During the course of the studies on the competition between intramolecular 1,2-H shift and intermolecular addition of benzylchlorocarbene to alkene, we obtained chemical evidence for

Tomioka, Kitagawa, and Izawa reaction of palladium with C6F51 followed by trapping the product with triethylph~sphine.'~ The analogous compound, C6F5PdBr, has also been prepared electrochemically from the metaLZ7 Platinum Compounds. Platinum slurries, obtained by potassium reduction of [P(C2H5)3]2PtX2 in ethereal solvents, exhibit similar reactivities with aryl halides to those of palladium. The yields of products are, as in the case of palladium, varied with the highest being for the more reactive aryl halides. The compounds possess the trans geometry as determ:ined by NMR s p e c t r o~c o p y~~ and in contrast to the palladium compounds exhibit no photosensitivity. SummaryHighly reactive slurries of palladium and platinum have been prepared by alkali metal reduction of compounds [P(C2H5)3]2MX2 in ethers using simple apparatus and procedures. These metals undergo oxidative insertion into carbon-halogen b0nd.s of aryl halides and yield compounds of the type trans-[ P (C2H5) 3] zM(R)X.Metal slurries prepared in the presence of triethylphosphine contain, besides the black insoluble metal powder, compounds of the metals in low oxidation states, most likely the known tris and tetrakis phosphine metal (27) J. J. Habeeb and D. G. Tuck, J. Organomet. Chem., 139, C17 (1977).compounds which are known to react with organic halides, and contribute to the yields of the products obtained here.Highly reactive transition metal powders have been prepared in the absence of stabilizing ligands and the chemistry of these metals is being studied. The ability to prepare with simple apparatus metal powders which undergo oxidative insertion reactions as well as reactions with neutral ligands is of great importance not only to synthetic organic, organometallic, and inorganic chemistry but also to catalysis and surface chemistry.Acknowledgment. We gratefully acknowledge support of this work by the US. Army Research Office. We thank Matthey Bishop, Inc., for a generous loan of platinum and palladium salts. Registry No. tran.~-[P(C~H~)~]~PdCl~, 15642-19-0; C6H61, 591-50-4; tr~ns-[P(C~H~)~]~Pd(C&~)I,70774-40-2; PdBr2, 13444-94-5; P(C2H6)3, 554-70-1; tran~-[P(C~H~)~]~PdBr~, 15638-55-8; C6H6Brr 108-86-1; trar~s-[P(C~H~)~1~Pd(C~H~)Br, 52230-30-5; PdCI2, 7647-10-1; C6H6CN, 100-47-0; ~~~~S -[ P ( C~H~)~]~P~( C~H~) C N , 70774-41-3; trans-[P-(C2H5)3]2Pd(CN)2, 15638-57-0; C6H5Cl, 108-90-7; trans-[P-(C2H5)3]2Pd(C6H5)C1, 15697-59-3; C6F5Br, 344-04-7; trans-[P-(CZH5),],Pd(C6F5)Br, 54071-54-4; trans-[P(CzH5),],Pd(C3H,)Br, 70774-42-4; PdI,, 7790-38-7; C6F,I, 827-15-6; tran~-[P(C~H~)~]~Pd-(C6F5)I, 54071-55-5; t r a n~-[ P ( C~H~)~]~P d 1~, 15638-56-9; [P(C2-15559-63-4; PtC12, 10025-65-7; ~~~~S -[ P ( C~H~)~]~P~( C~ 13964-98-2; tran~-[P(C~H~)~]~Pt(C~H~)cl, 13938-93-7; trans-[P-(C2H5)3]2Pt(C6H5)CN, 33914-65-7; ~~~~S -[ P ( C~H , )~]~P~( C~F~ 14494-01-0; allyl bromide, 106-95-6; [C6F5PdI],, 70728-62-0. H5)3]2Pd21kr 22180-56-9; PtI2,7790-39-8; ~Fu~.s-[P(C~H~)~]~P~(C~H~)

Investigation of photochemical processes of several -diazo carbonyl compounds reveals that the Wolff rearrangement to form ketene takes place directly from the singlet excited state of the s-Z conformer whereas the excited state of the s-E conformer dissociates nitrogen to generate singlet carbonyl carbene, which either undergoes characteristic carbenic reactions, e.g., insertion and 1,2-hydrogen shift, or gives rise to ketene. The migratory aptitude as well as the relative efficiency of other competing reactions from singlet carbene is shown to be an important factor in determining which reaction pathway is favored. Substantial amounts of singlet carbene can be formed even under sensitized conditions, presumably via intersystem crossing from initially formed triplet carbene.

Effects of substituents on the photochemical processes of several -diazo amides (la-f) have been studied[RCN2CONR'R" (1): a

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