Reactivity of [Pd{CH₂C(O)Me}Cl]<i>_n</i> toward Isocyanides

[Pd{CH2C(O)Me}Cl]n (1) reacts at low temperature with RNC (RNC:Pd = 1 or 2) to give [Pd2{CH2C(O)Me}2(μ-Cl)2(CNR)2] [R = tBu (2a), Xy (2b)] or trans-[Pd{CH2C(O)Me}Cl(CNR)2] [R = tBu (5a), Xy (5b)], respectively. These complexes decompose at room or higher temperature to give [Pd2{κ2-C,O-C(NHR)CHC(O)Me}2(μ-Cl)2] [R = tBu (3a), Xy (3b)] or [Pd{κ2-C,O-C(NHR)CHC(O)Me}Cl(CNR)] [R = tBu (6a), Xy (6b)], respectively, via insertion of the isocyanide into the Pd−C bond plus a tautomerization process from β-ketoimine to β-ketoenamine. The complex [Pd{κ2-C,O-C(NHXy)CHC(O)Me}Cl(NCMe)] (4b) can be obtained by reacting 1 with XyNC (Pd:XyNC = 1) in MeCN or complex 3b in CHCl3 with excess MeCN. Complexes trans-[Pd{C(NHR)CHC(O)Me}Cl(CNR)2] [R = tBu (8a), Xy (8b)] can be obtained (i) by reacting 1 with RNC (RNC:Pd = 3) or better (ii) by reacting 6 with 1 equiv of RNC at low temperature. The Pd(I) complexes [Pd2Cl2(CNR)4] [R = tBu (7a), Xy (7b)] are decomposition products obtained by heating 1 with RNC (RNC:Pd = 4−5), but they are detected in trace amounts in the reaction of 1 with RNC (RNC:Pd = 2−3). Addition of RNC and KTfO to a cooled suspension of 1 (Pd:RNC:KTfO = 1:3:1) gives complexes [Pd{CH2C(O)Me}(CNR)3]TfO [R = tBu (9a), Xy (9b)], which decompose at room temperature. The decomposition of 9b gives [Pd{κ2-C,O-C(NHXy)CHC(O)Me}(CNXy)2]TfO (10b), which can be obtained, as can the corresponding 10a, by reacting complexes 6 with 1 equiv of TlTfO and RNC. The reactions of the dimers 3 with PPh3 (Pd:PPh3 = 1) gives [Pd{κ2-C,O-C(NHR)CHC(O)Me}Cl(PPh3)] [R = tBu (11a), Xy (11b)], with PEt3 (PEt3:Pd = 2), trans-[Pd{C(NHR)CHC(O)Me}Cl(PEt3)2] [R = tBu (12a), Xy (12b)], and with Tl(acac) (Pd:acac = 1), [Pd{κ2-C,O-C(NHR)CHC(O)Me}(κ-O,O-acac)] [R = tBu (13a), Xy (13b)]. The crystal structures of 6a, 9b, 10a, and 10b have been determined. In complex 10b there are intermolecular π−π stacking and C−H···Pd agostic interactions giving dimers.配合物[Pd{CH₂C(O)Me}Cl]ₙ (1) 在低温条件下与异氰配体（RNC，RNC与Pd的摩尔比为1或2）反应，分别生成[Pd₂{CH₂C(O)Me}₂(μ-Cl)₂(CNR)₂] [R = 叔丁基(tBu, 2a)、二甲苯基(Xy, 2b)]或反式-[Pd{CH₂C(O)Me}Cl(CNR)₂] [R = tBu (5a)、Xy (5b)]。上述配合物在室温或更高温度下会发生分解，分别得到[Pd₂{κ²-C,O-C(NHR)CHC(O)Me}₂(μ-Cl)₂] [R = tBu (3a)、Xy (3b)]或[Pd{κ²-C,O-C(NHR)CHC(O)Me}Cl(CNR)] [R = tBu (6a)、Xy (6b)]，反应路径为异氰配体插入Pd-C键，同时伴随β-酮亚胺向β-酮烯胺的互变异构过程。配合物[Pd{κ²-C,O-C(NHXy)CHC(O)Me}Cl(NCMe)] (4b) 可通过两种途径制备：一是将1与XyNC（Pd与XyNC的摩尔比为1）在乙腈(MeCN)中反应，二是使配合物3b在三氯甲烷(CHCl₃)中与过量乙腈反应。反式配合物[Pd{C(NHR)=CHC(O)Me}Cl(CNR)₂] [R = tBu (8a)、Xy (8b)]可通过以下两种方式得到：(i) 1与RNC（RNC与Pd的摩尔比为3）反应，更优的方法是(ii) 在低温下使6与1当量RNC反应。钯(I)配合物[Pd₂Cl₂(CNR)₄] [R = tBu (7a)、Xy (7b)]是1与RNC（RNC与Pd的摩尔比为4~5）加热反应的分解产物；而当1与RNC的摩尔比为2~3时，仅能在反应体系中检测到痕量的该类配合物。将RNC与三氟甲磺酸钾(KTfO)加入到冷却的1的悬浮液中（Pd:RNC:KTfO的摩尔比为1:3:1），可得到配合物[Pd{CH₂C(O)Me}(CNR)₃]TfO [R = tBu (9a)、Xy (9b)]，该配合物在室温下会发生分解。9b的分解产物为[Pd{κ²-C,O-C(NHXy)CHC(O)Me}(CNXy)₂]TfO (10b)，该产物可与对应物10a一样，通过配合物6与1当量三氟甲磺酰氧基铊(TlTfO)及RNC反应制得。二聚体3分别与三苯基膦(PPh₃，Pd与PPh₃的摩尔比为1)、三乙基膦(PEt₃，PEt₃与Pd的摩尔比为2)以及乙酰丙酮铊(Tl(acac)，Pd与acac的摩尔比为1)反应，得到[Pd{κ²-C,O-C(NHR)CHC(O)Me}Cl(PPh₃)] [R = tBu (11a)、Xy (11b)]、反式-[Pd{C(NHR)=CHC(O)Me}Cl(PEt₃)₂] [R = tBu (12a)、Xy (12b)]以及[Pd{κ²-C,O-C(NHR)CHC(O)Me}(κ-O,O-acac)] [R = tBu (13a)、Xy (13b)]。已测定配合物6a、9b、10a及10b的晶体结构。在10b的晶体结构中，存在分子间π-π堆积作用与C-H···Pd agostic相互作用，使其形成二聚体结构。