Templated Formation of Binuclear Macrocycles via Hemilabile Ligands

Abstract

A new approach to synthesizing binuclear metallomacrocycles is reported. This approach utilizes flexible bisphosphine alkyl−aryl ether hemilabile ligands which complex Rh(I) to form “condensed” macrocycles held together by a series of both strong and weak links of the following type: [(κ2:μ2:κ2-(1,4-(Ph2PCH2CH2O)2-2,3,5,6-((CH3)4C6)))2Rh2][BF4]2 (5a) or [(μ2,η1:η6:η1-(1,4-(Ph2P(CH2) n O)2-X))2Rh2][BF4]2 (5b, n = 2, X = 2,3,5,6-((CH3)4C6); 6, n = 3, X = 2,3,5,6-((CH3)4C6); 7, n = 2, X = C6H4; 8, n = 2, X = C6H4−C6H4). Introduction of ligands that will bind to Rh(I) more strongly than either the Rh−η6-aryl or Rh−η1-ether weak links of 5a−8 results in the breaking of the weak links to form a series of 26−34-membered macrocyclic ring structures such as [(μ2-(1,4-(Ph2P(CH2) n O)2X))2(L1) m (L2) o Rh2][BF4]2 (9, n = 2, X = 2,3,5,6-((CH3)4C6)), L1 = CO, m = 6, L2 = none; 10, n = 2, X = C6H4, L1 = CO, m = 6, L2 = none; 11, n = 2, X= C6H4−C6H4; L1 = CO, m = 6, L2 = none; 12, n = 2, X = 2,3,5,6-((CH3)4C6)), L1 = CO, m = 2, L2 = CH3CN, o = 2; 13, n = 3, X = 2,3,5,6-((CH3)4C6)), L1 = CO, m = 2, L2 = CH3CN, o = 2; 14, n = 2, X = C6H4, L1 = CO, m = 2, L2 = CH3CN, o = 2; 15, n = 2, X = C6H4−C6H4, L1 = CO, m = 2, L2 = CH3CN, o = 2). These homobimetallic macrocycles can be used to sequester bifunctional aromatic molecules to form host−guest structures such as [(μ2-(1,4-(Ph2PCH2CH2O)2-2,3,5,6-((CH3)4C6)))2(CO)2(μ2-1,4-(−NC)2C6H4)Rh2][BF4]2 (16) and [(μ2-(1,4-(Ph2PCH2CH2O)2-2,3,5,6-((CH3)4C6)))2(CH3CN)2(μ2-1,4-(−CN)2C6H4)Rh2][BF4]2 (17). The synthetic methods described within this article represent a powerful new way of making binuclear macrocycles from flexible ligands in nearly quantitative yields. Moreover, the macrocycles are highly tailorable with respect to cavity size and hydrophobicity and the metals' steric and electronic environments. Solid-state structures as determined by single-crystal X-ray diffraction studies are presented for compounds 5a, 6, 7, 9, 10, 12, and 17.

Metal–Organic Frameworks and Self-Assembled Supramolecular Coordination Complexes: Comparing and Contrasting the Design, Synthesis, and Functionality of Metal–Organic Materials

“…At elevated temperatures, the condensed structure can be driven to the thermodynamic monomer species, however in practice this requires temperatures of over 100°C and the stability of the kinetic product is thus high enough to circumvent the unwanted thermodynamic sink. 82 …”

Bridged Dinuclear Tripodal Tris(amido)phosphane Complexes of Titanium and Zirconium as Diligating Building Blocks for Organometallic Polymers

“…The target bis-(phosphane) building blocks for such an approach are shown in Scheme 1, and feature a pair of metal-bearing tripodal tris(amido)phosphane ligands, as well as a bridge between the metal centers labeled M. The addition of suitable late-transition-metal fragments capable of bonding to two phosphane moieties, labeled MЈL n in Scheme 1, should provide a facile route to transition-metal-containing oligomers and polymers. Although there are a plethora of examples of bis(phosphanes) used as bridging ligands, [22][23][24] as well as flexible ligands incorporating hard and soft donors that have been utilized as building blocks for bimetallic and polynuclear early-late transition-metal clusters, [25,26] the complexes we propose here could provide rare examples of linear bis(phosphane) building blocks, [27][28][29][30][31][32] where throughspace interactions provide the potential for extended interactions. In this paper, we test the synthetic feasibility of preparing such building blocks using the diamagnetic early transition metals zirconium and titanium, with the goal of introducing redox active and paramagnetic metal-bridge fragments in future endeavours.…”

Rhodium: Organometallic Chemistry

“…These indicate the existence of distortions from idealized geometry involving a ''twist'' (127), where the axis of the double bond is no longer perpendicular to the molecular plane and a ''roll'' (128), where the line joining the midpoint of the double bond to the metal is no longer in the molecular plane. The latter distortion is seen for unsymmetrically substituted alkenes and occurs so as to place the more nucleophilic carbon atom closer to the molecular plane.…”

“…n = 2; R = H), while reaction of (175) with 1,4-diisocyanobenzene in acetonitrile forms the ''occupied'' metallamacrocycle (180). 128 The calixshaped metallacyclophane (181) is formed from 9,10-bis(2-diphenylphosphinoethyl)anthracene and [Rh(µ-Cl)(CO) 2 ] 2 at a low temperature. replaced by hexamethylbenzene to give [(η 5 -C 4 H 4 BPh)Rh(η 6 -C 6 Me 6 )]BF 4 , but if the acetonitrile complex is taken to dryness it polymerizes to (185).…”