Reactions of diacetylene ligands with trinuclear clusters. 3. Cyclization of diynes with beta-amino moieties on the metal core of [H2Os3(CO)(10)]

Reactions of [H2Os3(CO)(10)] with the substituted diynes R-C-2-C-2-R ' (1, R = Ph, R ' = CH2NHPh; 2, R = Ph, R '= CH2NHCH2Ph; 3, R = R '= CH2NHPh) aff ord the clusters [HOs3-(CO)(10)(L)] (L = {mu-eta (1):eta (2)-PhCH2C(H)=C-C( H)=C-NPh} (4), {mu-eta (1):eta (2)-PhCH2C(H)=C-C(H)-C-NCH2Ph} (5), and {mu- eta (1):eta (1)-CH3CC=C-C(H)=C(H)-NPh} (6), which have been characterized b y single-crystal X-ray diffraction analyses as well as by various spectrosc opic methods. In clusters 4-6, the starting diynes 1-3 have been rearranged to form substituted pyrrolyl rings which bridge two osmium atoms in eta (1 ):eta (2)- (4, 5) or eta (1):eta (1)- (6) coordination modes depending on t he nature of substituents in 1-3. A possible reaction pathway for the diyne cyclization reactions that yield 4-6 involves initial transfer of a hydrid e onto a coordinated diyne followed by a series of 1,3-shifts and subsequen t nucleophilic attack of the nitrogen on the third carbon atom of the diyne system to afford the five-membered pyrrolyl ring. Cluster 6 and its previo usly characterized furanyl analogue [HOs3(CO)(10){mu-eta (1):eta (1)-(OCH-C HCC)-C-CH3)}] (7) undergo facile thermal transformation accompanied by the loss of a CO ligand to give the clusters [HOs3(CO)(9){mu (3,)eta (3)-CH3CC= C-C(H)=C(H)-NPh}] (8) and [HOs3(CO)(9){mu (3,)eta (3)-(OCH=CHC=CCCH3)}] (9) . In both 8 and 9, single-crystal X-ray analysis revealed the presence of p entagonal pyramid cluster cores containing three osmium and three carbon at oms.