Heterotrinuclear Complexes with Palladium, Rhodium, and Iridium Ions Assembled by Conformational Switching of a Tetraphosphine Ligand around a Palladium Center

Abstract

Reaction of [PdCl 2 (cod)] with a tetraphosphine, meso-bis[((diphenylphosphino)methyl)phenylphosphino]methane (dpmppm), afforded the mononuclear Pd II complexes [PdCl(dpmppm-κ 3 )]X (X = Cl (1a), PF 6 (1b)); the pincer-type dpmppm ligand coordinates to the Pd atom with two outer and one inner phosphorus atom to form fused six-and four-membered chelate rings. The remaining inner phosphine is uncoordinated and readily reacts with [Cp*MCl 2 ] 2 to give the heterodimetallic complexes [PdCl-(Cp*MCl 2 )(μ-dpmppm-κ 3 ,κ 1 )]X (X = Cl, M = Rh (21a), Ir (21b); X = PF 6 , M = Rh (23a), Ir (23b)). Attachment of the second metal fragment to the uncoordinated phosphine caused a crucial conformational change of the six-membered chelate ring from a stable chair conformation to a twist-boat structure, which concomitantly destabilizes the four-membered ring for its opening reactions. Complexes 21 (X = Cl) were converted to [PdCl 2 (Cp*MCl 2 )(dpmppmO)], in which the terminal P atom is dissociated and oxidized as Ph 2 P(O)CH 2 P(Ph)CH 2 P(Ph)CH 2 PPh 2 (dpmppmO), and in the presence of another 1 equiv of [Cp*M′Cl 2 ] 2 , complexes 21 were readily transformed into the heterotrinuclear complexes [PdCl 2 (Cp*M′Cl 2 )(Cp*MCl 2 )(μdpmppm-κ 2 ,κ 1 ,κ 1 )] (M = M′ = Rh (31a), Ir, (31b); M = Ir, M′ = Rh (31c)), where the third metal M′ is trapped by the terminal P atom with its four-membered-ring opening. Complexes 23 also reacted with another 1 equiv of [Cp*M′Cl 2 ] 2 to afford the heterotrinuclear complexes [PdCl(μ-Cl)(Cp*M′Cl)(Cp*MCl 2 )(μ-dpmppm-κ 2 ,κ 1 ,κ 1 )]PF 6 (M = M′ = Rh (32a), Ir, (32b); M = Ir, M′ = Rh (32c), M = Rh, M′ = Ir (32d)); the additional metal M′ is ligated by the terminal phosphine and is further connected to the Pd atom via a chloride bridge, resulting in a rather electron-deficient M′ center on the basis of cyclic voltammetry. These results exhibited that the addition of a bulky metal fragment to the uncoordinated phosphine of 1 brings about a conformational switch around the Pd center to promote the ring-opening reaction of the four-membered chelate ring, which leads to an incorporation of the third metal fragment to construct heterotrinuclear structures.

Gold and Silver Chains Supported by Linear Hexaphosphine Ligands

“…In contrast to the higher nuclearity systems, dpmppm also provides a scaffold for a hydride‐bridged dicopper(I) center, [Cu 2 (μ‐H)(μ‐ meso ‐dpmppm) 2 ]X (X=BF 4 , PF 6 ), which undergoes insertion of CO 2 under mild conditions to yield a formate‐bridged dicopper complex, [Cu 2 (μ‐HCO 2 )(μ‐ meso ‐dpmppm) 2 ]X . The versatile coordination behavior of meso ‐dpmppm further organized stepwise assemblies of heterotrinuclear metal ions of PdMM′ systems (M, M′=Rh, Ir) . These recent results from our group clearly suggested that the linear polyphosphines are potentially useful to create diverse multinuclear metal arrays.…”

Dinuclear Copper Complexes Triply Bridged by a Tetraphosphane, rac‐Ph2PCH2P(Ph)CH2P(Ph)CH2PPh2

“…Multinuclear transition‐metal complexes have extensively been studied to explore new aspects of functional materials because a variety of synergistic effects in multimetallic centers are expected to play key roles in developing catalytic systems, electronic, optical, and magnetic devices, and biomimetic functional molecules . To create desired multinuclear centers, design of multidentate metal supporting ligands is very important issue, and in this regard, we have prepared a methylene‐bridged linear tetraphosphane, meso ‐ and rac ‐bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), and demonstrated that it effectively stabilized versatile tetra‐, tri‐, and dinuclear homo and heterometallic systems as well as mononuclear centers (Scheme ) . First of all, meso ‐ and rac ‐dpmppm preferably supported linearly ordered tetranuclear metal centers in κ 1 ,κ 1 ,κ 1 ,κ 1 coordination mode (Scheme a, Scheme f), exemplified by the linear octapalladium rigid‐rods, [Pd 8 ( meso ‐ or rac ‐dpmppm) 4 L 2 ] 4+ (L = none, MeCN, N , N ‐dimethylformamide (dmf), and isocyanides),, which dissociate at higher temperature T > 100 °C into two tetrapalladium units of {Pd 4 ( meso ‐ or rac ‐dpmppm) 2 } 2+ and interestingly they are self‐aligned at lower temperature T < 60 °C to restore the original rods through asymmetric recognition between the tetrapalladium units .…”

“…The meso ‐dpmppm ligand was found to surround a Pd II or Pt II mononuclear center in a pincer‐type κ 3 ‐fashion (Scheme e) affording [MCl(dpmppm‐κ 3 )] + (M = Pt, Pd) that involve fused six‐ and four‐membered chelate rings with an uncoordinated phosphane unit in the six‐membered ring, and are transformed, by addition of Cp*MCl 2 fragment (M = Rh, Ir) onto the uncoordinated phosphane, into [MCl(Cp*M′Cl 2 )(µ‐ meso ‐dpmppm‐κ 3 ,κ 1 )] + (M = Pt, Pd; M′ = Rh, Ir) (Scheme d) , . The PdM′ complex with meso ‐dpmppm‐κ 3 ,κ 1 bridge captured the third metal ion via cleavage of the four‐membered chelate ring to afford heterotrimetallic complexes, [PdCl 2 (Cp*M′Cl 2 )(Cp*MCl 2 )(µ‐ meso ‐dpmppm‐κ 2 ,κ 1 ,κ 1 )] and [PdCl(µ‐Cl)(Cp*M′Cl)(Cp*MCl 2 )(µ‐dpmppm‐κ 2 ,κ 1 ,κ 1 )]PF 6 (M, M′ = Rh, Ir), in stepwise ways (Scheme b) .…”

“…The meso ‐dpmppm ligand was found to surround a Pd II or Pt II mononuclear center in a pincer‐type κ 3 ‐fashion (Scheme e) affording [MCl(dpmppm‐κ 3 )] + (M = Pt, Pd) that involve fused six‐ and four‐membered chelate rings with an uncoordinated phosphane unit in the six‐membered ring, and are transformed, by addition of Cp*MCl 2 fragment (M = Rh, Ir) onto the uncoordinated phosphane, into [MCl(Cp*M′Cl 2 )(µ‐ meso ‐dpmppm‐κ 3 ,κ 1 )] + (M = Pt, Pd; M′ = Rh, Ir) (Scheme d) , . The PdM′ complex with meso ‐dpmppm‐κ 3 ,κ 1 bridge captured the third metal ion via cleavage of the four‐membered chelate ring to afford heterotrimetallic complexes, [PdCl 2 (Cp*M′Cl 2 )(Cp*MCl 2 )(µ‐ meso ‐dpmppm‐κ 2 ,κ 1 ,κ 1 )] and [PdCl(µ‐Cl)(Cp*M′Cl)(Cp*MCl 2 )(µ‐dpmppm‐κ 2 ,κ 1 ,κ 1 )]PF 6 (M, M′ = Rh, Ir), in stepwise ways (Scheme b) . The M 2 bridge of meso ‐dpmppm‐κ 3 ,κ 1 (Scheme c) was also found in [M 2 (µ‐ meso ‐dpmppm‐κ 3 ,κ 1 ) 2 ] 2+ and [M 2 (µ‐ meso ‐dpmppm‐κ 3 ,κ 1 )(XylNC) 3 ] 2+ (M = Pd, Pt),, and recently, the latter Pt 2 complex was expanded by reacting with Pt 0 (dba) 2 up to a decanuclear Pt complex, [{Pt 3 (µ‐dpmppm‐κ 2 ,κ 1 ,κ 1 )(XylNC) 5 } 2 Pt 4 (XylNC) 8 ] 6+ , in which meso ‐dpmppm ligands connected three Pt centers in κ 2 ,κ 1 ,κ 1 fashion .…”

Synthesis and structures of dinuclear RhIII and IrIII complexes supported by a tetraphosphine, meso- or rac-bis{[(diphenylphosphinomethyl)phenyl]phosphino]}methane

“…The flexible coordination behavior of mesodpmppm further organized stepwise assemblies of heterotrinuclear metal ions of [PdCl 2 (Cp*M 0 Cl 2 )(Cp*MCl 2 )(m-dpmppmk 2 ,k 1 ,k 1 )] and [PdCl(m-Cl)(Cp*M 0 Cl)(Cp*MCl 2 )(m-dpmppm-k 2 ,k 1 ,k 1 )] þ (M, M 0 ¼ Rh, Ir, Cp* ¼ h 5 -pentamethylcyclopentadienyl) [38]. In addition, we have recently been successful in establishing lowvalent octapalladium chains supported by meso-dpmppm, as a coordinatively unsaturated Pd 8 rod, [Pd 8 (m-dpmppm) 4 ](BF 4 ) 4 , and the terminal-capped [Pd 8 (m-dpmppm) 4 (L) 2 ](BF 4 ) 4 (L ¼ 2,6-xylyl isocyanide (XylNC), CH 3 CN, N,N-dimethylformamide (dmf)) [39,40].…”