Comparative νCO IR analysis of β-carbonylphosphonates [XC(O)CH2P(O)(OR)2: X = Me 1, Ph 2, OEt 3, NEt24 and SEt 5; R = Et] (series I) and β-carbonylsulfones [XC(O)CH2SO2R: X = Me 6, Ph 7, OEt 8, NEt29 and SEt 10; R = Et] (series II) along with ab initio 6-31G** calculations on 1a and 6a (R = Me) suggest the existence of only a single gauche conformer for series I. The negative carbonyl frequency shifts for both series follow approximately the electron-affinities of the Ï*CO orbital of the parent compounds MeC(O)X 11â15. The less positive asymmetric sulfonyl frequency shifts (ÎνSO2) for II in relation to the phosphoryl frequency shifts (ÎνPO) for I and the larger negative carbonyl frequency shifts for II with respect to the corresponding values for I are in line with the upfield 13C NMR chemical shifts of the carbonyl carbon for II compared to I. These trends agree with the shorter O(SO2)â¯C(CO) contact in comparison with the O(PO)â¯C(CO) one and are discussed in terms of OlpâÏ*CO charge transfer and electrostatic interactions, which are stronger for series II than for I, indicating that the sulfonyl oxygen atom is a better electron donor than the phosphoryl oxygen atom. Intrinsic geometrical parameters of OSâCH2 and OPâCH2 moieties seem to be responsible for this behaviour as indicated by X-ray study and ab initio calculations of dialkyl (methylsulfonyl)methylphosphonate MeSO2CH2P(O)(OR)2 (R = Et 18, Me 18a).
δ-羰基
膦酸盐[XC(O)
CH2P(O)(OR)2:XÂ =Â Me 1、Ph 2、OEt 3、NEt24 和
SEt 5;RÂ =Â Et](系列 I)和δ-羰基砜[XC(O) SO2R:XÂ =Â Me 6、Ph 7、OEt 8、NEt29 和
SEt 10;RÂ =Â Et](系列 II),以及对 1a 和 6a(RÂ =Â Me)进行的 ab initio 6-31G** 计算表明,系列 I 中只存在单一的高次构象。这两个系列的负羰基频移近似于母体化合物 MeC(O)X 11â15 的Ï*CO 轨道的电子亲和力。与 I 的
磷酰频移 (δ½PO)相比,II 的不对称磺酰频移 (δ½SO2)较小,而与 I 的相应值相比,II 的负羰基频移较大,这与 II 与 I 相比羰基
碳的上场 13C NMR
化学位移相一致。这些趋势与 O(SO2)â¯C(CO)接触比 O(PO)â¯C(CO)接触短的现象一致,并从 OlpâÏ*CO 电荷转移和静电相互作用的角度进行了讨论,II 系列的静电相互作用比 I 系列更强,表明磺酰基
氧原子是比
磷酰基
氧原子更好的电子供体。对(甲磺酰基)
甲基膦酸二烷基
酯 MeSO2 (O)(OR)2 (RÂ =Â Et 18, Me 18a)的 X 射线研究和 ab initio 计算表明,
OSâ
CH2 和 OPâ 分子的内在几何参数似乎是造成这种行为的原因。