Synthesis, reactivity, structures, and dynamic properties of gyroscope like iron complexes with dibridgehead diphosphine cages: pre- vs. post-metathesis substitutions as routes to adducts with neutral dipolar Fe(CO)(NO)(X) rotors

Abstract

Three routes are explored to the title halide/cyanide complexes trans-Fe(CO)(NO)(X)(P((CH))P) (9c-X; X = Cl/Br/I/CN), the Fe(CO)(NO)(X) moieties of which can rotate within the diphosphine cages (ΔH/ΔS (kcal mol/eu) 5.9/-20.4 and 7.4/-23.9 for 9c-Cl and 9c-I from variable temperature C NMR spectra). First, reactions of the known cationic complex trans-[Fe(CO)(NO)(P((CH))P)] BF and BuN X give 9c-Cl/-Br/-I/-CN (75-83%). Second, reactions of the acyclic complexes trans-Fe(CO)(NO)(X)(P((CH)CH[double bond, length as m-dash]CH)) and Grubbs' catalyst afford the tris(cycloalkenes) trans-Fe(CO)(NO)(X)(P((CH)CH[double bond, length as m-dash]CH(CH))P) (m/X = 6/Cl,Br,I,CN, 7/Cl,Br, 8/Cl,Br) as mixtures of Z/E isomers (24-41%). Third, similar reactions of trans-[Fe(CO)(NO)(P((CH)CH[double bond, length as m-dash]CH))] BF and Grubbs' catalyst afford crude trans-[Fe(CO)(NO)P((CH)CH[double bond, length as m-dash]CH(CH))P)] BF (m = 6, 8). However, the C[double bond, length as m-dash]C hydrogenations required to consummate routes 2 and 3 are problematic. Crystal structures of 9c-Cl/-Br/-CN are determined. Although the CO/NO/X ligands are disordered, the void space within the diphosphine cages is analyzed in terms of horizontal and vertical constraints upon Fe(CO)(NO)(X) rotation and the NMR data. The molecules pack in identical motifs with parallel P-Fe-P axes, and without intermolecular impediments to rotation in the solid state.

Syntheses, Structures, and Thermal Properties of Gyroscope-like Complexes Consisting of PtCl2 Rotators Encased in Macrocyclic Dibridgehead Diphosphines P((CH2)n)3P with Extended Methylene Chains (n = 20/22/30) and Isomers Thereof

“…In some cases, the yields of trans - 2 are modest. However, trigonal bipyramidal Fe­(CO) 3 adducts of the same dibridgehead diphosphines (as well as homologues with fewer methylene groups) can be similarly accessed in higher yields, as rationalized elsewhere. − Palladium analogues of trans - 2 have also been described. , With all MCl 2 adducts, rotation is fast on the NMR time scale, even at −100 °C.…”

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

“…Representative examples with square planar complexes are shown in Scheme 1 . Analogous sequences with trigonal bipyramidal substrates proceed in somewhat higher overall yields, as analyzed elsewhere [ 1 – 4 ]. Setaka has developed a similar chemistry in which the phosphorus atoms are replaced by silicon and the metal fragment by p -phenylene ( p -C 6 H 4 ) or related aromatic moieties [ 14 – 19 ].…”

“…The analogous Fe(CO) 3 adducts are easily prepared [ 1 – 4 ], but in efforts to date it has not been possible to efficiently remove the dibridgehead diphosphine ligands from the low cost iron fragment. Oxidations that lead to the corresponding dibridgehead diphosphine dioxides (O=)P((CH 2 ) n ) 3 P(=O) have exhibited promise, but purification has been problematic [ 24 ].…”

Partially Shielded Fe(CO)3 Rotors: Syntheses, Structures, and Dynamic Properties of Complexes with Doubly trans Spanning Diphosphines, trans-Fe(CO)3(PhP((CH2)n)2PPh)

“…The intersection of alkene metathesis and inorganic or organometallic synthesis has proved to be a rich area, allowing targeted approaches to a variety of complex metal-containing molecules. , We evolved initial interests in metallomacrocycle and metallamacrocycle syntheses ( I and II in Scheme ) , into a program involving gyroscope-like complexes of the general type IIIa . − These are distinguished by three methylene chains that span two trans -phosphorus donor atoms and are assembled by alkene metathesis/hydrogenation sequences. Some of the most interesting and intensively studied species have trigonal planar iron carbonyl cores or “rotators” (Fe­(CO) 3 , Fe­(CO) 2 (NO) + , Fe­(CO)­(NO)­(X)) within the di bridgehead di phosphine “stators”. Many crystal structures and barriers to Fe­(CO)­(L)­(L′) rotation have been determined.…”