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.

Syntheses, rearrangements, and structural analyses of unsaturated nitrogen donor ligands derived from diphenyldiazomethane and the chiral rhenium Lewis acid [(η5-C5H5)Re(NO)(PPh3)].

Diphenyldiazomethane and a labile chlorobenzene complex of [(η5-C5H5)Re(NO)(PPh3)]+ BF4- react to give the η1 adduct [(η5-C5H5)Re(NO)(PPh3)(NNCPh2)]+ BF4- (73%). When this is conducted in the presence of copper powder, a 3-phenyl-1H-indazole complex derived from carbon-hydrogen bond activation, [(η5-C5H5)Re(NO)(PPh3)(NC(Ph)CCHCHCHCHCNH)]+ BF4-, is obtained (65%). Subsequent reaction with NaOCH3 gives indazolyl complex (η5-C5H5)Re(NO)(PPh3)(NCCHCHCHCHCC(Ph)N) (85%), derived from NH deprotonation and a 1,2-rhenium shift. Crystal structures of the three new complexes are determined. DFT calculations are used to probe the mechanism of the 1,2-shift and energetics of alternative Re-N rotamers and linkage isomers, and assign bond orders and dominant resonance formulations.

Direct observation of ß-chloride elimination from an isolable ß-chloroalkyl complex of square-planar nickel.

Reported here are the isolation, structural characterization, and decomposition kinetics of the four-coordinate pentachloroethyl nickel complex, NiCl(CCl2CCl3)(CNAr(Mes2))2 (Ar(Mes2) = 2,6-(2,4,6-Me3C6H2)2C6H3). This complex is a unique example of a kinetically persistent ß-chloroalkyl in a system relevant to coordination-insertion polymerization of polar olefins. Kinetic analysis of NiCl(CCl2CCl3)(CNAr(Mes2))2 decomposition indicates that ß-chloride (ß-Cl) elimination proceeds by a unimolecular mechanism that does not require initial dissociation of a CNAr(Mes2) ligand. The results suggest that a direct ß-Cl elimination pathway is available to four-coordinate, Group 10 metal vinyl chloride polymerization systems.