Rare, Hexatomic, Boat-Shaped, Cross-Linked Bis(iminodiphenylphosphorano)methanediide Pincer Carbon Bridged Photoluminescent Copper Clusters Capped with Methyl or Halide Bridges

Abstract

The dimeric dilithium methanediide salt [Li2C(Ph2PNSiMe3)2]2 ([Li2L]2, L = [C(Ph2P=NSiMe3)2]2−) reacted with 6 equiv of [NEt4CuCl2] and 2 equiv of LiMe in THF or ether to give exclusively the six-copper cluster complex [Cu6L2(CH3)2] (1). Similarly, [Li2L]2 reacted with 3 equiv of the bimetallic copper halide complexes [(cod)2Cu2X2] (X = Cl, Br, I) in the same solvent to give good yields of three halide-capped six-copper clusters [Cu6L2(X)2] (X = Cl (2), Br (3), I (4)) with structures very similar to that of 1. These four hexacopper clusters (1−4) as a family show similar 31P NMR spectra with an AB pattern with slightly different chemical shifts but identical coupling constants in solution. The reactivity of 2 was explored, and it was demonstrated that 1 can be quantitatively generated by addition of 2 equiv of LiMe to 2. Moreover, the cluster [Cu6L2(OtBu)2] (5) with a similar cage structure is quantitatively generated by reaction of 2 with 2 equiv of NaOtBu in solution according to 31P NMR spectroscopy. An additional copper complex with a bicopper formulation, [Cu2L(PPh3)2] (6), was synthesized by reaction of [Li2L]2 with 2 equiv of [(NEt4)Cu(PPh3)Cl2]. We also observed a monocopper iodide complex with the doubly protonated parent methylene bridged ligand H2L, [CuI(H2L)] (7), as a minor component (about 10%) during the preparation of complex 4. Complexes 1−4, 6, and 7 were characterized by X-ray crystal diffraction. All four clusters (1−4) show a rare boat-shaped conformation of hexacopper clusters assembled by cross-linking of two copper atoms via geminal substitution on one bis(iminophosphorano)methanediide ligand. Two of these units combine along with two additional copper atoms to form the boat cluster. There is extensive direct Cu−Cu bonding. The cluster is doubly capped, top and bottom, by methyl groups (1) or halides (2−4, X = Cl, Br, I). All of these six-copper clusters absorb and emit in the UV−vis region. The absorption bands and photoluminescent wavelengths are substituent dependent; thus, optical properties of the complex are tunable by means of substitution of the capping ligands. The spectral and bonding characteristics were explored by means of Gaussian DFT calculations and NBO analysis.

Dianionic Carbon‐Bridged Scandium–Copper/Silver Heterobimetallic Complexes: Synthesis, Bonding, and Reactivity

“…1 H and 31 P{ 1 H} NMR spectral monitoringo ft he reactioni nC 6 D 6 showed the formation of the two new complexes 4 and 5 at 50 8C( Scheme 2). [10] The CuÀCb ond lengths in 5 range from 1.924 (7) to 1.952 (7) ,s imilar to those in 2 (1.947(9) )a nd [Cu 6 {C(PPh 2 NSiMe 3 ) 2 }X 2 ]( 1.942 (4) to 1.992 (2) ). The observed transmetallation, yieldingt he scandiumi odide 4 and the octanuclear copper(I) cluster 5,i si nl ine with the high halophilicity of the scandium ion, [12] and indicates the potential of 1 as a [C(SiMe 3 )PPh 2 S] 2À group transfer agent to access other metal alkylidene (or carbene) complexes.…”

“…Complex 5 has ac ubic Cu 8 core, with four Cu I ions on the same face coordinating a[ m,m'-C(SiMe 3 )PPh 2 S] 2À dianion,w hich is significantly different from the boat-types tructure of hexanuclearc opper(I) bis(iminophosphorano)methanediide clusters [Cu 6 {C(PPh 2 NSiMe 3 ) 2 }X 2 ]( X = Me, Cl, Br,I ). [10] The CuÀCb ond lengths in 5 range from 1.924 (7) to 1.952 (7) ,s imilar to those in 2 (1.947(9) )a nd [Cu 6 {C(PPh 2 NSiMe 3 ) 2 }X 2 ]( 1.942 (4) to 1.992 (2) ). The CuÀCu separations fall in the range of 2.644(2) to 2.895(2) ,w hich are in the range of the sum of the van der Waals radii of the Cu I centers.…”

“…[7h] As olution of 1 in C 6 D 6 was treated with one equivalent of CuI at room temperature andm onitoring of the reaction by 1 Ha nd 31 P{ 1 H} NMR spectroscopy revealed that 1 was slowly converted into the new complex 2.T he reaction was scaled up in toluenefor 18 h, whichafforded 2 as ay ellow solid in 70 %y ield (Scheme 1). [10] The ScÀCb ond length (2.248(9) )i n2 is significantly longer than that in the parent complex 1 (2.125(2) ), [7h] whereas the ScÀS bond lengths in these two complexes are similar,2 .582(3) in 2 and 2.552(1) in 1.T he distance between the Sc III and Cu I ions is 3.004(2) ,w hich is close to the sum of their covalent radii (i.e.,3 .02 ,c onsidering the covalentr adii of Sc as 1.70 and the one of Cu as 1.32 ). [10] The ScÀCb ond length (2.248(9) )i n2 is significantly longer than that in the parent complex 1 (2.125(2) ), [7h] whereas the ScÀS bond lengths in these two complexes are similar,2 .582(3) in 2 and 2.552(1) in 1.T he distance between the Sc III and Cu I ions is 3.004(2) ,w hich is close to the sum of their covalent radii (i.e.,3 .02 ,c onsidering the covalentr adii of Sc as 1.70 and the one of Cu as 1.32 ).…”

“…The observed transmetallation, yieldingt he scandiumi odide 4 and the octanuclear copper(I) cluster 5,i si nl ine with the high halophilicity of the scandium ion, [12] and indicates the potential of 1 as a [C(SiMe 3 )PPh 2 S] 2À group transfer agent to access other metal alkylidene (or carbene) complexes. [10] Reaction of 2 with 2,6-dimethylphenyl isocyanide in toluene at room temperature gives the isocyanide-coordinated complex 6 in 93 %y ield (Scheme 2a nd Figure 4). Complex 5 has ac ubic Cu 8 core, with four Cu I ions on the same face coordinating a[ m,m'-C(SiMe 3 )PPh 2 S] 2À dianion,w hich is significantly different from the boat-types tructure of hexanuclearc opper(I) bis(iminophosphorano)methanediide clusters [Cu 6 {C(PPh 2 NSiMe 3 ) 2 }X 2 ]( X = Me, Cl, Br,I ).…”

“…Complex 2 was characterized by NMR spectroscopy ( 1 H, 13 C{ 1 H} and 31 P{ 1 H}), elemental analysis, and single-crystal X-ray diffraction (Figure 1), confirming that 2 is an alkylidene-bridged scandium-copper heterobimetallic complex.I n2,t he CuÀCb ond length is 1.947(9) ,w hich is close to those in the copperb is(iminophosphorano)methanediide [Cu 6 {C(PPh 2 NSiMe 3 ) 2 }I 2 ]( 1.983(4) and 1.989 (4) ). [10] The ScÀCb ond length (2.248(9) )i n2 is significantly longer than that in the parent complex 1 (2.125(2) ), [7h] whereas the ScÀS bond lengths in these two complexes are similar,2 .582(3) in 2 and 2.552(1) in 1.T he distance between the Sc III and Cu I ions is 3.004(2) ,w hich is close to the sum of their covalent radii (i.e.,3 .02 ,c onsidering the covalentr adii of Sc as 1.70 and the one of Cu as 1.32 ). [11] By using as imilarp rocedure, the scandium-silver heterobimetallic complex 3 was obtained in 60 %y ield from ar eaction of 1 with AgI.…”