The dialkylmanganese compounds [Mn(CH,But),],and [Mn(CH,CMe,Ph),], react with organic isocyanates to give chelating amido products that can be verified by hydrolysis to the amides. For Me,SiNCO the products of reaction with [Mn(CH,But),],with 2 and 4 equivalents have been shown by X-ray crystal log rap hy to be, respectively, M n,( CH,B ut), [ p-OC( CH,B ut) N (Si Me,)] ,( p-CH,B u 9, and M n4 ( C H , B u t ) , ( p3 -N C 0) , [ p -0 C ( C H , B u t, N ( S i Me,) ] 4. I n the tr i a ng u la r, and q u ite u nsym metr ica I trinuclear species each manganese has a distorted four-co-ordinate geometry. Two manganese atoms are chelated by the amide ligands (Mn-0 2.208, 2.276 A; Mn-N 2.1 49, 2.1 84 A) the oxygen of which then bridge to a neighbouring metal atom. Two of the manganese atoms carry one terminal alkyl (Mn-C 2.1 22 and 2.1 54 A) and one edge of the Mn, triangle is bridged by one symmetrical (Mn-C 2.309 and 2.31 1 A) and one unsymmetrical (Mn-C 2.184 and 2.646 A) bridging alkyl. The tetranuclear species is centrosymmetric. One of the unique M n atoms carries a terminal alkyl (Mn-C 2.092 A) and Is further co-ordinated by two bridging amide oxygens (Mn-0 2.070 and 2.073 A) and one triply bridging cyanate nitrogen (Mn-N 2.282 A). The other independent manganese is chelated by two amides with Mn-0 2.308 and 2.359 A, Mn-N 2.1 46 and 2.1 76 A and its six-co-ordination is completed by bonds to both triply bridging cyanate groups with Mn-N 2.298 and 2.138 A. The reaction of Cr(mes),(thf) (mes = 2,4,6-Me,C,H2, thf = tetrahydrofuran) with BUNCO gives Cr[OC(mes)NBut],. Similar interactions using ButNC lead to Mn[ButCH,C=NBut],(PMe,) and Cr[(mes)C=NBut],.Reactions of transition-metal alkyls and aryls with heterocumulene type ligands (eg. COz and R,C=C=O have been well studied but those with organic isocyanates have received somewhat less attention., Metalkarbon (T bonds were shown to react as in equation ( 1 ) to give chelate amido compounds A.but the insertion products have been structurally characterised in only a few cases., Some recent studies involve insertions into Mo02(mes)," (mes = C,H,Me,-2,4,6) and U(cp),-(CHPMe,Ph) (cp = q-C5H5);5 for the latter the structure of the product with PhNCO was determined. Unpublished work quoted in a paper on isocyanide insertions into V(mes),(thf) (thf = tetrahydrofuran)6 indicates insertion also of C6H, 1-NCO, the product hydrolysing to (C6H ,)HNC(O)(mes). Reactions of manganese dialkyls and chromium trimesityl with isocyanates and with Bu'NC are now described.
Results and DiscussionManganese Compounds.-The dimeric or polymeric manganese dialkyls '' including [Mn(CH,Bu'),], and [Mn(CH,C-Me,Ph),], have been shown to undergo a variety of reactions with Lewis bases and compounds with acidic hydrogen atoms.'< We now show that isocyanates react readily. When hydrocarbon solutions of [Mn(CH2Bu'),], and [Mn(CH,C-
