SYNTHESIS AND X-RAY AND NEUTRON STRUCTURES OF ANTI-[L2RH2(H)2(MU-H)2](PF6)2 (L = 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE) AND A RELATED SPECIES CONTAINING A SYN-[RH2(H)2(MU-H)2]2- ISOLATION OF [L2FE2(MU-H)3]BPH4( CORE )
D. Hanke et al., SYNTHESIS AND X-RAY AND NEUTRON STRUCTURES OF ANTI-[L2RH2(H)2(MU-H)2](PF6)2 (L = 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE) AND A RELATED SPECIES CONTAINING A SYN-[RH2(H)2(MU-H)2]2- ISOLATION OF [L2FE2(MU-H)3]BPH4( CORE ), Inorganic chemistry, 32(20), 1993, pp. 4300-4305
The macrocyclic ligands 1,4,7-trimethyl-1,4,7-triazacyclononane (L) an
d -bis(4,7-dimethyl-1,4,7-triaza-1-cyclononyl)ethane (Me4dtne) react w
ith RhCl3.3H2O in ethanol affording the neutral complexes LRhCl3 (1) a
nd [(Me4dtne)Rh2Cl6]2H2O (2). Aqueous suspensions of 1 and 2 react wit
h NaBH4 yielding upon addition of KPF6 red-brown crystals of air- and
moisture-stable anti-[L2Rh2(H)2(mu-H)2](PF6)2 (3) and syn-[(Me4dtne)Rh
2(H)2(mu-H)2](PF6)2 (4), respectively, LFeCl3 and Li[AH4] were found t
o form red [L2Fe2(mu-H)3]BPh4 (5) in tetrahydrofuran. The structure of
3 has been determined by single-crystal X-ray (295 K) and neutron dif
fraction (20 K). Neutron data for 3: monoclinic space group P2(1)/c, a
= 8.155(l) angstrom, b = 11.768(2) angstrom, c = 15.611(2) angstrom,
beta = 92.156(8)-degrees, V = 1497.1(2) angstrom3, Z = 2, D(calcd) = 1
.869 g/cm3. The [HRh(mu-H)2RhH]2+ core contains a planar Rh2(mu-H)2 ri
ng (Rh-H(b) = 1.754(2) angstrom; Rh ... Rh = 2.595(2) angstrom); each
rhodium center has a terminal hydride ligand in anti-position with res
pect to each other (Rh-H(t) = 1.536(2) angstrom). The terminal hydride
exerts a pronounced structural trans influence on the Rh-N bond in tr
ans position (Rh-N(trans) = 2.276(1) angstrom vs average Rh-N(cis) = 2
.082(1) angstrom. In 4 the [HRh(mu-H)2RhH]2+ core is syn configurated
due to the steric requirements of the strapped macrocycle. The solutio
n behavior of 3 and 4 has been studied by H-1 NMR spectroscopy. 3 is a
fluctional molecule, and in contrast, 4 is rigid at ambient temperatu
re.