1‐Dodecene Hydroformylation Catalyzed by Water Soluble Rhodium Phosphine Complex in Two‐Phase System

1‐Dodecene hydroformylation catalyzed by water soluble rhodium complex [RhCl(CO) (TPPTS)₂] was studied in the presence of TTPTS [P(m‐C₂H₄SO₃Na)₃] and CTAB (cetyltrimethyl ammonium). The influence of reaction parameters was discussed in detail based on micelle effect in biphasic system. The modification for the microcircumstance of micelle interface was conducted by the introduction of a catalyst promoter TPPDS [PhP(m‐C₂H₄SO₃Na)₂] into the reaction solution. A synergistic effect between TPPDS and TPPTS on the regioselectivity of 1‐dodecene hydroformylation was observed. The selectivity of linear aldehyde in the products was so high as 95.7% at the molar ratio of [TPPDS]/[TPPTS] = 0.5.     

Rhodium-catalyzed hydroformylation of C6 alkenes and alkene mixtures - a comparative study in homogeneous and aqueous-biphasic media using PPh3, TPPTS and TPPMS ligands

The complexes RhH(CO)L₃, where L = PPh₃, P(m-C₆H₄SO₃Na)₃ (TPPTS), and (C₆H₅)₂P(m-C₆H₄SO₃Na) (TPPMS) were used as catalyst precursors for a comparative study of the catalytic hydroformylation of several C6 alkenes and alkene mixtures under moderate reaction conditions in homogeneous (PPh₃) and aqueous-biphasic (TPPTS, TPPMS) media. The biphasic systems are efficient for the hydroformylation of hex-1-ene, 2,3-dimethyl-1-butene, styrene, cyclohexene, and mixtures thereof, in water/n-heptane at 80 °C. The main problem associated with these catalysts is their tendency to promote alkene isomerization if the effective syngas concentration in the liquid phases is low, but this side-reaction can be suppressed by using higher CO/H₂ pressures (54 atm). The selectivity of both water-soluble catalysts for linear products of hex-1-ene and for branched products of styrene is modest in comparison with the homogeneous system, which may limit their utility for classical oxo uses, but this is not a disadvantage for other interesting applications related to the hydroformylation of alkene mixtures and particularly to naphtha upgrading where linear and branched products are equally useful. The catalysts can be recycled without significant loss of activity and are resistant to the presence of benzothiophene in the mixture.     

Chemistry of oxovanadium(IV) bound to tetradentate ONNO donors: Influence of axial coordination on the V-O(1)bond

Chelating behaviour of some tetradenate ONNO donors derived fromq - aminobenzoylhydrazide and some diketones toward oxo-vanadium(IV) ion is reported. The donors react with oxometal cation depending on the pH of the reaction medium. The product containing the neutral keto and the binegative enol form of the donors have the formulae [VO(H₂L)(SO₄)] (at pH 3.0)(┘1) and [VO(L)(H₂O)] (at pH 6.0)(┘2) respectively [H₂L = (2-NH₂)C₆H₄CONH: C(R) (CH₂)_mC(R): NNH CO C₆H₄(2−NH₂); H₂L = H₂DA(R= CH₃,m = 0), H₂BA(R = C₆H₅,m = 0), H₂AA(R = CH₃,m = 2)]. Both (┘1) and (┘2) react with a neutral monodentate donor B(B = pyridine, aniline etc.) yielding mixed-ligand complexes [VO(L)(B)]. Influence of the axial coordination on the V-O₍₁₎ bond is discussed and a monomeric distorted octahedral donor environment for the oxovanadium(IV) ion has been suggested     

水/有机两相体系1-癸烯氢氨甲基化反应中TPPTS和TPPDS的协同效应

 在 RhCl(CO)(TPPTS)2-TPPTS[P(m-C6H4SO3Na)3]/TPPDS[C6H5P(m-C6H4 SO3Na)2]-CTAB (十六烷基三甲基溴化铵) 水-有机两相催化体系中, 系统考察了 TPPTS/TPPDS 摩尔比、反应压力、阳离子表面活性剂结构及其浓度对 1-癸烯氢氨甲基化反应区域选择性的影响. 结果表明, TPPDS 的加入对生成胺的区域选择性的影响非常大. 当 TPPTS/TPPDS 摩尔比为 4 时, 直链胺和支链胺之比由不加 TPPDS 时的 8.2 增加到 21.0. 可见, TPPTS 和 TPPDS 存在着明显的协同效应. 阳离子表面活性剂的结构对生成胺的区域选择性影响也很大, 加入双长链阳离子表面活性剂时区域选择性远低于单长链阳离子表面活性剂, 且形成的聚集体越紧密, 越有利于提高产物正/异比.     

Olefin complexes of rhodium(I) containing the ligands but-3-enyldiphenylphosphine and diphenylpent-4-enylphosphine

But-3-enyldiphenylphosphine (mbp) and diphenylpent-4-enylphosphine (mpp) react with Rh₂Cl₂(C₂H₄)₄ (molar ratio $\text{2}\text{1}$ to form the four coordinate dimeric complexes Rh₂Cl₂(mbp)₂ and Rh₂Cl₂(mpp)₂ respectively, while but-3-enyldiphenylphosphine reacts with Rh₂Cl₂(C₂H₄)₄ (molar ratio $\text{4}\text{1}$) to form RhCl(mbp)₂, a five coordinate complex in the solid state. The dimers further react with sodium tetraphenylborate to give the π-bonded tetraphenylborate complexes Rh[mbp][C₆H₅)₄B] and Rh[i-mpp][(C₆H₅)₄B] where i-mpp = (C₆H₅)₂P(CH₂CH₂CHCHCH₃). RhCl(CO)(mbp)₂ reacts with sodium tetraphenylborate to form the five coordinate cationic complex [Rh(CO)(mbp)₂][(C₆H₅)₄B]. Both RhCl(CO)(mbp)₂ and RhCl(mbp)₂ react with hydrogen in methanol saturating the olefin to form RhCl[CO][(C₆H₅)₂P(C₄H₉)]₂ and Rh₂Cl₂[(C₆H₅)₂P(C₄H₉)]₂ respectively.     

Study of hydroformylation of formaldehyde in the presence of rhodium catalysts byin situ IR spectroscopy and the kinetic technique

Carbonylrhodium complexes formed during hydroformylation of CH₂O from various rhodium precursors were investigated byin situ IR spectroscopy. It was found that under the conditions of the hydroformylation of CH₂O inN,N-dimethylacetamide (DMAA), RhH(CO)(PPh₃)₃, RhCl(CO)(PPh₃)₂, RhCl(PPh₃)₃, RhCl(CO)(PBu₃)₂, and [RhCl(CO)₂]₂ form complex systems that necessarily contain anionic complexes, [Rh(CO)₂L_x(DMAA)_y]^– (L = PPh₃, PBu₃,x = 1 to 2,y = 1 to 0; [Rh(CO)₄]^–). The participation of ionic structures in the hydroformylation of CH₂O, most likely, in the step of the activation of CH₂O, was proven by kinetic techniques.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1066–1069, June, 1995.     

阳离子表面活性剂存在下水/有机两相体系中双环戊二烯氢甲酰化

研究了在阳离子表面活性剂存在下水/有机两相中水溶性铑配合物RhCI(CO)(TPPTS)2(TPPTS:P(m-C6H4SO3Na)3)催化双环戊二烯氢甲酰化反应,考察了反应温度、催化剂浓度、不同水溶性膦配体TPPTS和TPPDS(C5H5P(m-C6H4SO3Na)2),以及表面活性剂结构对催化反应的影响.结果表明,...     

Ferrocenyl-nitrogen donor ligands. Synthesis and characterization of rhodium(I) complexes of ferrocenylpyridine and related ligands

The preparation of a series of complexes of the types [RhCl(CO)₂(L)], [RhCl(cod)(L)] and [Rh(cod)(L)₂]ClO₄, where L is a ligand incorporating a ferrocenyl group and a pyridine ring is described. Complexes were characterized using NMR, IR and electronic spectroscopy. The electrochemical behaviour of the complexes was examined using cyclic voltammetry. The X-ray structures of three of the complexes, [RhCl(CO)₂{NC₅H₄CNC₆H₄(η⁵-C₅H₄)Fe(η⁵-C₅H₅)}], [RhCl(cod)(3-Fcpy)] and [RhCl(cod){3-Fc(C₆H₄)py}], were determined.     

Mono-Sulfonated Derivatives of Triphenylphosphine, [NH4]TPPMS and M(TPPMS)2 (TPPMS = P(Ph)2(m-C6H4SO− 3); M = Mn2+, Fe2+, Co2+ and Ni2+). Crystal Structure Determinations for [NH4][TPPMS]·½H2O, [Fe(H2O)5(TPPMS)]TPPMS, [Co(H2O)5TPPMS]TPPMS and [Ni(H2O)6](TPPMS)4·H2O

Preparation of the ammonium salt of TPPMS, [NH₄]TPPMS, TPPMS = PPh₂(m-C₆H₄SO^? ₃), greatly enhances water solubility and provides an efficient route to other metal complexes of TPPMS, M(TPPMS)₂ M = Mn²⁺, Co²⁺, Fe²⁺ and Ni²⁺. For Co²⁺ and Fe²⁺ the metal has an octahedral ligand environment with five water molecules and one TPPMS coordinated through the sulfonate oxygen; the second TPPMS is not coordinated. For Ni²⁺ the octahedral coordination sphere is composed of water molecules and the TPPMS ligands are not coordinated. Structures are fully reported for [NH₄]TPPMS·½H₂O and [Fe(H₂O)₅(TPPMS)]TPPMS and partially reported for [Co(H₂O)₅TPPMS]TPPMS and [Ni(H₂O)₆]TPPMS₂·H₂O. All of the structures show hydrophobic regions consisting of aromatic rings and hydrophilic regions with hydrogen-bonding interactions.     

Syntheses and Structures of Homo‐ and Heterobimetallic Complexes Containing a (Cyclopentadienone)rhodium(I) Fragment

The reaction of [RhCl(η⁴‐Ph₂R₂C₄CO)]₂ (R=Ph, 2‐naphthyl) with the dimeric complexes [RuCl₂(p‐cymene)]₂ p‐cymene=1‐methyl‐4‐(1‐methylethyl)benzene, [RuCl₂(1,3,5‐Et₃C₆H₃)]₂, [MCl₂(Cp*)]₂ (M=Rh, Ir; Cp*=1,2,3,4,5‐pentamethylcyclopenta‐2,4‐dien‐1‐yl), [RuCl₂(CO)₃]₂, [RuCl₂(dcypb)(CO)]₂ (dcypb=butane‐1,4‐diylbis[dicyclohexylphosphine]), [(dppb)ClRu(μ‐Cl)₂(μ‐OH₂)RuCl(dppb)] (dppb=butane‐1,4‐diylbis[diphenylphosphine]), and [(dcypb)(N₂)Ru(μ‐Cl)₃RuCl(dcypb)] was investigated. In all cases, mixed, chloro‐bridged complexes were formed in quantitative yield (see 5 – 8, 9 – 16, 18, 19, 21 , and 22 ). The six new complexes 5, 8, 9, 13, 15 , and 22 were characterized by single‐crystal X‐ray analysis (Figs. 1–3).     

Hydrogenation of Aromatics with [Ru(η 5-C5H5)Cl(TPPDS)2] in Biphasic Medium

[Ru(η⁵-C₅H₅)Cl(TPPDS)₂], [TPPDS=P(C₆H₅)(C₆H₄SO₃⁻)₂] in biphasic (n-heptane/water) medium hydrogenates toluene, benzene and m-xylene (105 °C, 1400 psig H₂, substrate/catalyst=600:1, 4 h) and in toluene hydrogenation gives methylcyclohexane. Catalytic activity increases with temperature, H₂ pressure, ionic strength, and pH lower than 10. The catalytic water solution can be reused several times with little activity loss.     

Electron‐Rich Diferrous–Phosphane–Thiolates Relevant to Fe‐only Hydrogenase: Is Cyanide “Nature's Trimethylphosphane”?

The two‐step one‐pot oxidative decarbonylation of [Fe₂(S₂C₂H₄)(CO)₄(PMe₃)₂] ( 1 ) with [FeCp₂]PF₆, followed by addition of phosphane ligands, led to a series of diferrous dithiolato carbonyls 2 – 6 , containing three or four phosphane ligands. In situ measurements indicate efficient formation of 1 ²⁺ as the initial intermediate of the oxidation of 1 , even when a deficiency of the oxidant was employed. Subsequent addition of PR₃ gave rise to [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₃(PMe₃)₃]²⁺ ( 2 ) and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₂(PMe₃)₂(PR₃)₂]²⁺ (R=Me 3 , OMe 4 ) as principal products. One terminal CO ligand in these complexes was readily substituted by MeCN, and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₂(PMe₃)₃(MeCN)]²⁺ ( 5 ) and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)(PMe₃)₄(MeCN)]²⁺ ( 6 ) were fully characterized. Relevant to the H_red state of the active site of Fe‐only hydrogenases, the unsymmetrical derivatives 5 and 6 feature a semibridging CO ligand trans to a labile coordination site.     

Cationic arenechromium-nitrosyls and -hydrides

Complexes Cr(CO)₂L(C₆Me_6-nH_n), n = 0-3, L = CO and PPh₃, react with NOPF₆ in methanol/toluene to give [Cr(CO)L(NO)(C₆Me_6-nH_n)] PF₆, n = 0-3, L = CO; n = 0, L = PPh₃, and these react with nucleophiles (X^-) to give cyclohexadienyl derivatives Cr(CO)₂(NO)(C₆Me_6-nH_nX); the compounds Cr(CO)₂(PhCCPh)(C₆Me_6-nH_n) react with NOPF₆ to yield [Cr(H)(CO)₂(PhCCPh)(C₆Me_6-nH_n)] PF₆, n = 0 and 1.     

Seven-coordinate complexes of molybdenum(II) and tungsten(II) containing pyrazole as a ligand

Summary Equimolar quantities of [MI₂(CO)₃(NCMe)₂] (M = Mo or W) and C₃H₄N² (pyrazole) react in CH₂C1₂ at room temperature to give the iodo-bridged dimers [M(μ-I) (CO)₃(C₃H₄N²)]₂ (1) and (2). Two equivalents of C₃H₄N² react with [MI₂(CO)₃(NCMe)₂] (M = Mo or W) to give the bis(pyrazole) complexes [MI₂(CO)₃(C₃H₄N²)₂] (3) and (4) in good yield. Three and four equivalents of pyrazole react with [MoI₂(CO)₃(NCMe)₂] to give the cationic complexes [MoI(CO)₃(C₃H₄N²)₃]I (5) and [MoI(CO)₂(C₃H₄N²)₄]I (6), respectively. The mixed ligand complexes [MI₂(CO)₃(C₃H₄N²)L] (M = Mo or W; L = PPh₃, AsPh₃ or SbPh₃) (7)-(12) are prepared by reacting equimolar amounts of [MI₂(CO)₃(NCMe)₂] and L in CH₂C1₂ at room temperature, followed by an in situ reaction with one equivalent of C₃H₄N². The MoSnCl₃ complex [MoCl(SnCl₃)(CO)₃(C₃H₄N²)₂] (13) is prepared in an analogous manner using acetone as the solvent, whilst the mixed ligand compound [MoCl(SnQ₃)(CO) ₃(C₃H₄N²)(PPh₃)] (14) was prepared by treating the dimeric complex [Mo(μ-Cl)(SnCl₃)(CO)₃(PPh₃)]₂ with two equivalents of C₃H₄N². All the new complexes were characterised by elemental analysis (carbon, hydrogen and nitrogen), i.r. and ¹H n.m.r. spectroscopy.     

Pseudohalogenometallverbindungen: LVIII. Reaktionen von diphenylphosphorylazid und perfluor-n-hexylsulfonylazid mit triphenylphosphan-komplexen von platin(0), rhodium(I), iridium(I), ruthenium(0), kobalt(II) und kupfer(I)

Diphenylphosphorylazide N₃P(O)(OPh)₂ reacts with Pt(PPh₃)₃, Pt(PPh₃)₂(C₂H₄), trans-RhCl(CO)(PPh₃)₂, Ru(CO)₃(PPh₃)₂, CoCl₂(PPh₃)₂ and CuCl(PPh₃)₂ to give the azido complexes Pt(PPh₃)₂(N₃)R, Pt(PPh₃)₂(N₃)₂R₂, the urylene complex RhCl(PPh₃)₂(RNCONR) and the phosphine imine complexes Ru(CO)₃(RPPh₃)₂, CoCl₂(RNPPh₃)₂, CuCl(RNPPh₃)₂, respectively, (RP(O)(OPh)₂). The oxidative addition of n-C₆F₁₃SO₂N₃ to Pt(PPh₃)₄ and Pt(PPh₃)₂(C₂H₄) affords the complexes Pt(PPh₃)₂(N₃)R and Pt(PPh₃)₂(N₃)₂R₂, respectively, (RSO₂C₆F₁₃. The compounds are characterized by elemental analysis and by their IR spectra.     

Reactions involving transition metals: XX. A comparison of the reactions of 1,2,3,4,7,7-hexafluorobicyclo[2.2.1]heptadiene,and 2,3-bis(trimethyltin)- and 2,3-dichloro-1,4,5,6,7,7-hexafluorobicyclo[2.2.1]hepta-2,5-dienes with low valent transition metal complexes

1,2,3,4,7,7-Hexafluorobicyclo[2.2.1]heptadiene (1) and 2,3-bis(trimethyltin)-1,4,5,6,7,7-hexafluorobicyclo[2.2.1]hepta-2,5-diene (2) react with [M(Ph₃P)₄] (M = Pt, Pd) to afford air-stable adducts. 2,3-Dichloro-1,4,5,6,7,7-hexafluorobicyclo[2.2.1]hepta-2,5-diene (3) gives only [PtCl₂(PPh₃)₂] with [Pt(Ph₃P)₄], but a low yield of an adduct was obtained with [Pd(PPh₃)₄]. The diene 1 also reacts with Fe(CO)₅ to form the complex [(C₇H₂F₆)Fe(CO)₄], and with [Rh(C₂H₄)₂(acac)] to give [(C₇H₂F₆)Rh(acac)] in which the diene acts as a bidentate ligand. Similar products could not be isolated from the reactions of 2 and 3. A stable adduct, believed to be [{C₇F₆(SnMe₃)₂}Rh(CO)₂(μ-Cl)₂Rh(CO)₂] has been isolated from the reaction between 2 and [Rh(CO)₂Cl]₂. This adduct reacts with PPh₃ to give the bridge-cleavage product [{C₇F₆(SnMe₃)₂}RhCl(CO)(PPh₃)₂]. Reaction of 1 with [Rh(CO)₂Cl]₂ gives an unstable adduct which could not be isolated, and 2 does not react at room temperature. The chloro derivative 3 reacts with [PdCl₂(PhCN)₂] to give the adduct [(C₇F₆Cl₂)PdCl(PhCN)], but 1 and 2 do not react under similar conditions. Stable substitution products [(C₇F₆R₂)M] (R = H, M = Fe(CO)₂(η-C₅H₅); R = SnMe₃, M = Fe(CO)₂(η-C₅H₅), Mn(CO)₅, Ir(CO)₂(PPh₃)₂, Rh(CO)₂(PPh₃)₂; R = Cl, M = Ir(CO)₂(PPh₃)₂, Rh(CO)₂(PPh₃)₂) have been isolated from the reactions of the dienes with carbonylmetal anions. Insertion of the CHCH bond occurs when 1 is heated with [MnMe(CO)₅] to give [{C₇F₆H₂C($\text{O)Me}M}$n(CO)₄], and this, on reaction with either PPh₃ or [Pt(PPh₃)₄], gives [(C₇F₆H₂COMe)Mn(CO)₄PPh₃].     

Synthesis and Characterization of New Water‐Soluble Hydrides of RuII: A Step towards Dinitrogen Activation?

The basic aqueous coordination chemistry of Ru^II has been studied using the catalytically important TPPTS phosphine (TPPTS=trisodium salt of 3,3′,3″‐phosphinetriylbenzenesulfonic acid) and small gas molecules (H₂, CO, N₂) as ligands. As a result, new water‐soluble ruthenium mixed hydride complexes, presumably key species in many industrial catalytic processes, have been formed and identified. The Ru^II mixed hydrides were synthesized, and their formation was followed in situ by multinuclear NMR spectroscopy, pressurizing aqueous Ru^II? TPPTS systems with H₂ and CO gas in sapphire NMR tubes. The formation equilibrium of these complexes is highly dependant on the temperature and the gas pressures. Under 50 atm of N₂, the unique [RuH(CO)(N₂)(TPPTS)₂(H₂O)]⁺ complex has been identified, which could be the first step toward dinitrogen activation.     

Facile Synthesis and Versatile Reactivity of an Unusual Cyclometalated Rhodium(I) Pincer Complex

The synthesis of the reactive PN(C^H) ligand 2‐di(tert‐butylphosphanomethyl)‐6‐phenylpyridine ( 1^H ) and its versatile coordination to a Rh^I center is described. Facile C?H activation occurs in the presence of a (internal) base, thus resulting in the new cyclometalated complex [Rh^I(CO)(κ³‐P,N,C‐ 1 )] ( 3 ), which has been structurally characterized. The resulting tridentate ligand framework was experimentally and computationally shown to display dual‐site proton‐responsive reactivity, including reversible cyclometalation. This feature was probed by selective H/D exchange with [D₁]formic acid. The addition of HBF₄ to 3 leads to rapid net protonolysis of the Rh?C bond to produce [Rh^I(CO)(κ³‐P,N,(C?H)‐ 1 )] ( 4 ). This species features a rare aryl C?H agostic interaction in the solid state, as shown by X‐ray diffraction studies. The nature of this interaction was also studied computationally. Reaction of 3 with methyl iodide results in rapid and selective ortho‐methylation of the phenyl ring, thus generating [Rh^I(CO)(κ²‐P,N‐ 1^Me )] ( 5 ). Variable‐temperature NMR spectroscopy indicates the involvement of a Rh^III intermediate through formal oxidative addition to give trans‐[Rh^III(CH₃)(CO)(I)(κ³‐P,N,C‐ 1 )] prior to C?C reductive elimination. The Rh^III–trans‐diiodide complex [Rh^I(CO)(I)₂(κ³‐P,N,C‐ 1 )] ( 6 ) has been structurally characterized as a model compound for this elusive intermediate.     

Pyridine-2-olato chelated ruthenium(II) organometallics incorporating imine-phenol function: spectroscopic,structural, electrochemical,and theoretical studies

The heterogeneous phase reaction of excess sodium salt of 2-hydroxypyridine (OHpy) with [Ru(κ²C,O-RL)(PPh₃)₂(CO)Cl] (1) afforded complexes of the type [Ru(κ¹C-RL)(PPh₃)₂(CO)(Opy)] (2) in excellent yield [κ²C,O-RL is 4-methyl-6-((N-R-arylimino)methyl)phenolato-C²,O), κ¹C-RL is 4-methyl-6-((N-R-arylimino)methyl)phenol-C²) and R is H, Me, OMe, Cl]. The chelation of Opy is attended with the cleavage of Ru-O and Ru-Cl bonds and iminium-phenolato → imine-phenol prototropic shift. The 1→2 conversion is irreversible and the type 2 species are thermodynamically more stable than the acetate, nitrite, and nitrate complexes of 1. The spectral (UV-vis, IR, NMR) and electrochemical data of the complexes are reported. In dichloromethane solution the complexes display one quasi-reversible Ru^III/Ru^II cyclic voltammetric response with E_1/2 in the range 0.65–0.69 V versus Ag/AgCl. The crystal and molecular structures of [Ru(κ¹C-HL)(PPh₃)₂(CO)(Opy)]·2C₆H₆·0.5H₂O, 2(H)·2C₆H₆·0.5H₂O and [Ru(κ¹C-ClL)(PPh₃)₂(CO)(Opy)]·2C₆H₆·0.25H₂O, 2(Cl)·2C₆H₆·0.25H₂O are reported, which revealed a distorted octahedral RuC₂P₂NO coordination sphere. The pairs (P,P), (C,O), and (C,N) define the three trans directions. The electronic structures of the complexes are also scrutinized by density functional theory.     

A rhodium(I) derivative of diethyl(diphenylphosphinomethyl)amine as a ligand for the synthesis of homo- and hetero-dinuclear complexes

The reaction of [Rh(μ-Cl)(CO)(C₂H₄)]₂ with diethyl(diphenylphosphinomethyl)amine (ddpa)(1:4) yields RhCl(CO)(ddpa)₂, a mononuclear complex able to act as ligand towards a second metal through its uncoordinated nitrogen atom. Two examples are described, namely the reaction with [Rh(μ-Cl)(CO)₂]₂ leading to Rh₂(μ-Cl)Cl(μ-CO)(CO)(μ-ddpa)₂ and that with PdCl₂(COD)(COD = 1,5-cyclooctadiene) to PdRh(μ-Cl)Cl₂(CO)(μ-dppa)₂. In both homo- and hetero-dinuclear complexes, the ligand is thought to retain a head-to-head arrangement.