Labile Complexes of the [RuTp(pn)]⁺ (Tp = Tripyrazolylborate, pn = Ph₂PCH₂CH₂NMe₂) Fragment Including the Dinitrogen Ligand¹

Abstract

The [TpRu(pn)](+) fragment (Tp = tripyrazolyl, pn = Ph(2)PCH(2)CH(2)NMe(2)), featuring a strong sigma acceptor and a weak pi donor, forms reversible complexes with a variety of sigma donor ligands L including N(2) which appears to be more strongly bonded than even CH(3)CN. X-ray crystal structures of the complexes with L = H(2)O, acetone, CO, N(2), and vinylidene are included (adding to that for L = CH(3)CN from former work), as well as a comparative MO study on the bonding nature of L. The sequence of complex stabilities of [TpRu(pn)L](+) is CF(3)SO(3)(-) < acetone approximately H(2)O < CH(3)CN < N(2) < CO < vinylidene as suggested from EHMO calculations and crystallographic data as well as qualitative experimental results. Despite the notable stability of [TpRu(pn)(eta(1)-N(2))](+), the N-N bond length is 1.097(5) Å, exactly that in free N(2). Our analysis suggests that the insensitivity of the N-N bond essentially originates from the counterbalance of pi bond weakening (through back-donation) and sigma bond strengthening (through reducing the antibonding character of the sigma (2sigma(u)) MO in molecular dinitrogen.

Ruthenium(II) tris(pyrazolyl)borate complexes.† Reversible vinylidene complex formation

“…In the IR spectrum the ν(C᎐ ᎐ O) band is observed at 1640 cm Ϫ1 , in line with other ruthenium dmf complexes. 5,12 This value is below that of free dmf observed at 1675 cm Ϫ1 , implying, as expected, that co-ordination decreases the C᎐ ᎐ O bond strength. The ν(B᎐H) vibration is found at 2480 cm Ϫ1 which is characteristic of HB(pz) 3 when terdentate N,NЈ,NЉ-bonded to a metal center.…”

“…C 32 H 31 BClN 6 O 2 PRu requires C, 54.14; H, 4.40; N, 11.84%). NMR (CDCl 3 , 20 ЊC): δ H 7.90 (d, 1 H, J = 2.0, borate), 7.71 (d, 1 H, J = 2.0, borate), 7.69 (d, 1 H, J = 2.4, borate), 7 H,Ph,borate),9 H,Ph),6.68 (d,1 H, J = 2.0, borate), 6.33 (d, 1 H, J = 2.0, borate), 6.19 (m, 1 H, borate), 5.93 (dd, 1 H, J = 2.0, 2.0, borate), 5.77 (dd, 1 H, J = 2.3, 2.3, borate), 4.70 (d, 1 H, 4 5 of Ph), 106.45 (d, 4 J CP = 2.5, borate), 106.35 (borate), 106.26 (d, 3…”

“…This is in sharp contrast to the robustness of the cationic complex [Ru{HB(pz) 3 }(Ph 2 PCH 2 CH 2 NMe 2 )(᎐ ᎐ C᎐ ᎐ CHPh)] ϩ described previously. 5 The question is whether this is an ordinary effect of charge due to different Coulomb forces or due to some other effects, treatable by the concepts of MO theory. For this purpose we include extended Hückel (EH) calculations, although these cannot account for charge effects.…”

Transition metal complexes bearing a 2,2-bis(3,5-dimethylpyrazol-1-yl)propionate ligand: one methyl more matters

“…Similar dinitrogen complexes with cyclopentadienyl (Cp) and hydrotris(pyrazolyl)borate (Tp) ligands have been reported earlier by Kirchner, Mereiter, Valerga, Puerta and Moro-oka. [21][22][23][24][25][26] In order to synthesize the dinitrogen complex 7 methodically, 6 was dissolved in THF under a dinitrogen atmosphere and stirred at room temperature. After a few minutes, a yellow solid started to precipitate from the initially red solution.…”

Reactions of ruthenium(II) tris(pyrazolyl)borate and tris(pyrazolyl)methane complexes with diphenylvinylphosphine and 3,4-dimethyl-1-phenylphosphole

“…The inability to remove CH 3 CN thermally or to be displaced by terminal alkynes in these complexes is consistent with the stabilities of other ruthenium tris(pyrazolyl)borate acetonitrile complexes. For example, the stability of the complexes [(Tp)Ru(tmeda)L] ' (tmeda 0/Me 2 NCH 2 CH 2 NMe 2 ) was found to increase with L in the order L 0/THF B/CF 3 SO 3 B/acetone B/CH 3 CN :/DMF [73]. These workers also found that the CH 3 …”