The synthesis and X-ray structure of [PP-N] [W(CO)&H,CN] are reported. The complex crystallizes in the triclinic space group PT, with unit cell dimensions a = 12.771 (4) A, b = 13.410 (4) A, c = 13.850 (5) A, CY = 54.41 (3)O, @ = 68.65 (3)O, y = 83.98 (3)O, V = 1988 (2) A3, Z = 2, and RF = 4.13%. The W-C-H,CN bond distance was found to be 2.330 (8) A, a value quite similar to that found in the W-CH3 analogue. Unlike W(CO),CH,-, the W(CO),CH,CN-anion does not react with carbon dioxide even under very high pressure. Furthermore, the cyanoacetate derivative, W(CO),O,CC-H,CN-, prepared from cyanoacetate and W(CO),THF, does not undergo decarboxylation either in solution or in the solid state. On the other hand, the W(CO),O,CCH,C-N-complex is a catalyst for the homogeneous decarboxylation of cyanoacetic acid.In general, the carboxylation reaction of transition-metal alkyl compounds is not readily reversible. However, in selected instances, thermal decomposition of carboxylate complexes occurs with formation of metal-carbon bonds (eq l).I This is evident in those metal carboxylates involving coordinatively unsaturated metal centers, e.g., the reactions listed below (eqs 2 and 3).2v3(1)
~~uFM-R~(O,CR)(CO)(PP~~)~ -
trur~s-Rh(R)(CO)(PPh~)~ + C02 (3)In particular, for copper(1) carboxylates possessing functional groups other than the 4 2 0 , moiety capable of interacting with the metal center, facile decarboxylation reactions For example, there are several reports of decarboxylation processes involving the cyanoacetate ligand (eq 4),1a*5 where interactions of the type depicted in A are thought to be of importance.
AThe investigation presented herein was designed to probe the nature of electron-withdrawing groups on the alkyl carbon atom in the C02 insertion reaction involving [RW(CO)6]-.6 Additionally, the generality of the facile decarboxylation process previously noted for the cyano-