Syntheses, Structures, Reactivities, and Dynamic Properties of Gyroscope-like Complexes Consisting of Rh(CO)(X) or Rh(CO)₂(I) Rotators and Cage-likeTransAliphatic Dibridgehead Diphosphine Stators

Abstract

Square planar trans-Rh­(CO)­(Cl)­[P­((CH2)14)3 P] (4c) is prepared from trans-Rh­(CO)­(Cl)­[P­((CH2)6CHCH2)3]2 by a CC metathesis/hydrogenation sequence (41%). Additions of NaBr, NaI, or KSCN give the substitution products trans-Rh­(CO)­(X)­[P­((CH2)14)3 P] (X = Br/I/–NCS, 5c/6c/7c, 97–44%). Additions of ZnPh2, MeLi, or NaBH4 give trans-Rh­(CO)­(R)­[P­((CH2)14)3 P] (R = Ph/Me, 8c/9c, ∼94–89%) or trans-Rh­(CO)­(H2BH2)­[P­((CH2)14)3 P] (10c, 99%). Reactions with BrCCl3 or CO give the octahedral or trigonal bipyramidal addition products trans-Rh­(CO)­(Cl)­(Br)­(CCl3)­[P­((CH2)14)3P] (11c, 97%) or trans-Rh­(CO)2(I)­[P­((CH2)14)3 P] (12c, ∼98%). The crystal structures of 5c, 6c, 8c, and 10c are determined. These and other data are used to calculate the dimensions of the rotators and void spaces of the diphosphine cages, aiding the interpretation of dynamic properties. Specifically, 4c–6c and 9c–10c exhibit a single set of seven CH2 13C NMR signals at room temperature, although three sets of seven are expected from symmetry (⇒ facile 360° Rh­(CO)­(X) rotation); 7c–8c exhibit two sets of seven signals with a ca. 2:1 area ratio (∼90° Rh­(CO)­(X) rotation); 11c exhibits three sets of seven signals (no Rh­(CO)­(Cl)­(Br)­(CCl3) rotation). The barrier to Rh­(CO)2(I) rotation in 12c is bounded as higher than that of Rh­(CO)­(I) rotation in 6c, but the rotamers preferentially interconvert via CO dissociation/addition. Reaction of 4c and excess PMe3 gives trans-Rh­(CO)­(Cl)­(PMe3)2 (72%) and the dibridgehead diphosphine P­((CH2)14)3P (58%). The latter reacts with [(OC)2Rh­(μ-Cl)]2 to regenerate 4c (58%).

Square-Planar and Octahedral Gyroscope-Like Metal Complexes Consisting of Dipolar Rotators Encased in Dibridgehead Di(triaryl)phosphine Stators: Syntheses, Structures, Dynamic Properties, and Reactivity

“…All reactions were conducted under N 2 or H 2 atmospheres and worked up aerobically. Solvents and reagents were treated as described in the SI, and instrumentation was detailed in a previous paper in the series . NMR spectra are referenced as follows (δ/ppm): 1 H, residual internal CHCl 3 (7.23), C 6 D 5 H (7.15), CHDCl 2 (5.32), C 6 D 4 HCl (7.14), CHFCl 2 (7.47), C 6 D 5 CD 2 H (2.09); 13 C, internal CDCl 3 (77.16), C 6 D 6 (128.06), CD 2 Cl 2 (53.84), C 6 D 5 Cl (134.19), CDFCl 2 (104.2), C 6 D 5 CD 3 (20.4); 31 P, internal (capillary) or external H 3 PO 4 (0.00).…”

“…We have had a long-standing interest in the transition-metal-based rotors II (Scheme ), which feature two trans phosphorus donor atoms connected by three (CH 2 ) n bridges. − Together these comprise the cagelike stator. Such dibridgehead di­(trialkyl)­phosphine complexes are usually accessed via 3-fold ring-closing metatheses of square-planar, trigonal-bipyramidal, or octahedral precursors I .…”

“…Another driving force for this study was the potential for liberating free dibridgehead di­(triaryl)­phosphines IV (Scheme ) from the metal complexes. There are increasing numbers of avenues for preparing the aliphatic analogues P­((CH 2 ) n ) 3 P from II , , including from the rhodium adduct 1 -Cl . As detailed in the Discussion section, there is prior literature on dibridgehead di­(triaryl)­phosphines and related compounds, all with additional p -phenylene moieties in each bridge. , Importantly, as partially illustrated for IV , such compounds can potentially exist as in , in , out , out , and in , out isomers, a separate theme of great interest…”

A surprise landing on the terra incognita of macrocyclic dibridgehead diorganoarsines: syntheses, structures, and reactivities

“…The dibridgehead diphosphine literature is not as extensive, with species of the formula P((CH 2 ) n ) 3 P limited to n = 3-4 10 until our recent work extending n to 14 and 18. 11,12 In contrast, analogous dibridgehead diarsines As((CH 2 ) n ) 3 As (1) have remained unknown for all values of n, although systems with one or more short As(CRQCR)As or AsOAs bridges have been reported. 13 Our routes to the dibridgehead diphosphines P((CH 2 ) 14 ) 3 P and P((CH 2 ) 18 ) 3 P are stoichiometric in platinum 11 or rhodium,…”

“…Our routes to the dibridgehead diphosphines P((CH 2 ) 14 ) 3 P and P((CH 2 ) 18 ) 3 P are stoichiometric in platinum 11 or rhodium, 12 and other ring sizes are challenging to access due to low yield steps. In this communication, we report the serendipitous finding that the dibridgehead diarsines 1 are available by routes that involve an earth abundant metal, iron, and avoid low yield steps.…”