The preparation, characterization, and some properties of the C2Co2 cluster-bridged
bipyridine ligand (4-C5H4N)2C2Co2(CO)6 (1), diphosphine-chelated Pd(II)/Pt(II) complexes
[M(dppb)(H2O)2][OTf]2 (dppb = 1,4-bis(diphenylphosphino)butane, OTf = SO3CF3; 2, M =
Pd; 3, M = Pt), and the unique cationic cluster-containing Pd(II)/Pt(II) macrocycles
{[M(dppb)]-μ-[(4-C5H4N)2C2Co2(CO)6]}2[OTf]4 (4, M = Pd; 5, M = Pt) and {[M(dpab)]-μ-[(4-C5H4N)2C2Co2(CO)6]}2[OTf]4 (dpab = 1,4-bis(diphenylarsino)butane; 6, M = Pd; 7, M = Pt)
are reported. While ligand 1 is prepared by reaction of bis(4-pyridyl)acetylene with Co2(CO)8
in 61% yield, complexes 2 and 3 are prepared by reaction of M(dppb)Cl2 with silver triflate
followed by hydrolysis of the intermediates M(dppb)(OTf)2 in 96% and 94% yields,
respectively. Particularly interesting is that the self-assembly of ligand 1 with 2 and 3 results
in formation of the C2Co2 cluster-containing macrocycles 4 and 5 in 62% and 65% yields,
whereas 6 and 7 can be produced by self-assembly of 1 with diarsine-chelated complexes
[Pd(dpab)(H2O)(OTf)][OTf] and [Pt(dpab)(H2O)2][OTf]2 in 79% and 68% yields, respectively.
1−7 have been fully characterized by elemental analysis, spectroscopy, and particularly for
2−7 X-ray crystallography, and for 1, 4, and 7 by cyclic voltammetric techniques.
The synthesis, characterization, and some reactions of the tetrahedral Co 2 C 2 cluster-bridged bipyridine (4-C 5 H 4 NCO 2 CH 2 ) 2 C 2 Co 2 (CO) 6 (2) and the diarsine-chelated complexes Pd(dpab 6) have been investigated. While the bridged bipyridine 2 could be prepared by reaction of 4-pyridinecarboxylic acid 2-butyne-1,4-diyl ester 1 with Co 2 (CO) 8 in 86% yield, the chelated dichloride complexes 3 and 5 were obtained by reaction of K 2 PdCl 4 or (PhCN) 2 PtCl 2 with dpab in 90% and 77% yields. Further reactions of 3 and 5 with silver triflate followed by treatment with water afforded the corresponding chelated aqua/triflate complexes 4 and 6 in 92% and 88% yields. More interestingly, 4 and 6 were found to undergo self-assembly with 2 to give two cationic metallomacrocycles [OTf] 4 (7, M ) Pd; 8, M ) Pt) in 92% and 85% yields. X-ray crystal structures were determined for the Co 2 C 2 cluster-containing metallomacroycles 7 and 8, as well as bipyridine 2 and complexes 4 and 6.
Self-assembly of a ferrocenyl-bridged bipyridine ligand bpef [bpef=1,1'-bis(trans-2-pyrid-4'-ylethenyl)ferrocene] with silver triflate in CH 2 Cl 2 /MeOH or mercuric diiodide in MeCN/CH 2 Cl 2 gave the corresponding macrocyclic coordination complexes [bpef] 2 [AgSO 3 CF 3 ] 2 (1) and [bpef] 2 [Hg 3 I 6 ] (2) in 93% and 89% yields, respectively, whereas the pentaerythritolyl-bridged tetrapyridine ligand ptpc [ptpc=pentaerythritol tetrakis-(4-pyridinecarboxylate)] reacted with cobalt thiocyanate via self-assembly to afford the macrocyclic coordination polymer [Co(NCS) 2 (ptpc)] n (3) in 90% yield. The X-ray diffraction analyses for 1-3 confirmed their novel macrocyclic structures and revealed that (i) the two silver atoms in complex 1 have an essentially linear geometry with N-Ag-N bond angle of 175.7° and 172.9°, (ii) the geometry of the middle mercury atom in complex 2 is square-planar, while the other two mercury atoms in the other two complexes are tetrahedral, and (iii) all the cobalt atoms in complex 3 adopt an octahedral geometry. In addition, the synthetic procedure for the known tetrapyridine ligand ptpc has been improved.
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