Dinuclear Rh^II-Phthalocyaninates with a Rh-Rh Single Bond: X-ray Crystal Structure of Di(pyridinephthalocyaninato(2-)rhodium(II))

Abstract

<jats:p> Red, diamagnetic di(phthalocyaninato(2-)rhodium(II)), [( Rhpc <jats:sup>2−</jats:sup>)<jats:sub>2</jats:sub>] is prepared by thermal decomposition of acidophthalocyaninatorhodium(III) or di(acido)phthalocyaninatorhodates(III) in inert, high boiling solvents or under reduced pressure at T &lt; 350° C . It is insoluble in most common solvents except pyridine ( py ), yielding red, diamagnetic di(pyridinephthalocyaninato(2-)rhodium(II)), [{ Rh ( py ) pc <jats:sup>2−</jats:sup>}<jats:sub>2</jats:sub>]. This crystallizes as benzene solvate in the cubic space group Ia-3 (no. 206) (a = 35.960(7) Å) with Z = 24. The Rh - Rh distance (d( Rh - Rh ) = 2.741(2) Å) indicates a strong unsupported Rh - Rh single bond. Due to the axial coordination of py the Rh atoms are virtually bonded in the centre ( ct ) of the pc <jats:sup>2−</jats:sup> core (d( Rh - ct ) = 0.08(1) Å). The pc <jats:sup>2−</jats:sup> ligands are staggered with the skew angle φ( N <jats:sub> iso </jats:sub>- Rh - Rh '- N <jats:sub> iso </jats:sub>') = 42(1)°. Asymmetrical doming of the pc <jats:sub>2−</jats:sub> ligands is caused by a short interplanar distance (d( ct - ct ) = 2.89(1) Å) and axial coordination of pyridine. Due to the labilizing trans influence of the Rh - Rh bond the d( Rh - N <jats:sub> py </jats:sub>) = 2.309(8) Å is rather long. Two quasi-reversible anodic and four cathodic electron transfer processes are observed in the differential pulse voltammogram of [{ Rh ( py ) pc <jats:sup>2−</jats:sup>}<jats:sub>2</jats:sub>] at 0.81, 0.55, −0.33, −0.50, −0.75 and −1.33 V. The UV/vis NIR spectrum of [{ Rh ( py ) pc <jats:sup>2−</jats:sup>}<jats:sub>2</jats:sub>] shows the typical π-π* transitions of the pc <jats:sup>2−</jats:sup> ligand. The B region is split into two bands at 15 440 ( B <jats:sup>−</jats:sup>) and 16 890 cm<jats:sup>−1</jats:sup>( B <jats:sup>+</jats:sup>) of equal intensity due to strong excitonic coupling. The totally symmetric Rh - Rh stretching vibration is selectively enhanced in the Fourier Transform–Raman spectrum at 176 cm<jats:sup>−1</jats:sup>. </jats:p>

Assembled structures of tetrakis(biimidazole)dirhodium complexes hydrogen-bonded with common inorganic anions

“…[Rh 2 (EtCN) 10 ] 4+ has the shortest distance of 2.604 (1) Å among the reported structures. Repulsion between the equatorial ligands made the Rh-Rh distance longer, as observed in [Rh 2 (dmg) 4 (py) 2 ] (Hdmg = dimethylglyoxime; Kuz'menko et al, 1991) or [Rh 2 (pc) 2 (py) 2 ] (H 2 pc = phthalocyanine; Huckstadt et al, 1997). A strong donor axial ligand also changed the distance that is observed between [Rh 2 (dmg) 4 (PPh 3 ) 2 ] (Caulton & Cotton, 1971) and [Rh 2 (dmg) 4 (py) 2 ].…”

“…Rh-Rh (Å ) Reference (Caulton & Cotton, 1971;Dikareva et al, 1989;Dunbar, 1988;Huckstadt et al, 1997;Inoki et al, 2012;Kuz'menko et al, 1991;Li et al, 2013;Olmstead & Balch, 1978;Prater et al, 1999). [Rh 2 (EtCN) 10 ] 4+ has the shortest distance of 2.604 (1) Å among the reported structures.…”

Assembled structures of tetrakis(biimidazole)dirhodium complexes hydrogen-bonded with common inorganic anions

“…[Rh 2 (EtCN) 10 ] 4+ has the shortest distance of 2.604 (1) Å among the reported structures. Repulsion between the equatorial ligands made the Rh-Rh distance longer, as observed in [Rh 2 (dmg) 4 (py) 2 ] (Hdmg = dimethylglyoxime; Kuz'menko et al, 1991) or [Rh 2 (pc) 2 (py) 2 ] (H 2 pc = phthalocyanine; Huckstadt et al, 1997). A strong donor axial ligand also changed the distance that is observed between [Rh 2 (dmg) 4 (PPh 3 ) 2 ] (Caulton & Cotton, 1971) and [Rh 2 (dmg) 4 (py) 2 ].…”

“…Rh-Rh (Å ) Reference (Caulton & Cotton, 1971;Dikareva et al, 1989;Dunbar, 1988;Huckstadt et al, 1997;Inoki et al, 2012;Kuz'menko et al, 1991;Li et al, 2013;Olmstead & Balch, 1978;Prater et al, 1999). [Rh 2 (EtCN) 10 ] 4+ has the shortest distance of 2.604 (1) Å among the reported structures.…”

Synthesis and Reactivity of Porphyrinatorhodium(II)−Triethylphosphine Adducts: The Role of PEt3in Stabilizing a Formal Rh(II) State

“…The resulting adduct dissociates because it has zero Rh−Rh bond order: dπ 4 δ 2 (δ*) 2 (dπ*) 4 (pπ* por ) 2 (dσ) 0 . It is well known that axial ligation of non-porphyrin Rh II dimers induces such destabilization of the dσ Rh - Rh orbital that in many cases it becomes the HOMO of the resulting adduct. 40e, …”

Paramagnetic Rh(III) Complexes from Reactions of Phosphines with Hydride-Bridged and Nonbridged Rhodium Phthalocyanine Dimers: Metal-to-Ligand Charge Transfer Induced by Phosphines

“…Therefore, the two (RPc)Rh macrocycles of 7a are either exactly eclipsed or exactly 45°-staggered. However, the exactly eclipsed isomer can be ruled out if we assume that the Rh−Rh bond length of 7 is close to that of [(Pc)(py)Rh] 2 , i.e., 2.74 Å . Such a short distance between the two (RPc)Rh macrocycles results in repulsion between the π-electrons of the two (RPc)Rh macrocycles and precludes the formation of the exactly eclipsed isomer.…”

Assembled structures of tetrakis(biimidazole)dirhodium complexes hydrogen-bonded with common inorganic anions

“…[Rh 2 (EtCN) 10 ] 4+ has the shortest distance of 2.604 (1) Å among the reported structures. Repulsion between the equatorial ligands made the Rh-Rh distance longer, as observed in [Rh 2 (dmg) 4 (py) 2 ] (Hdmg = dimethylglyoxime; Kuz'menko et al, 1991) or [Rh 2 (pc) 2 (py) 2 ] (H 2 pc = phthalocyanine; Huckstadt et al, 1997). A strong donor axial ligand also changed the distance that is observed between [Rh 2 (dmg) 4 (PPh 3 ) 2 ] (Caulton & Cotton, 1971) and [Rh 2 (dmg) 4 (py) 2 ].…”

“…Rh-Rh (Å ) Reference (Caulton & Cotton, 1971;Dikareva et al, 1989;Dunbar, 1988;Huckstadt et al, 1997;Inoki et al, 2012;Kuz'menko et al, 1991;Li et al, 2013;Olmstead & Balch, 1978;Prater et al, 1999). [Rh 2 (EtCN) 10 ] 4+ has the shortest distance of 2.604 (1) Å among the reported structures.…”

Synthesis and Reactivity of Porphyrinatorhodium(II)−Triethylphosphine Adducts: The Role of PEt3in Stabilizing a Formal Rh(II) State

“…The resulting adduct dissociates because it has zero Rh−Rh bond order: dπ 4 δ 2 (δ*) 2 (dπ*) 4 (pπ* por ) 2 (dσ) 0 . It is well known that axial ligation of non-porphyrin Rh II dimers induces such destabilization of the dσ Rh - Rh orbital that in many cases it becomes the HOMO of the resulting adduct. 40e, …”

Paramagnetic Rh(III) Complexes from Reactions of Phosphines with Hydride-Bridged and Nonbridged Rhodium Phthalocyanine Dimers: Metal-to-Ligand Charge Transfer Induced by Phosphines

“…Therefore, the two (RPc)Rh macrocycles of 7a are either exactly eclipsed or exactly 45°-staggered. However, the exactly eclipsed isomer can be ruled out if we assume that the Rh−Rh bond length of 7 is close to that of [(Pc)(py)Rh] 2 , i.e., 2.74 Å . Such a short distance between the two (RPc)Rh macrocycles results in repulsion between the π-electrons of the two (RPc)Rh macrocycles and precludes the formation of the exactly eclipsed isomer.…”

Assembled structures of tetrakis(biimidazole)dirhodium complexes hydrogen-bonded with common inorganic anions

“…[Rh 2 (EtCN) 10 ] 4+ has the shortest distance of 2.604 (1) Å among the reported structures. Repulsion between the equatorial ligands made the Rh-Rh distance longer, as observed in [Rh 2 (dmg) 4 (py) 2 ] (Hdmg = dimethylglyoxime; Kuz'menko et al, 1991) or [Rh 2 (pc) 2 (py) 2 ] (H 2 pc = phthalocyanine; Huckstadt et al, 1997). A strong donor axial ligand also changed the distance that is observed between [Rh 2 (dmg) 4 (PPh 3 ) 2 ] (Caulton & Cotton, 1971) and [Rh 2 (dmg) 4 (py) 2 ].…”

“…Rh-Rh (Å ) Reference (Caulton & Cotton, 1971;Dikareva et al, 1989;Dunbar, 1988;Huckstadt et al, 1997;Inoki et al, 2012;Kuz'menko et al, 1991;Li et al, 2013;Olmstead & Balch, 1978;Prater et al, 1999). [Rh 2 (EtCN) 10 ] 4+ has the shortest distance of 2.604 (1) Å among the reported structures.…”

Synthesis and Reactivity of Porphyrinatorhodium(II)−Triethylphosphine Adducts: The Role of PEt3in Stabilizing a Formal Rh(II) State

“…The resulting adduct dissociates because it has zero Rh−Rh bond order: dπ 4 δ 2 (δ*) 2 (dπ*) 4 (pπ* por ) 2 (dσ) 0 . It is well known that axial ligation of non-porphyrin Rh II dimers induces such destabilization of the dσ Rh - Rh orbital that in many cases it becomes the HOMO of the resulting adduct. 40e, …”

Paramagnetic Rh(III) Complexes from Reactions of Phosphines with Hydride-Bridged and Nonbridged Rhodium Phthalocyanine Dimers: Metal-to-Ligand Charge Transfer Induced by Phosphines

“…Therefore, the two (RPc)Rh macrocycles of 7a are either exactly eclipsed or exactly 45°-staggered. However, the exactly eclipsed isomer can be ruled out if we assume that the Rh−Rh bond length of 7 is close to that of [(Pc)(py)Rh] 2 , i.e., 2.74 Å . Such a short distance between the two (RPc)Rh macrocycles results in repulsion between the π-electrons of the two (RPc)Rh macrocycles and precludes the formation of the exactly eclipsed isomer.…”