Synthesis of Rh(acac)H(GeEt(3))(PCy(3)) and Rh(acac)H(SnPh(3))(PCy(3)) and their reactions with alkynes

The monoolefin complex Rh(acac)(cyclooctene)(PCy(3)) (1) reacts with HGeEt(3) to give Rh(acac)fl(GeEt(3))(PCy(3)) (2). On treatment of 2 with methyl propiolate and phenylacetylene the complexes Rh(acac){eta(2)-CH(GeEt(3))=CHR}(PCy(3)) (R = CO(2)Me (3), Ph (4)) are obtained. The X-ray crystal structure analysis of 3 reveals that the coordination geometry around the rhodium center is almost square-planar with the olefin disposed perpendicular to the coordination plane of the rhodium atom. Complex 1 also reacts with HSnPh(3). The reaction leads to Rh(acac)H(SnPh(3))(PCy(3)) (5). In the presence of methyl propiolate, phenylacetylene, and (trimethylsilyl)acetylene complex 5 affords the alkenyl compounds Ph(acac){(E)-CH=CHR}(SnPh(3))(PCy(3)) (R = CO(2)Me (6), Ph (7), SiMe(3) (8)). Similarly, the reactions of 5 with diethyl acetylenedicarboxylate and diphenylacetylene yield Rh(acac)(CR=CHR)(SnPH3)(PCy(3)) (R = CO(2)Et (9), Ph(10)). The addition of 1 equiv of 1-ethynyl-1-cyclohexanol to a pentane suspension of 5 leads to the hydroxyalkenyl derivative Rh(acac)-{(E)-CH=CHC(OH)(CH2)(4)CR(2)}(SnPh(3))(PCy(3)) (11). The structure of 11 was determined by X-ray analysis. The coordination geometry around the metal center can be rationalized as a square pyramid with the stannyl ligand in the apical position, Although the hydroxyalkenyl ligand of 11 is stable and does not-dehydrate to give the corresponding alpha,beta-unsaturated alkenyl compound, complexes of this type can be prepared from enynes. Thus, the reaction of 5 with 2-methyl-1-buten-3-yne leads to the alpha,beta-unsaturated alkenyl complex Rh(acac){(E)-CH=CHC(CH3)=CH2} (SnPh(3))(PCy(3)) (12), whereas in the presence of 1,1-diphenyl-2-propyn-1-ol complex 5 affords the allenyl derivative Rh(acac)(CH=C=CPh(2))(SnPh(3))(PCy(3)) (13).