REACTIONS OF COORDINATED LIGANDS .47. SYNTHESIS, STRUCTURE, AND REACTIVITY OF (ETA-4(5E)-BUTADIENYL)RUTHENIUM COMPLEXES - CRYSTAL-STRUCTURES OF CPRU=C(PH)-ETA-3-(C(PH)C(PH)CH(PH)), CPRUC(PH)=C(PH)-ETA-2-(C(PH)=CH(PH))P(OME)3, AND CPRU2(MU-(Z)-C(PH)=CH(PH))(CO)2(ETA-4-C4PH4)

The chemistry of the first example of a η4(5e)-butadienyl complex is described. Reaction of [CpRu-(NCMe)(η4-C4Ph4)[BF4] with K[BHBus3] affords CpRu═C(Ph)-η3-(C(Ph)C(Ph)CH(Ph)) (5), which was structurally identified by single-crystal X-ray crystallography. Compound 5 is triclinic, space group P1 (No. 2); a = 10.156 (5), b = 10.996 (5), c = 13.145 (6) Å, α = 112.12 (4), β = 101.20 (4), γ = 103.76 (4)°. The molecule contains an open-chain η4(5e)-butadienyl system, in which the CpRu fragment is double bonded to C(1) (Ru–C(1) = 1.896 (5) Å), the remaining three carbon ruthenium distances Ru–C(2) (2.204 (5) Å), Ru–C(3) (2.152 (4) Å), and Ru–C(4) (2.154 (6) Å) being appropriate for an η3-allyl system. A mechanism is proposed for the formation of 5 involving conrotatory ring-opening of an η3-cyclobutenyl intermediate carrying an endo hydrogen, which becomes a pseudo-syn hydrogen on the terminus of the C4 chain. The complex 5 together with the partially characterized (Ru(PPh3)(η4-C4Ph4))x is also obtained by reacting [CpRu(PPh3)(η4-C4Ph4)][BF4] with K[BHBus3]. In contrast, the same reaction in the presence of CO or P(OMe)3 affords RuL2(PPh3)(η4-C4Ph4) (L = CO or P(OMe)3). This is rationalized in terms of the intermediacy of Ru(PPh3)(η4-C4Ph4)(η4-C5H6). In support of this the complex Ru(P(OMe)3)(η4-C4Ph4)(η4-C5H6) (9) is formed as a stable crystalline material by reaction of [CpRu(P(OMe)3)(η4-C4Ph4)][BF4] with “H-”. Thermolysis of 9 affords initially the isomeric complex CpRuC(Ph)═C(Ph)-η2-(C(Ph)═CH(Ph))P(OMe)3 (12), which is also obtained by direct reaction of 5 with P(OMe)3. The solid-state structure of 12 was established by X-ray crystallography. Compound 12 is monoclinic, space group Cc (No. 9); a = 18.226 (6), b = 12.190 (4), c = 27.447 (15) Å, α = 90, β = 94.31 (4), γ = 90°. The molecule is an η3(3e)-butadienyl complex, and significantly, along with the η4(5e) to η3(3e) transformation of the bonding mode of the butadienyl ligand, a stereomutation at C(4) has occurred on reaction of 5 with P(OMe)3. Thermolysis of 9 finally leads to the formation of a mixture of η2-bonded hexatrienyl complexes 10 and 11 formed via an apparent orthometalation reaction. Additionally the reaction of hydride anion sources with [CpRu-(CO)(η4-C4Ph4)][BF4] (1) was examined, leading to the formation of CpRu═C(Ph)-η3-(C(Ph)C(Ph)C-(CHO)Ph) (15) together with the X-ray crystallographically identified dinuclear complex CpRu2(µ-CO)(µ-(Z)-C(Ph)═CH(Ph))(CO)2(η4-C4Ph4) (16). Compound 16 is monoclinic, space group P21/c (No. 14); a = 15.763 (11), b = 15.928 (9), c = 18.914 (9) Å, α = 90, β = 112.58 (5), γ = 90°. The formation of 16 is rationalized in terms of the fragmentation of a cyclobutadiene complex. © 1990, American Chemical Society. All rights reserved.