SIMULTANEOUS FIRST-SPHERE AND 2ND-SPHERE COORDINATION - ORGANOPALLADIUM CROWN-ETHER COMPLEXES AS METALLORECEPTORS FOR O-AMINOPYRIDINE DERIVATIVES

The complexes [Pd(L)(CH3CN)][BF4] (L = 2, 14-dithia[15]-m-cyclophane (L(o)), 5-oxa-2,8-dithia[9]-m-cyclophane (L(1)), 5,8,11-trioxa-2,14-dithia[15]-m-cyclophane (L(3))) were prepared by palladation of the respective thiacyclophane employing [Pd(CH3CN)(4)][BF4](2). For studies involving L(1), [Pd(L(1))(CH3CN)][CF3SO3] was also prepared in an analogous manner from [Pd(CH3CN)(4)][CF3SO3]. [Pd(L(0))(CH3CN)][BF4].CH3CN crystallized in the space group C2/c with a = 13.237(4) Angstrom A, b = 19.206(2) Angstrom A, c = 20.232(2) Angstrom A, V = 5168(3) Angstrom A(3), and Z = 8. The structure refined to R = 5.62% and R(w) = 4.76% for 3112 reflections with F-o(2) > 3 sigma(F-o(2)). [Pd(L(1))(CH3CN)][CF3SO3] crystallized in the space group P2(1)/c with a = 8.639(2) Angstrom A, b = 17.165(2) Angstrom A, c = 13.099(2) Angstrom A, beta = 91.85(2)degrees, V = 1941.3(5) Angstrom A(3), and Z = 4. The structure refined to R = 4.07% and R(w) = 4.67% for 1441 reflections with F-o(2) > 3 sigma(F-o(2)). [Pd(L(3))(CH3CN)][BF4] crystallized in the space group P ($) over bar 1 with a = 10.838(5) Angstrom A, b = 11.295(4) Angstrom A, c = 10.219(6) Angstrom A, alpha = 98.31(4)degrees, beta = 108.86(4)degrees, gamma = 102.78(4)degrees, V = 1122(2) Angstrom A(3), and Z = 2. The structure refined to R = 4.38% and R(w) = 4.71% for 2375 reflections with F-o(2) > 3 sigma(F-o(2)). The complexes with ether oxygen atoms act as metalloreceptors for o-aminopyridine derivatives (o-aminopyridine (oap), 2-amino-4-picoline (pie), cytosine (cyt)) via simultaneous first- and second-sphere coordination: the formation of a first-sphere Pd-N sigma bond and peripheral, second-sphere NH...O hydrogen bonds. NMR and X-ray crystallographic evidence for these interactions is presented and compared to that obtained with pyridine (py) as a substrate and [Pd(L(0))(CH3CN)][BF4] as a metalloreceptor, for which no second-sphere hydrogen bonding is possible. [Pd(L(1))(oap)][BF4] crystallized in the space group P2(1)/c with a = 10.056(2) Angstrom A, b = 18.889(2) Angstrom A, c = 11.294(7) Angstrom A, beta = 112.32(4)degrees, V = 1976(2) Angstrom A(3), and Z = 4. The structure refined to R = 6.95% and R(w) = 6.14% for 2326 reflections with F-o(2) > 3 sigma(F-o(2)). [Pd(L(3))(py)][BF4].CHCl3 crystallized in the space group P ($) over bar 1 with a = 11.982(3) Angstrom A, b = 12,858(3) Angstrom A, c = 10.048(2) Angstrom A, alpha = 103.59(2)degrees, beta = 99.63(2)degrees, gamma = 77.56(2)degrees, V = 1458.2(6) Angstrom A(3), and Z = 2. The structure refined to R = 5.14% and R(w) = 4.62% for 2079 reflections with F-o(2) > 3 sigma(F-o(2)). [Pd(L(3))(pic)][BF4] crystallized in the space group P ($) over bar 1 with a = 12.588(4) Angstrom A, b = 14.249(6) Angstrom A, c = 8.206(2) Angstrom A, alpha = 95.65(3)degrees, beta = 104.26(2)degrees, gamma = 66.07(3)degrees, V = 1304(2) Angstrom A(3), and Z = 2. The structure refined to R = 4.38% and R(w) = 4.72% for 3084 reflections with F-o(2) > 3 sigma(F-o(2)). [Pd(L(3))(cyt)][BF4].CH3CN crystallized in the space group P2(1)/c with a = 12.871(4) Angstrom A, b = 16.567(3) Angstrom A, c = 13.714(5) Angstrom A, beta = 101.53(3)degrees, V = 2867(2) Angstrom A(3), and Z = 4. The structure refined to R = 3.99% and R(w) = 4.57% for 2469 reflections with F-o(2) > 3 sigma(F-o(2)).