dodecaphenylneopentaplumbane)
The compound is comparatively stable, perhaps because of its high degree of symmetry. So far, no organolead compounds are known with more than one leadlead bond. Employing similar and other reactions, Willemsens was able to make a whole series of compounds of this general structure containing the fourth group elements germanium, tin, and lead in every combination (36). I n this series only compounds containing a metal-lead bond are colored. (PhMW‘ M‘ Pb Pb Sn Pb Ge Pb Pb Sn Sn Sn Pb Ge Sn Ge
M
Color
Yield,
Isomor$hy
Red Yellow Bright yellow Yellow White Bright yellow White
+ t ++
I I
PhaPb-C-PbPhr PbI’ha
+ cc14
+ C(PbPhs)4
This reaction was discovered by Seyferth (20) with the corresponding organomercury compounds. Dichlorocarbene is characterized by its specific reactivity toward aliphatic double bonds, with which it forms a cyclopropane structure-e.g.,
Cyclohexene
7,7’-Dichloronorcarane
Because of the present interest in carbene reactions, it is expected that this new carbene-generating reagent will merit attention. I t is hoped that these few examples will impress upon the reader the exciting scope of organolead chemistry and the wealth of knowledge and progress which awaits further exploitation.
%
30 55 -20
?
54 22 16 4
Highly interesting results were obtained when triphenylplumbyllithium was reacted with carbon tetrachloride. When a n excess of the lead lithium compound was used, the reaction took the following course (38):
4 PhsPbLi PhPha
+ CClz
Dichlorocarbene
This, at once, led to the structure : PbPh3 PhsPb-Pb-PbPhs PbPha
+ LiCl
(Trichloromethyl)triphenyllead Yield, 90%
Ph3Pb-CC13
+ PbIz
PhsPb-CC13
+ 4 LiCl
Tetrakis(triphenylplumby1)methane
Application Aspects (4, 1 I )
As stated, the Utrecht program from the outset aimed a t developing new industrial applications for organolead compounds. For obvious reasons, the program has not explored the subject of antiknock agents. Extensive screening for possible applications has resulted from ILZRO’s policy to make available to research laboratories, worldwide, a variety of organolead compounds which would, otherwise, be difficult to obtain (15). Some idea of the extent of ILZRO’s support for this work can be gained from the fact that, during the past 2 years, the Institute for Organic Chemistry, T.N.O., has distributed about 100 different organolead compounds. Quantities varied from one half a gram to several kilograms (about 1100 samples). The total amount of organolead compounds made and shipped by its semitechnical department to date is 60 kilograms. VOL. 5 8
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OCTOBER 1 9 6 6
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I t should be mentioned that no relation exists between the water solubilities of these compounds and the activity pattern observed. So far, the results are in general agreement with those found earlier in Utrecht with the corresponding triorganotin compounds. When diorganoleads were tested, an unexpected and high activity toward bacteria, both gram-positive and gram-negative, was found. Toward fungi, these compounds exhibit the same modest degree of activity as the corresponding diorganotins which are rather inactive toward bacteria. I n particular, the high activity of the diorganoleads toward gram-negative bacteria is of interest because these show a general high resistance toward any type of disinfectant and antibiotic. Table I V shows some test results obtained with diorganoleads.
TABLE I V
RzPbDiacetate =
Methyl Ethyl
0 2
1 n-Heptyl I ,
0 1
n-Butyl n-Pentyl n-Hexyl n-Octyl Phenyl
R =
B. alliz
Methyl Ethyl
100
I 1
20
ztaltcum
~
200 20
nigrxans
A . niger
1
200 20
~
>500 50
Gram-Positive
B. subtzlis
o
2
0 5
202 1
M. Phlez 01 0 0 0
2 2 1 2
0 5 2 20 2
~
s.
lactzs
1
Gram-ivegative
1
coli
1
~
Ps . juorescens
50
50 5
5 1
2
2
500
10
0 5
5
1 10
50 1
100 ~
1
>500 10
1
>500
>500 >500 100
Because of these results, a broad program has been set up for the evaluation of the organoleads as practical biocides. When biological activity, chemical stability and industrial availability are taken into account, the following types of compounds have been selected : RaPbX, tripropyl-, tributyl-, and triphenyllead compounds; R2PbX2, dipropyllead compounds. The choice of the group X determines to a large extent the physical properties-e.g., solubility. The availability of pilot samples of organolead compounds synthesized in the program has stimulated cooperative testing by many industries to develop commercial applications. A review of the results achieved thus far will give some idea of the potential of these compounds and their industrial applicability. Paints
Gram-Posztzve
RBPbAcetate =
Methyl Ethyl n-Propyl n-Butyl n-Pentyl n-Hexyl n-Heptyl fl-Octyl Phenyl
32
B, subtzlzs ;1 ;
2 0.5 0.5
5 20
50 1
I
i1
S.
M. bhlei
~
lactzs
1 1
Gram-.\-e500
50 >500
>500 >500
>500
200 1
>500
20
50
1I : 1
100 20 10 20
5
...
INDUSTRIAL AND ENGINEERING CHEM STRY
Trials with organoleads are being conducted in two important areas : fungicidal emulsion paints and antifouling paints. For both applications, tributyllead compounds appcar to be optimum, the acid radical being adjusted to the required physical behavior. AUTHOR Dr. G. J . M . van der Kerk is on the s t a f of the Institute f o r Organic Chemistry, T.N.0 ., Utrecht, T h e hretherlands. H e acknowledges the j n a n c i a l assistance of the International Lead Zinc Research Organization Inc., hrew Y o r k , N . Y . and the interesl of Dr. S. F. Radtke of that organization i n the preparation of this paper. T h e author also acknozuledges the consent of the organizers of the Conference of the Lead Development Association, London, to publish the paper i n I B E C .
Figure 7 . Panel (left) containing 33y0 TPLA and 6701, CulO disfilayed comfilete resistance to barnacles and tube worms after 78
months at Miami Beach. Fouling by barnacles and tube worms has commenced on control panel (right)
Antifouling activity was determined by replacing all or part of the cuprous oxide in standard formulations with selected organolead compounds for immersion studies. Three paint systems-vinyl standard, vinyl high rosin, and oleoresinous paints-were utilized. Compounds included triphenyl- and tributyllead acetate and triphenyl- and tributyllead laurate. Comparative data on the antifouling performance of the control panels and panels treated with paints containing organoleads are shown in Table V. Results are not yet available for oleoresinous paints.
For vinyl standard paints, the best rating (100% resistance to fouling) was attained with triphenyllead acetate (33% TPLA, 67% CuzO), compared with ratings of 5 5 at Pearl Harbor and 92 at Miami Beach for the controls. This comparison is depicted in Figure 1 taken at Miami Beach. The organolead-treated panel shows no attack, while the control panel shows barnacles and tube worms. For vinyl high rosin paints, tributyllead acetate plus cuprous oxide rated perfect at Pearl Harbor and Miami Beach, as did the control panel. All of the organoleadcuprous oxide panels are thus far giving excellent results with four ratings of 100 and all others 90 or better.
TABLE V
1
Toxicant
1
Pearl Harbora 13 Months
Miami Beacha 78 Months
121 Series (Vinyl Standard) 121 Control CuzO/TPLA CuzO/TPLL CuzO/TBLA CuzO/TBLL TPLA
92 100
55 100 20 75 75 96
83 86 97
72
121/63 Series (Vinyl High Rosin)
~
(I
100 is clean panel; 0 is completely fouled.
~~~
Textiles
Extensive field tests have shown that a number of organolead compounds can be chemically modified to make them cellulose reactive to impart rot, mildew, weather, and flame resistance to cotton. Wash-fastness is also greatly improved. Thioethyl-, thiomethyl-, and thiopropyltriphenyllead (plus several other organolead compounds) imparted good rot resistance to cotton fabrics at add-ons of about 4.5 to 570. The thioethyltriphenyllead-treated fabric retained 100% breaking strength after 23 weeks of soil burial. Mildew and algae growth, a problem with the controls, was also inhibited. A resin binder and titanium dioxide are being incorporated into the treating bath to VOL. 5 8
NO. 10 O C T O B E R 1 9 6 6
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improve weather resistance. Previous screening has shown Ti02 to be one of the best light screening pigments for use on cellulose. Wood Preservatives
I n warm subtropical waters especially, creosote provides inadequate protection for standing piles against attack by marine borers. Most marine timbers are subject to complete destruction through biological corrosion in 8 to 10 years. Of several organoleads tested, tributyllead acetate has shown the best resistance to limnorial and teredine borers. This compound, using creosote as a carrier, also showed exceptional resistance to leaching. Further immersion studies are needed to isolate an optimum compound. U s e a s Industrial Biocides Untreated
Because of their powerful bacteriostatic activity, triand dipropyllead and tributyllead derivatives offer promise for the preservation of jet fuel, as cutting fluid additives, and for preventing pitting corrosion of ships. Based on the broad biocidal and biostatic activity of the organolead compounds, many more applications are being investigated. Bilharzia control is a promising area. This disease is extremely debilitating to man and animal and is of great social and economic importance in tropical areas. Several organolead compounds are active against the snails which act as intermediate hosts for the causative parasite (7, 78). Field trials are under way. More than a dozen compounds such as triphenyllead chloride and triethyllead acetate which show exceptional activity for rodent repellency have been isolated. Figure 2, for example, shows complete protection for jute against rodent attack with 1% triethyllead acetate. Catalytic Properties of Organolead Compounds
O.Iyoof
?yoof Figure 2.
toxicant
toxicant
Rodent repellent action of triethyllead acetate applied to
jute
34
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Several literature references mention the activity of organolead compounds, particularly dialkyllead derivatives, as esterification and transesterification catalystse.g., in the manufacture of polyethylene terephthalate ( 7 ) , an important fiber-forming polymer. Another much referred to effect of organolead compounds is their catalytic activity in polymerization reactions-e.g., of olefins and vinyl compounds (75). This activity, presumably, is connected with the thermal rupture of lead-carbon bonds leading to the formation of alkyl radicals which then act as polymerization initiators. A highly interesting catalytic effect has recently been discovered and studied at the Institute for Organic Chemistry, T.N.O., in the field of polyurethane foam manufacturing. Basically, two simultaneous reactions are involved in the process: the reaction of a polyetheralcohol with a diisocyanate, leading to high molecular weight polyurethanes ; and the reaction of isocyanate groups with water, leading to the formation of carbon dioxide which acts as a blowing agent. Either reaction requires a suitable catalyst. Until recently, no catalysts were known which properly activated both reactions. Usually in the urethane reaction certain tin compounds-stannous dioctoate or dibutyltin dilaurate-
WAND-TAPPEl TEST-SI€
10 OIL. llO°C
Lwd, Kg.
Figura 3. Additions of 2 and 1% of a palmtable wganolead cornpound (designakd N-4) to lubricating oil, signijcatlrly reduce wear under load
function as a catalyst; the water reaction, as a rule, is catalyzed by rather complicated types of tertiary amines. As a result, the whole process is fairly complex and difficult to regulate. In a systematic search for other types of catalysts, involving a study of each individual reaction, the surprising discovery was made by Overm a n (76) that one particular type of organolead compound was catalytically active in both reactions. Subsequently, it was found that this type of compound could successfully be applied as a sole catalyst in the formation of foams under technical conditions. No other type of organolead compoucld showed any appreciable catalytic activity in either reaction. Thus, it seems that we are dealing with a highly specific effect which is likely to become of practical significance. The commercial aspects are now being evaluated by firms supplying the polyurethane market. Stabilizing Properties of Organolead Compounds
Divergent opinions have been expressed regarding the value of organolead compounds as heat stabilizers for polyvinyl chloride. Certain inorganic and organic lead compounds (2, 77)--e.g., lead stearate-and certain organotin compounds are applied for this purpose on a large scale. Research is presently under way to define the merits of organolead chemicals in this highly competitive but important field. A specific compound developed by the T.N.O. Institute at Utrecht has shown exceptional antiwear properties as a lubricant additive in research sponsored by ILZRO at the Ethyl Corp., Detroit, Mich. I n a study made of the mechanism of antiwear action, this compound appears to form a thin, durable film on the scar area of test balls but not on the rest of the surface. This film gives long range antiwear protection, even when the additive oil is removed and replaced with ..
clear oil. Electron diffraction studies show the presence of an unknown, crystalline compound. To gain acceptance for this organolead additive by the automotive industry, wear tests were conducted with a standard cam-and-tappet bench test, carried out in a &ball machine under progressively higher loads. Note the improved performance obtained with the organolead additive shown by the two larger curves in Figure 3. At present, patents are being obtained on this compound prior to cooperative development work with manufacturers of lube oil. In summary, it can be said that after decades during which a single organolead application attained tremendous significance, research has introduced a wide variety of promising new organolead compounds. Significantly, the potential applications reach into almost all segments of industry and utilize all possible structural types of compounds. Because of ready availability and low cost, there is a natural tendency to utilize tetramethyl- and tetraethyllead as a starting material in developing new industrial applications. Although propyl-, butyl-, and phenyllead compounds have not yet been made on an industrial scale, suitable methods are available for their manufacture and it has been established that they can be made inexpensively. REFERENCES ( 1 ) Bot,, L. L., H ~ d m r b a nPmem. P d d . Rcfiwr44, 115 (1965). (2) Brauo. D., Ehrahim, A., Langbcin, G., K m m j e 34, 147 (1964). (3) Ckm. E=. N w 3 9 (38),36 (1961); 42 UP), 52 (1964). (4) Ckm. B d . ( D u d & $ ) 17,272 (1965). (5) Ckm. Week,p. 95 (Oct. 24, 1964). (6) Cotton, F. A., Wilkiinmn, G., “Advanced Inorganic Chemistry,” Intsyimcc, N m York, 1962. 0)de Villicra, J. P., Mackmtie, J. 0.. W.H.O.Mdlwicidr In/. Bull. No. 13, (1963). (8) Dub, M., "Organometallic Compound%,’.Vol. U, Springer V a h g , B a l k , 1961. (9) Gilman, H.,Summcra, L.,Lcepcr, R.W., J. Orb. Ckm. 17,6M (1952). (10) Hawood, J. H., “Indurtrial Application. of Organomcraui Compound%” Chapman & Hall, London, 1963. (11) Harwwd, J. H.,“Mctalorganic Compunds,” Ado. Ckm. Sn., No. ZS(1959). (12) H0pf.H. S.,Duncan, I., W.H.O. Mdlmticidelnf. BuN.No.21,VI1(1966). ’l A r d S i c . 125,198 (1965). (13) Marshall, E.F., Wuth, R.A.,Am. N. . (14) Midglcy, T . , Hochwalt, C. A., Cdiig-t, G., J . Am. Ckm. Sor. 43, 1821 (1923). (15) “Orgnoolead Compounds,” Intern. Lead Zinc R e . Organ., New York, 1964. (16) Ovcrmar~H.G.I.,vandcrWant,G.M.,ChimiolJ,126 (1965). , 80 (luly 15, 1961). (17) Penn, W. S., Rub& P b b m Wekflyp. (18) Ritchie, L. S., Jimena, W., Joseph, I., W.H.0.Mdlwciicde 1st. Bull. No. 18, 111 (1964). (19) Rochow, E . G . , H u r d , D . T . , ~ R . N . , “ T h c C h c m i ~ t r y o f O r g a n o m c f a l l r Compounds,” Wilcy, NEWYork, 1957. (20) Seyfcrfh, D.,Burliieh,l.M.,Hccrcn, J.K., J . Org.Ckm.27,1491 (1962). (21) Shspiro, H., “Mctalorganic Compounds,” Ad”. Ckm. Sn.,No. 23 (1959). (22) Sijptcjn, A. K., L y e n , I. G. A,, van dcr Kcrk, G. I. M., in “Fungicide, an Advanced re.dtm,” Academic Prc.., N w York, in press. (23) Sijpcatc-K. Riikens, F. Luijfen, J. G . A., Willcmma, L. C. Alumre rn k’J. 8cmbh.S;d. 28,346 (1962). (24) Skinner H. A,, “Advances in Organomclallic Chemistry.’. Academic PIC” N w York,’1946. (25) Tamhon*i, C., Ford, F. E., Lchn, W. L., Moore, G. L., %I&, E. I., J . Orb. Ckm. 27,619 (1962). (26) Turn=, S. W., Fader, B. A,, INO.Em. CHEY.34 (a), 52 (1962). (27) Willemacns L. C., “Organolead Ch-try,.’ Intan. L a d Zinc R e . Ow., New York, 19k4. (28) Wilhmacna, L. C., unpubliahcd reulfs. (29) Willcmsem, L. C. van dcr K a k G. J. M. “Invatigationr in the Field of OrganometallicChcn;irtry,” Inlcm. i c a d Zinc Ow., N w Y a k , 1965. (M)Ibid., pp. 15, 64. (31) W d . , pp. 24, 71. (32)Ibid., p. 31. (33) Ibid., p. 41. (34) Did., p. 66. (35) lbid., pp. 75, 79. (36) Willcmenr, L. C., van d a K a k , 0.I. M.,J . Orpmnukd. Ckm. 2,260 (1964). 1377) Ibid.. 0 . 271. (38) Willmuens, L. C!., van der Kcrk, 0.J. M., Rn. Tmu. Chim. 84,42 (1965). (39) Z y k r , K.,Lchmkuhl, H., Angm. Ckm. 67.424 (1955).
Le.
. .
,
V O L 5 8 NO. 10 O C T O B E R 1966
35
