Kharel, Sugam (2018-07). Topologically Novel Phosphorus Compounds and Metal Complexes. Doctoral Dissertation. Thesis uri icon


  • This dissertation details the synthesis of isomeric square planar platinum complexes bearing bridgehead diphosphine ligands with cis and trans geometries at platinum. The stabilities of these isomers have been discussed in detail. The topological properties of these complexes along with those of corresponding diphosphine ligands are examined. An overview on synthesis of oxide analogs of these ligands is presented. Section 1 gives an overview of the novel platinum diphosphine complexes with cis- (parachutes) and trans- (gyroscopes) geometries at platinum. Section 2 describes the reactions of cis-PtCl2(P((CH2)mCH=CH2)3)2 and Grubbs' first generation catal!yst and then hydrogenations to afford cis-PtCl2(P((CH2)n)3P) (cis-2; n = 2m+2 = b/12, c/14, d/16, e/18, f/20, g/22; 6-40%), derived from three fold interligand metatheses. The thermal behavior of the complexes is examined. When the bridges are sufficiently long, they rapidly exchange via an unusual "triple jump rope" motion over the PtX2 moieties. The relative stabilities of cis/trans and other types of isomers are probed by combinations of molecular dynamics and DFT calculations. Section 3 describes the reactions of P((CH2)mCH=CH2)3 (2.0 equiv; m = f/9, g/10, k/14) and PtCl2 in toluene to give trans-PtCl2(P((CH2)mCH=CH2)3)2 (trans-1f,g,k; 63-49%). Reactions of trans-1f,g with Grubbs' first generation catalyst (CH2Cl2/reflux) followed by hydrogenations (cat. PtO2) afford chromatographically separable gyroscope like trans-PtCl2(P((CH2)n)3P) (trans-2f,g, 3-19%; from interligand metathesis) and trans-PtCl2((H2C)nP((CH2)n)P(CH2)n)) (trans-2'f,g, 25-12%; from inter- and intraligand metathesis), where n = 2m+2. Under analogous conditions, trans-1k gives only cis-PtCl2(P((CH2)30)3P) (cis-2k, 39%). The stability of cis vs trans is established for 1g and 2'f,g in CH2Cl2 and toluene. Section 4 exploits the rapidly equilibrating in,in and out,out isomer of P((CH2)14)3P (1). U-tubes are charged with CH2Cl2 solutions of 1 (lower phase), an aqueous solution of K2MCl4 (charging arm; M = Pt, Pd), and an aqueous solution of excess KCl/KCN (receiving arm). The MCl2 units are then transported to the receiving arm until equilibrium is reached (up to 22 d vs. 100 h, KCl vs. KCN). Analogous experiments with K2PtCl4/K2PdCl4 mixtures show PdCl2 transport to be more rapid. Section 5 describes the reactions of (O=)PH(OCH2CH3)2 and BrMg(CH2)mCH=CH2 (4.9-3.2 equiv; m = a/4, b/5, c/6) to give the dialkylphosphine oxides (O=)PH((CH2)mCH=CH2)2 (2a-c; 77-81% after workups), which are treated with NaH and then ???-dibromides Br(CH2)nBr (0.49-0.32 equiv; n = a'/8, b'/10, c'/12, d'/14) to yield the bis(trialkylphosphine oxides) (H2C=CH(CH2)m)2P(=O)-(CH2)n(O=)P((CH2)mCH=CH2)2 (3ab', 3bc', 3cd', 3ca'; 79-84%). Reactions of 3bc' and 3ca' with Grubbs' first generation catalyst and then H2/PtO2 afford the dibridgehead diphosphine dioxides (O=)P(CH2)n((CH2)n')2P(=O) (4bc', 4ca'; 14-19%, n' = 2m + 2). Crystal structures of two isomers of the latter are obtained, out,out-4ca' and a conformer of in,out-4ca' that features crossed chains, such that the (O=)P vectors appear out,out.

publication date

  • July 2018