Nitrous Oxide Mediated Synthesis of Monomeric Hydroxoruthenium Complexes. Reactivity of (DMPE)₂Ru(H)(OH) and the Synthesis of a Silica-Bound Ruthenium Complex

Treatment of (DMPE) 2 Ru(H) 2 with 1 equiv of N 2 O affords the hydroxoruthenium complex (DMPE) 2 Ru(H)(OH) ( 1 ) in 41% yield. Further treatment with an excess of N 2 O affords the dihydroxo complex (DMPE) 2 Ru(OH) 2 ( 5 ) in 30% yield. Addition of phenols, thiols, and silanols to 1 yields the corresponding aryloxo-, thiolato-, and siloxoruthenium complexes 6 − 10 in 25−75% yield. The hydroxo ligand of 1 may also be exchanged with the surface silanols of silica to form the silica-bound complex (DMPE) 2 Ru(H)(OSilica) ( 14 ). Subsequent treatment of 14 with thiocresol removes the ruthenium complex as (DMPE) 2 Ru(H)(SC 6 H 4 Me) ( 10 ). The treatment of 1 with acetone affords the C-bound enolate complex (DMPE) 2 Ru(H)(CH 2 C(O)CH 3 ) ( 15 ) in 34% yield. Terminal alkynes react with 1 to give the ruthenium acetylide complexes trans -(DMPE) 2 Ru(H)(CCPh) 16 (74% yield) and trans -(DMPE) 2 Ru(H)(CCH) 17 (32% yield). Reactivity may also be affected at both ends of 1,7-octadiyne to give the bimetallic complex (DMPE) 2 RuC⋮C(CH 2 ) 4 C⋮CRu(DMPE) 2 ( 19, 33% yield). The addition of Ph 3 SnH, which does not contain an acidic hydrogen, to 1 affords (DMPE) 2 Ru(H)(SnPh 3 ) ( 20 ) in 32% yield. When 1 is treated with 1 equiv of p -tolualdehyde, the hydroxo oxygen is retained, the aldehydic C−H bond is broken, and the ruthenium carboxylate complex (DMPE) 2 Ru(H)(OC(O)C 6 H 4 CH 3 ) ( 21 ) is obtained in 28% yield. The structural assignment of 21 was confirmed by X-ray crystallography. Similar reactivity is observed when 1 is treated with hexafluoroacetone, in which case the C−C bond is cleaved to produce (DMPE) 2 Ru(H)(OC(O)CF 3 ) ( 22, 55% yield). Much of the observed reactivity of 1 is rationalized using the assumption that the first step involves reversible formation of a metal cation/OH - ion pair ( 23 ). Attempts to trap the cation with ethylene resulted in formation of the ruthenium ethylene complex (DMPE) 2 Ru(C 2 H 4 ) ( 2 ); there is strong evidence that 2 forms via a cationic hydridoruthenium ethylene complex. Treatment of 1 with CO forms the cationic hydrido carbonyl complex [(DMPE) 2 Ru(H)(CO)][OH] ( 25 ).