Issue 2, 1979

Pentamethylcyclopentadienyl-rhodium and -iridium complexes. Part 21. Neutral and cationic β-diketonato-, η3-allylic, and NN″-triazenido-complexes: the X-ray crystal structure of the binuclear complex [Rh2(C5Me5)2(acac)2][BF4]2

Abstract

The synthesis and properties of the (β-diketonato-complexes [M(η5-C5Me5)X(R1COCHCOR2)][M = Rh, X = Cl, R1= R2= Me, R1= R2= CF3, R1= Me, R2= Prn, R1= Me, R2= OEt, or R1= Me, R2= CF3; M = Rh, R1= R2= Me, X = Br, I, N3, or OAc (acetate); and M = Ir, X = Cl, R1= R2= Me, or R1= R2= CF3] obtained from [M25-C5Me5)2Cl4][M = Rh (1a) or Ir (1b)] and Na[R1COCHCOR2] are reported. Iridium forms a stable complex [Ir(η5-C5Me5)(acac)2] in which the two acac (MeCOCHCOMe) groups are OO′- and C-bonded respectively; no exchange is detectable on the 1H n.m.r. time scale. The complex [Rh(η5-C5Me5)Cl(acac)] undergoes substitution when treated with N-bromo- or N-iodo-succinimide to give [Rh(η5-C5MC5)Cl(MeCOCYCOMe)](Y = Br or I). Reaction of [Rh(η5-C5Me5)Cl(MeCOCHCOR2)] with AgX gives binuclear [Rh25-C5Me5)2(MeCOCHCOR2)2][X]2(R2= Me, Prn, or OEt; X = PF6 or BF4). The complex [Rh25-C5Me5)2(acac)2][BF4]2(14a) has been shown by X-ray crystallography to contain two bridging acac ligands. OO′-bonded to one rhodium and C-bonded to the other. A major contributor to the structure of the acac ligand is the β-diketone form, although a delocalised β-diketonate form also plays an important role. The η5-C5Me5 ring in (14a) is distorted towards an ‘ene-enyl’ structure, the shortest C[graphic omitted]C (‘ene’) bond being trans to the Rh–C(acac)σ-bond. Reaction of [Rh25-C5Me5)2(acac)2][PF6]2 with L gives [Rh(η5-C5Me5)L(acac)][PF6][L = PPh3, P(OEt)3, ButNC, py, NH2Me, or NHMe2]; similarly prepared are [Rh(η5-C5Me5)L(CF3COCHCOCF3)][PF6](L = MeCN or PPh3). Reaction of (1a) with RNHN[double bond, length half m-dash]NR and base or Ag[N3R2] gives the NN″-bonded triazenido-complexes [Rh(η5-C5Me5)Cl(N3R2)](R = Ph, p-MeC5H4, or p-ClC5H4); the NN′-bonded acetamidinato-complex [Rh-(η5-C5Me5)Cl(PhNCMeNPh)] is prepared similarly. On reaction with L in the presence of Ag[PF6] these give [Rh(η5-C5Me5)L(RNXNR)][PF6][X = N, R = Ph, L = MeCN or P(OMe)3; X = CMe, R = Ph, L = MeCN or PPh3. The azido-complex [Rh25-C5Me5)2(N3)4] forms adducts [Rh25-C5Me5){N3)4(RNHN[double bond, length half m-dash]NR)] with RNHN[double bond, length half m-dash]NR (R = Ph or p-MeC6H4). The η3-1-methylallyl complex [Rh(η5-C5Me5)(η3-1-MeC3H4)Cl] also forms the cationic complexes [Rh(η5-C5Me5)(η3-1-MeC3H4)L][PF6][L = MeCN, P(OMe)3, PPh3, or NH2Et] on reaction with L in the presence of Ag[PF6].

Article information

Article type
Paper

J. Chem. Soc., Dalton Trans., 1979, 387-394

Pentamethylcyclopentadienyl-rhodium and -iridium complexes. Part 21. Neutral and cationic β-diketonato-, η3-allylic, and NN″-triazenido-complexes: the X-ray crystal structure of the binuclear complex [Rh2(C5Me5)2(acac)2][BF4]2

W. Rigby, H. Lee, P. M. Bailey, J. A. McCleverty and P. M. Maitlis, J. Chem. Soc., Dalton Trans., 1979, 387 DOI: 10.1039/DT9790000387

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