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.

For a variety of purposes, it is of interest to embed metals in cagelike trans-spanning di(triaryl)phosphine ligands. Toward this end, a combination of P(p-C6H4O(CH2)mCH═CH2)3 [3; m = 4 (a), 5 (b), 6 (c), and 7 (d)], [Rh(COD)(µ-Cl)]2, and CO gives square-planar trans-Rh(CO)(Cl)[P(p-C6H4O(CH2)mCH═CH2)3]2 (4a-4d). Reactions of 4b-4d with Grubbs' catalyst (first generation) and then H2 (catalyst PtO2) yield the title compounds trans-Rh(CO)(Cl)[P(p-C6H4O(CH2)nO-p-C6H4)3P] (n = 2m + 2, 6b-6d; 26-41% from 4b-4d). Two are crystallographically characterized. The Cl-Rh-CO moieties rapidly rotate on the NMR time scale at -120 °C, per the ample clearance provided by the (CH2)n segments. Steric interactions with the PC6H4O linkages are analyzed. LiC≡CAr displaces the chloride ligand from 6b to give RhC≡CAr adducts (Ar = C6H5/p-C6H4CH3, 7b/8b). The ArC≡C-Rh-CO rotator of 7b rapidly rotates on the NMR time scale (-70 °C), but with 8b, the longer p-CH3C6H4C≡C group is confined between two (CH2)12 bridges, even at 120 °C. Reactions of Re(CO)5(X) and 3c (140 °C) give octahedral mer,trans-Re(CO)3(X)[P(p-C6H4O(CH2)6CH═CH2)3]2 (X = Cl/Br), and metathesis/hydrogenation sequences yield mer,trans-Re(CO)3(X)[P(p-C6H4O(CH2)14O-p-C6H4)3P]. Reactions of 6c and 6d and excess PMe3 give the free diphosphines P(p-C6H4O(CH2)nO-p-C6H4)3P (14c and 14d, 83-75%). The addition of 14d to [Rh(CO)2(µ-Cl)]2 reconstitutes 6d (87%). Both in,in and out,out isomers of 14c and 14d are possible, but low-temperature NMR spectra show one set of signals, consistent with rapid homeomorphic isomerizations that turn the molecules inside out. Thermolyses (C6D5Br, 140 °C) effect phosphorus inversion to give in,out isomers.

Three-Fold Intramolecular Ring Closing Alkene Metatheses of Square Planar Complexes with cis Phosphorus Donor Ligands P(X(CH2) mCH═CH2)3 (X = -, m = 5-10; X = O, m = 3-5): Syntheses, Structures, and Thermal Properties of Macrocyclic Dibridgehead Diphosphorus Complexes.

Reactions of cis-PtCl2(P((CH2) mCH═CH2)3)2 and Grubbs' first generation catalyst and then hydrogenations afford cis- PtCl2(P((CH2) n)3 P) ( cis-2; n = 2 m + 2 = 12 (b), 14 (c), 16 (d), 18 (e), 20 (f), 22 (g); 6-40%), derived from 3-fold interligand metatheses. The phosphite complexes cis-PtCl2(P(O(CH2) m*CH═CH2)3)2 are similarly converted to cis- PtCl2(P(O(CH2) n*O)3 P) ( cis-5; n* = 8 (a), 10 (b), 12 (c), 10-20%). The substitution products cis- PtPh2(P((CH2) n)3 P) ( cis-6c,d) and cis- PtI2(P(O(CH2)10O)3 P) are prepared using Ph2Zn and NaI, respectively. Crystal structures of cis-2c,d,f, cis-5a,b, and cis-6c show one methylene bridge that roughly lies in the platinum coordination plane and two that are perpendicular. The thermal behavior of the complexes is examined. When the bridges are sufficiently long, they rapidly exchange via an unusual "triple jump rope" motion over the PtX2 moieties. NMR data establish Δ H⧧, Δ S⧧, and Δ G298K⧧/Δ G393K⧧ values of 7.8 kcal/mol, -27.9 eu, and 16.1/18.8 kcal/mol for cis-2d, and a Δ G393K⧧ of ≥19.6 kcal/mol for the shorter bridged cis-2c. While cis-2c,g gradually convert to trans-2c,g at 150-185 °C in haloarenes, trans-2c,g give little reaction under analogous conditions, establishing the stability order trans > cis. Similar metathesis/hydrogenation sequences with octahedral complexes containing two cis phosphine ligands, fac-ReX(CO)3(P((CH2)6CH═CH2)3)2 (X = Cl, Br), give fac- ReX(CO)3( P(CH2)13 CH2)((CH2)14)( P(CH2)13 CH2) (19-50%), which are derived from a combination of interligand and intraligand metathesis. The relative stabilities of cis/ trans and other types of isomers are probed by combinations of molecular dynamics and DFT calculations.

Octahedral Gyroscope-like Molecules Consisting of Rhenium Rotators within Cage-like Dibridgehead Diphosphine Stators: Syntheses, Substitution Reactions, Structures, and Dynamic Properties.

Reactions of Re(CO)5(X) (X = Cl, Br) or [Re2(CO)4(NO)2(µ-Cl)2(Cl)2] and the phosphines P((CH2)mCH═CH2)3 (m = 6, a; 7, b; 8, c) give mer,trans-Re(CO)3(X)(P((CH2)mCH═CH2)3)2 (53-95%) or cis,trans-Re(CO) (NO) (Cl)2(P((CH2)6CH═CH2)3)2 (57%), respectively. Additions of Grubbs' catalyst (5-10 mol %, 0.0010-0.0012 M) and subsequent hydrogenations (PtO2, ≤5 bar) yield the gyroscope-like complexes mer,trans-R e(CO)3(X)(P((CH2)n)3 P) (n = 2m + 2; X = Cl, 7a,c; Br, 8a,c; 18-61%) or cis,trans-R e(CO)(NO)(Cl)2(P((CH2)14)3 P) (14%), respectively, and/or the isomers mer,trans-R e(CO)3(X)( P(CH2)n-1 CH2)((CH2)n)( P(CH2)n-1 CH2) (X = Cl, 7'a-c; Br, 8'b; 6-27%). The latter are derived from a combination of interligand and intraligand metatheses. Reactions of 7a or 8a with NaI, Ph2Zn, or MeLi give mer,trans-R e(CO)3(X)(P((CH2)14)3 P) (X = I, 11a; Ph, 12a; Me, 13a; 34-87%). The 13C NMR spectra of 7a-c, 8a-c, 11a, and 13a show rotation of the Re(CO)3(X) moieties to be fast on the NMR time scale at room temperature (and at -90 °C for 8a). In contrast, the phenyl group in 12a acts as a brake, and two sets of 13C NMR signals (2:1) are observed for the methylene chains. The crystal structures of 7a, 8a, 12a, and 13a are analyzed with respect to Re(CO)3(X) rotation in solution and the solid state.