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Ruthenium complexes containing terminal and bridging nitrido ligands

Authors Ng, Ho Yuen
Issue Date 2011
Summary Reaction of [LOEtRu(N)CI2] (1) (LOEt- = [CpCo{P(O)(OEt)2}3]- , where Cp = η5-C5H5) with Et3SiH, 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (pinacolborane) or nBu3SnH afforded the Ru(III) ammine complex [LOEtRu(NH3)CI2] (2). Treatment of 1 with [LOEtRuH(CO)(PPh3)] (3) afforded a dinuclear Ru(IV)/Ru(II) μ-imido complex [LOEtRuCI2(μ-NH)Ru(CO)(PPh3)LOEt] (4). The reaction between 1 and 3 in toluene was found to follow the rate law: rate = k2[1][3]. At 298 K, k2 was determined to be (7.2 ± 0.4) × 10-5 M-1⋅s-1. The activation parameters ΔH‡ and ΔS‡ were found to be (8.8 ± 1.6) kcal⋅mol-1 and -(43.3 ± 11.1) e.u., suggesting that the formation of 4 involved a concerted pathway of the nucleophilic attack of the nitride by the RuII hydride. Reaction of 1 with 5 atm H2 in the presence of 6 and Et3N afforded 4 and [LOEtRu(OH)(CO)(PPh3)][BF4] in 10 and 15 % yield, respectively. Reaction of 1 with [(PCy3)2RuHCl(CO)] gave the dinuclear μ-nitrido complex [LOEtRuCl2(μ-N)RuHCl(CO)(PCy3)2] (8) (Cy = cyclohexyl). A X-ray diffraction study suggested that 8 should be formulated as a RuVI≡N–RuII complex. Refluxing 1 in CCl4 afforded the mixed valence Ru(IV)/Ru(V) μ-nitrido complex [LOEtRuCl2]2(μ-N) (9), presumably via the N ⋅ ⋅ N coupling of Ru(VI) nitride and subsequent coupling of the Ru(III) intermediate with the Ru(VI) nitride. Reduction of 9 in air gave the Ru(IV)/Ru(IV) complex [H(H2O)3][LOEtRuCl2]2(μ-N) (10) that contains a symmetrical RuIV=N=RuIV bridge. 10 exhibited reversible Ru(IV,V)/Ru(IV,IV) and Ru(V,V)/Ru(IV,V) couples at 0.186 V and 1.132 V vs Cp2Fe+/0, respectively. Homo- and heterobimetallic Ru μ-nitrido complexes have been synthesized by reaction of Ru(VI) nitrides with low valent organometallic complexes. Heating 1 with [Ru(p-cymene)Cl2]2 in benzene afforded a tetranuclear Ru(IV) μ-nitrido cluster [LOEtRuCl2(μ-N)RuCl2(H2O)]2 (12) that contains a symmetrical RuIV=N=RuIV bridge. Reaction of [Ru(ppy)(MeCN)4][PF6] (Hppy = 2-phenylpyridine) with 1 afforded [LOEtRuCl2(μ-N)Ru(ppy)(MeCN)3][PF6] (13). Reaction of [Ru(ppy)(MeCN)4][PF6] with mer-[Ru(N)Cl3(AsPh3)2] and [Ru(N)Cl4]- afforded [RuCl3(AsPh3)2(μ-N)-Ru(ppy)(MeCN)3][PF6] (14) and [RuCl4(μ-N)Ru(ppy)(MeCN)3] (15), respectively. Reaction of 14 with AgOTf (OTf- = triflate) afforded [RuCl2(AsPh3)(H2O)(μ-N) Ru(ppy)(MeCN)3][PF6][OTf] (16). Substitution of 14 with K[N(Ph2PQ)2] (Q = S, O) led to formation of [Ru{N(Ph2PS)2}2Cl(μ-N)Ru(ppy)(MeCN)3][PF6] (17) and [Ru{N(Ph2PO)2}Cl2(AsPh3)(μ-N)Ru(ppy)(MeCN)3][PF6] (18), respectively. Treatment of 1 with [M(COD)Cl]2 (M = Ir, Rh COD = 1,5-cyclooctadiene) afforded Ru(VI)/M(I) heterobimetallic μ-nitrido complexes [LOEtRuCl2(μ-N)M(COD)Cl] (M = Ir (19), Rh (20)). Treatment of 1 with [Cp*IrCl2]2 (Cp* = η5-C5Me5), [Cp*Ir(ppy)(H2O)][OTf] and [Ir(ppy)2Cl]2 afforded the Ru(VI)/Ir(III) μ-nitrido complexes [LOEtRuCl2(μ-N)IrCp*Cl2] (21), [LOEtRuCl2(μ-N)IrCp*(ppy)][OTf] (22) and [LOEtRuCl2(μ-N)Ir(ppy)2Cl] (23), respectively. X-ray diffraction studies revealed that complexes 13-20 are unsymmetrical μ-nitrido complexes containing the RuVI≡N–M’ bridges. Treatment of [nBu4N][Ru(N)Cl4] with K[N(R2PS)2] in tetrahydrofuran at -78℃ afforded the Ru(IV)/Ru(IV) bimetallic μ-nitrido complexes trans-[Ru2{N(R2PS)2}4Cl(μ-N)] (R = Ph (24), Pri(25)). Reaction of [nBu4N][Ru(N)Cl4] with K[N(tBu2PS)2] gave the Ru(II) thionitrosyl complex trans-[Ru(NS){N(tBu2PS)}2Cl] (26), presumably via abstraction of the sulfur in [N(tBu2PS)2]- by a Ru(VI) nitride intermediate. Trans-[Ru(NS){N(R2PS)}2Cl] (R = Ph (29), Pri (30), tBu (26)) could be conveniently prepared from mer-[Ru(NS)Cl(AsPh3)2] and K[N(R2PS)2]. Treatment of [Ru(PPh3){N(Ph2PS)2}2] with PhN3 afforded [Ru{N(PhN)}2{N(Ph2PS)2}2] (32) containing a neutral tetrazene ligand, presumably via the [2+3] cycloadditon of a Ru(IV)=NPh intermediate with PhN3. A cationic Ru(VI) nitride complex containing a bulky bidentate Schiff base ligand, trans-[Ru(N)(H2O)L2][OTf] (34), was prepared from cis-[Ru(N)Cl(L)2] (33) (HL = 2-[(2,6-diisopropylphenyl)imino]methyl-4,6-dibromophenol) and AgOTf. No N ⋅ ⋅ N coupling was found when 34 was reacted with pyridine in polar solvents. Treatment of 33 with Me3NO and elemental sulfur gave cis-[Ru(NO)Cl(L)2] (35) and cis-[Ru(NS)Cl(L)2] (36), respectively. Irradiation of cis-[Ru(NO)Cl(L)2] in CH2Cl2/MeCN with UV ligand afforded [Ru(MeCN)Cl(L)2] (37) that could also be prepared by treatment of 33 with Me3SiN3. Refluxing FeCl2 with HL in methanol in the presence of Et3N afforded [Fe(OMe)(L)2] (38). Reaction of [Fe(OMe)(L)2] with HCl and Me3SiN3 gave [FeCl(L)2] (39) and [Fe(N3)L2] (40), respectively.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2011
Language English
Format Thesis
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