Reaction of M3&[;μ-H,μ-O=CNMe2&];(CO)10 (M = Ru or Os) with but-2-yne. Crystal and molecular structures of M3&[;η3-CH2CHC(H)CH3&];&[;μ-(CO),μ-O=CNMe2&];(CO)8(M = Ru or Os) and Ru2&[;μ-O=CCMe=CMe(η2-CMe=CHMe&];-&[;μ-O=CNM2)(CO)5

Abstract The complexes M 3 &[;μ-H,μ-O=CR&];(CO) 10 (R= NMe 2 , M = Ru ( 1a ) or OS ( 1b )) are observed to react with dimethylacetylene ( 2 ) under varying conditions. The reaction of 2 is observed with 1a at 23°C requiring 12 h for completion in hexane. Three isolable products are obtained along with a trace of Ru 3 (CO) 12 : Ru 3 &[;η 3 -CH 2 CHC(H)CH 3 &];&[;μ-(CO),μ-O=CNMe 2 &];(CO) 8 ( 3a , 35%), Ru 2 &[;σ,π-μ-C(Me)=CHMe,μ-O=CNMe,μ-O=CNMe 2 &];(CO) 6 ( 4a , 14%), and Ru 2 &[;μ-O=CCMe=CMe-(η 2 -CMe=CHMes&];&[;μ-O=CNMe 2 )(CO) 5 ( 5a , 9%). For reaction of the tri-osmium complex 1b with 2 , heating to 140°C is required using excess 2 as its own solvent under autoclave conditions; only the η 3 -allyl derivative 3b is obtained (28% conversion; 98% yield). Structures of three of the new products have been determined using Picker (FACS-1) or Synthex P 1 − four circle automated diffractometers and graphite-monochromatized MO- K α radiation. Complex 3a crystallizes in the monoclinic space group P 2 1 / n ; cell dimensions a 10.4734(13) A, b 15.3589(19) A, c 13.7645(17) A, and β 99.041(3)°; calculated density 2.07 g cm −3 ; 3831 unique reflections with I ⪢ 3σ( I ) were used in the refinement; final discrepancy indices, R = 0.042 and R w = 0.055. This is one of three different crystallographic modifications with essentially the same molecular parameters. Complex 3b crystallizes in the monoclinic space group P 2 1 / n ; cell dimensions a 15.3496(13) A, b 28.9195(22) A, c 9.7116(8) A, and β 98.114(3)°; calculated density 3.05 g cm −3 ; 5897 unique reflections with I ⪢ 3 σ( I ) were used in the refinement; final discrepancy indices, R = 0.047 and R w = 0.062. Complex 5a crystallizes in the monoclinic space group P 1 − ; cell dimensions a 7886(2) A, b 10.987(3) A, c 12.337(3) A, α 98.88(2)°, β87.18(2)°, and γ 104.36(2)°; calculated density 1.78 g cm −3 ; 3872 unique reflections with I ⪢ 3σ( I ) were used in the refinement; final discrepancy indices, R = 0.035 and R w = 0.060. Metal atoms in all three structures were located by direct methods (MULTAN80). All other nonhydrogen atoms were then located by difference maps. Hydrogen atoms in the organic groups were included in structure factor calculations in calculated positions. Each of the crystal studied consists of discrete molecules of the complexes; crystals of 3a and 3b each consist of a triangle of metal atoms containing an η 3 -methallyl fragment attached to one of the atoms along an edge also bridged by a CO group and a dimethylcarboxamido group. For 5a , a dinuclear unit is observed which is bridged by a &[;μ-O=CCMe=CMe-(η 2 -CMe=CHMe&]; group as well as a dimethylcarboxamido group. The metalmetal separations in the three structures are summarized as follows, A, respectively: unbridged RuRu (in 3a ) 2.867(1) and 2.829(1); bridged RuRu separations 2.783(1) (in 3a ), and 2.681(1) (in 5a ). In 3b the OsOs separations for the two independent molecules of the unit cell are, respectively, A: 2.848(1), 2.846(1) and 2.833(1), 2.871(1) (unbridged) and 2.814(1), 2.786(1) (bridged). The position of the allyl group in products 3a or 3b as well as the point of attachment of the μ-O=CCMe=CMe-(η 2 -CMe=C(H)Me group suggest that initial substitution of acetylene occurs on the metal to which the oxygen of the μ-O=CNME 2 group is attached. This follows the path of PR 3 or 13 CO substitution observed for these and related edge doubled-bridged derivatives.