title: Gyroscope-like molecules consisting of PdX₂/PtX₂ rotators within three-spoke dibridgehead diphosphine stators: syntheses, substitution reactions, structures, and dynamic properties.
abstract: Threefold intramolecular ring-closing metatheses of trans-[MCl2(P{(CH2)(m)CH=CH2}3)2] are effected with Grubbs' catalyst. Following hydrogenation catalyzed by [RhCl(PPh3)3], the title complexes trans-[MCl2(P((CH2)n)3P)] (n=2m+2; M/n=Pt/14, 4 c; Pt/16, 4 d; Pt/18, 4 e; Pd/14, 5 c; Pd/18, 5 e) and sometimes isomers partly derived from intraligand metathesis, trans-[MCl2{P(CH2)n(CH2)n}P(CH2)n)] (4'c-e, 5'e), are isolated. These react with LiBr, NaI, and KCN to give the corresponding MBr2, MI2, and M(CN)2 species (58-99%). (13)C NMR data show that the MX2 moieties rapidly rotate within the diphosphine cage on the NMR timescale, even at -120 °C. The reaction of 4 c and KSCN gives separable Pt(NCS)2 and Pt(NCS)(SCN) adducts (13 c, 28%; 14 c, 20%), and those of 4 c,e and Ph2Zn give PtPh2 species (15 c, 61%; 15 e, 90%). (13)C NMR spectra of 13 c-15 c show two sets of CH2 signals (ca. 2:1 intensity ratios), indicating that MX2 rotation is no longer rapid. Reactions of 4 c or 4'c and excess NaC≡CH afford the free diphosphines P{(CH2)14}3P (91%) and (CH2)14P(CH2)14P(CH2)14 (90%). The latter has been crystallographically characterized as a bis(BH3) adduct. The crystal structures of eight complexes with P(CH2)14P linkages (PtCl2, PtBr2, PtI2, Pt(NCS)2, PtPh2, PdCl2, PdBr2, PdI2) and 15 e have been determined, and intramolecular distances analyzed with respect to MX2 rotation. The conformations of the (CH2)14 moieties and features of the crystal lattices are also discussed.
authors.affiliation: Institute of Organic Chemistry and Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestrasse 42, 91054 Erlangen (Germany).
authors.forename: Agnieszka J
authors.initials: AJ
authors.lastname: Nawara-Hultzsch
authors.forename: Michael
authors.initials: M
authors.lastname: Stollenz
authors.forename: Michał
authors.initials: M
authors.lastname: Barbasiewicz
authors.forename: Sławomir
authors.initials: S
authors.lastname: Szafert
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Lis
authors.forename: Frank
authors.initials: F
authors.lastname: Hampel
authors.forename: Nattamai
authors.initials: N
authors.lastname: Bhuvanesh
authors.forename: John A
authors.initials: JA
authors.lastname: Gladysz
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006219:Halogens / Q000737:chemistry; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D010165:Palladium / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry; D010984:Platinum / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D006219:Halogens; D010720:Phosphines; D010984:Platinum; D010165:Palladium; C044646:phosphine
keywords: diphosphine ligands; hydrogenation; olefin metathesis; palladium; platinum; substitution reactions