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.

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

“…Two signals of each set exhibited phosphorus coupling. The overall pattern was quite similar to those shown by metal complexes with cis or trans coordinating diphosphine ligands of the formula ( 6 ) [ 6 – 7 12 – 13 35 ]. This suggested the diphosphine diborane structure 6 ·2BH 3 (see Scheme 2 ), which is derived from one metathesis involving alkenyl moieties on different phosphorus atoms, and two metatheses of alkenyl moieties on identical phosphorus atoms.…”

“…The yield was 10%. The structure has been confirmed by an independent synthesis (detachment of the diphosphine from a platinum complex followed by borane addition) and a crystal structure [ 6 ].…”

“…We subsequently developed an interest in the free dibridgehead diphosphine ligands P((CH 2 ) n ) 3 P ( n = 14, 2 ; 18, 3 ), prompted in part by the unexpected discovery of the facile demetalations shown in Scheme 1 [ 5 – 6 10 , 22 ]. Such compounds were previously known only for much smaller ring sizes ( n < 4) [ 23 ].…”

A Nontemplated Route to Macrocyclic Dibridgehead Diphosphorus Compounds: Crystallographic Characterization of a “Crossed‐Chain” Variant of in/out Stereoisomers

“…This diphosphine dioxide, which features two remotely situated 13‐membered rings, is derived from the metathesis of (CH 2 ) 5 CH=CH 2 moieties on the same, as opposed to different, phosphorus atoms. In previous papers, we have designated such isomers by a prime following the Arabic numeral (i.e., 4′bc′ ). This structure also exhibits a C 2 symmetry axis that exchanges the (O=)P moieties.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…288) prepared via a kinetic resolution using a racemic diene and a enantioselective molybdenum metathesis catalyst [737]; and (13) interligand-bridged metal complexes (e.g. 290) [738]. Formation of a bicyclic phosphate (e.g.…”