Gyroscope-Like Complexes Based on Dibridgehead Diphosphine Cages That Are Accessed by Three-Fold Intramolecular Ring Closing Metatheses and Encase Fe(CO)₃, Fe(CO)₂(NO)⁺, and Fe(CO)₃(H)⁺Rotators

Abstract

Reactions of trans-Fe(CO)3(P((CH2)mCH═CH2)3)2 (m = a/4; b/5, c/6, e/8) and Grubbs' catalyst (12-24 mol %, CH2Cl2, reflux) give the cage-like trienes trans- Fe(CO)3(P((CH2)mCH═CH(CH2)m)3 P) (3a-c,e, 60-81%). Hydrogenations (ClRh(PPh3)3, 60-80 °C) yield the title compounds trans- Fe(CO)3(P((CH2)n)3 P) (4a-c,e, 74-86%; n = 2m + 2), which have idealized D3h symmetry. A crystal structure of 4c suggests enough van der Waals clearance for the Fe(CO)3 moiety to rotate within the three P(CH2)14P linkages; structures of E,E,E-3a show rotation to be blocked by the shorter P(CH2)4CH═CH(CH2)4P linkages. Additions of NO(+)BF4(-) give the isoelectronic and isosteric cations [ Fe(CO)2(NO)(P((CH2)n)3 P)](+)BF4(-) (5a-c(+)BF4(-); 81-98%). Additions of [H(OEt2)2](+)BArf(-) (BArf = B(3,5-C6H3(CF3)2)4) afford the metal hydride complexes mer,trans-[ Fe(CO)3(H)(P((CH2)n)3 P)](+)BArf(-) (6a-c,e(+)BArf(-); 98-99%). The behavior of the rotators in the preceding complexes is probed by VT NMR. At ambient temperature in solution, 5a,b(+)BF4(-) and 6a(+)BArf(-) show two sets of P(CH2)n/2 (13)C NMR signals (2:1), whereas 5c(+)BF4(-) and 6b,c(+)BArf(-) show only one. At higher temperatures, the signals of 5b(+)BF4(-) coalesce; at lower temperatures, those of 5c(+)BF4(-) and 6b(+)BArf(-) decoalesce. These data give ΔH(⧧)/ΔS(⧧) values (kcal/mol and eu) of 8.3/-28.4 and 9.5/-6.5 for Fe(CO)2(NO)(+) rotation (5b,c(+)) and 6.1/-23.5 for Fe(CO)3(H)(+) rotation (6b(+)). (13)C CP/MAS NMR spectra show that the Fe(CO)3 moiety in polycrystalline 4c (but not 4a) undergoes rapid rotation between -60 and 95 °C. Approaches to minimizing these barriers and developing molecular gyroscopes are discussed.

A Nontemplated Route to Macrocyclic Dibridgehead Diphosphorus Compounds: Crystallographic Characterization of a “Crossed‐Chain” Variant of in/out Stereoisomers

“…The spatial arrangements of the four vinyl groups in 3 ab′ and 3 bc′ are not conducive to intramolecular alkene metathesis (Figure ), which is consistent with the modest yields of the title molecules. In contrast, there is evidence for favorable or “preorganized” conformations with hexaolefinic bis(phosphine) Fe(CO) 3 complexes, analogous to the platinum and rhodium educts in Scheme . These give much higher overall yields of gyroscope‐like products (50–70 %).…”

Anisotropic Thermal Expansion as the Source of Macroscopic and Molecular Scale Motion in Phosphorescent Amphidynamic Crystals

“…To explore the dynamics of the tetra-fluorophenylene rotator of gold(I) complex 3,wecarried out variable temperature solid-state CPMAS 13 CNMR spectroscopy of 3 in the range of 189 Kto302 K. We observed no significant changes in the weak C-F signals assigned to the rotator, which occur as multiplets as ar esult of one,t wo and three bond C-F scalar coupling ( Figure S9). It is not possible to conclude whether the lack of an observable coalescence process is the result of very slow or static rotation, or the result of insufficient chemical shift differences between the sites related by the postulated two-fold flipping motion.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] We and others have addressed it by exploring the emergent properties of amphidynamic crystals,which are built with acombination of lattice forming elements and moving parts. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] To date, examples have been reported of amphidynamic crystals with the potential of controlling gas adsorption and desorption, [12,15] electric, [25][26][27][28]33] optic, [29,30] shape memory, [31][32][33] and luminescence, [35][36][37][38] among other properties. [9][10][11][12]34] One of the...…”

Anisotropic Thermal Expansion as the Source of Macroscopic and Molecular Scale Motion in Phosphorescent Amphidynamic Crystals

“…The design of molecular machines with applications in the macroscopic world remains a major challenge . We and others have addressed it by exploring the emergent properties of amphidynamic crystals, which are built with a combination of lattice forming elements and moving parts . To date, examples have been reported of amphidynamic crystals with the potential of controlling gas adsorption and desorption, electric, optic, shape memory, and luminescence, among other properties …”