16-ELECTRON AND 18-ELECTRON RUTHENIUM(II) COMPLEXES OF THE NEUTRAL, POTENTIALLY TRIDENTATE TRIAMINE LIGAND 2,6-[BIS(DIMETHYLAMINO)METHYL]PYRIDINE (NN'N)

The potentially tridentate coordinating ligands NN'N (2,6-bis[(dimethy lamino)methyl]pyridine) and PNP (2,6-bis[(diphenylphosphino)methyl]pyr idine) react with [RuCl2(PPh3)(3)] to give [mer,trans-RuCl2(NN'N)(PPh3 )] (1) and [mer,trans-RuCl2(PNP)(PPh3)] (2), respectively. Complex 1 f unctions as a starting material for a variety of Ru[NN'N] complexes. I t reacts with either 1 or 2 equiv of AgOTf (OTf- = SO3CF3-) to yield m onocationic [RuCl(NN'N)(PPh3)]OTf (3) and [RuOTf(NN'N)(PPh3)]OTf (4), respectively. The molecular structure of 4 shows a pentacoordinated ru thenium(II) center with a square-pyramidal environment. The reaction o f 1 with either 1 or 2 equiv of AgOTf in the presence of MeCN results in the formation of the six-coordinate mono-or dicationic complexes [m er-RuCl(MeCN)(NN'N) (PPh3)]X (6a) (X = OTf-) and [mer,trans-Ru(MeCN)(2 )(NN'N)(PPh3)](OTf)(2) (7), respectively. At 55 degrees C in acetonitr ile, 1 converts quantitatively into 6b (X = Cl-) which is isostructura l with 6a. Reaction of polymeric [RuCl2(nbd)](n) (nbd = 2,5-norbornadi ene) with NN'N under a nitrogen atmosphere leads to the formation of n eutral, dinitrogen-bridged dimeric [(mu-N-2)(mer,trans-RuCl2{NN'N})(2) ] (8). The dinitrogen ligand is readily replaced when 8 is treated wit h CO, giving the neutral complex [mer,trans-RuCl2(CO)(NN'N)] (9). The 16-electron complex 3 reacts with CO giving [mer,cis-RuCl(CO)(2)(NN'N) ]OTf (10), involving the formation of [RuCl(CO)(NN'N)(PPh3)]OTf (11), followed by substitution of PPh3 by a second CO molecule. This stepwis e mechanism was confirmed by the isolation of 11. The 16-electron comp lex 4 reacts with CO under the formation of monocationic [mer-RuOTf(CO )(NN'N)(PPh3)]OTf (12) and a number of unidentified complexes. In the presence of ethyl alcohol, 4 reacts with CO to give monocationic [mer- RuOTf(CO)(NN'N)(HOEt)]OTf (13). The X-ray crystal structures of 1, 4, 6a, 8, 11, and 13 are reported in abbreviated form.