REACTIONS OF DIYNES WITH [RHCL(PIPR3)2] - UNSATURATED C4 AND PARTLY UNSATURATED C6 CHAINS BETWEEN 2 RHODIUM CENTERS

Treatment of [RhCl(PiPr3)2]n (1) (n = 1 in solution) with HC=CC=CH leads to the formation of the diynediyl dihydrido complex [(PiPr3)2Cl(H)Rh(C=CC=C)Rh(H)CI(PiPr3)2] (2) in 68 % yield. In contrast to this, the corresponding reaction with the bis(trimethylsilyl) derivative Me3SiC=CC=CSiMe3 gives the mononuclear compound trans-[RhCl(eta2-Me3SiC=CC=CSiMe3)-(PiPr3)2] (3) in which one of the C=C triple bonds is uncoordinated. Photolysis of 3 in benzene solution affords quantitatively the isomeric vinylidene complex trans-[RhCl(=C=C-(SiMe3)C=CSiMe3)(PiPr3)2](4)which on hydrolysis gives trans-[RhCl(=C=CHC=CSiMe3)-(PiPr3)2] (5). The bis(vinylidene)dirhodium compound trans-[(PiPr3)2ClRh(=C=CHCH=C=)RhCl(PiPr3)2] (6) is obtained in low yield from 5 and 1 in presence of traces of water and almost quantitatively by the thermal rearrangement of 2. Both 2 and 6 react with pyridine to give [(PiPr3)2(PY)Cl(H)Rh(C=CC=C)Rh(H)Cl(py)(PiPr3)2] (7). Treatment of 1 with 1,4-dichlorobut-2-yne ClCH2C=CCH2Cl, which is the starting material for the preparation of buta-1,3-diyne, affords the butatriene rhodium(I) complex trans-[RhCl(eta2-ClHC=C=C=CH2) (PiPr3)2] (8). From 1 and hexa-1,5-diyne the dinuclear compounds[(PiPr3)2ClRh(HC=CCH2CH2C=CH)-RhCl(PiPr3)2] (9), [(PiPr3)2ClRh(=C=CHCH2CH2CH=C=)RhCl(PiPr3)2] (10), and [(Pi-Pr3)2(py)Cl(H)Rh(C=CCH2CH2C=C)Rh(H)CI(py)(PiPr3)2](11)have been prepared. The X-ray crystal structure of 3 has been determined (orthorhombic space group P2(1)2(1)2(1) (No. 19) with a = 11.19(1) angstrom, b = 15.89(2) angstrom, c = 20.75(2) angstrom, and Z = 4).