PMID- 21766359
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20111102
LR  - 20110802
IS  - 1521-3765 (Electronic)
IS  - 0947-6539 (Linking)
VI  - 17
IP  - 33
DP  - 2011 Aug 8
TI  - Structure and bonding in stannadiphospholes and their dianions SnC2P2R2m (R=H, 
      tBu m=0, -2): a comparative study with C5H5+ and C5H5- analogues.
PG  - 9142-52
LID - 10.1002/chem.201100239 [doi]
AB  - The potential energy surfaces of both neutral and dianionic SnC(2)P(2)R(2) (R=H, 
      tBu) ring systems have been explored at the B3PW91/LANL2DZ (Sn) and 6-311+G* 
      (other atoms) level. In the neutral isomers the global minimum is a nido 
      structure in which a 1,2-diphosphocyclobutadiene ring (1,2-DPCB) is capped by the 
      Sn. Interestingly, the structure established by X-ray diffraction analysis, for 
      R=tBu, is a 1,3-DPCB ring capped by Sn and it is 2.4 kcal mol(-1) higher in 
      energy than the 1,2-DPCB ring isomer. This is possibly related to the kinetic 
      stability of the 1,3-DPCB ring, which might originate from the synthetic 
      precursor ZrCp(2)tBu(2)C(2)P(2). In the case of the dianionic isomers we observe 
      only a 6pi-electron aromatic structure as the global minimum, similarly to the 
      cases of our previously reported results with other types of heterodiphospholes. 
      The existence of large numbers of cluster-type isomers in neutral and 6pi-planar 
      structures in the dianions SnC(2)P(2)R(2)(2-) (R=H, tBu) is due to 3D aromaticity 
      in neutral clusters and to 2D pi aromaticity of the dianionic rings. Relative 
      energies of positional isomers mainly depend on: 1) the valency and coordination 
      number of the Sn centre, 2) individual bond strengths, and 3) the steric effect 
      of tBu groups. A comparison of neutral stannadiphospholes with other structurally 
      related C(5)H(5)(+) analogues indicates that Sn might be a better isolobal 
      analogue to P(+) than to BH or CH(+). The variation in global minima in these 
      C(5)H(5)(+) analogues is due to characteristic features such as 1) the different 
      valencies of C, B, P and Sn, 2) the electron deficiency of B, 3) weaker ppi-ppi 
      bonding by P and Sn atoms, and 4) the tendency of electropositive elements to 
      donate electrons to nido clusters. Unlike the C(5)H(5)(+) systems, all 
      C(5)H(5)(-) analogues have 6pi-planar aromatic structures as global minima. The 
      differences in the relative ordering of the positional isomers and ligating 
      properties are significant and depend on 1) the nature of the pi orbitals 
      involved, and 2) effective overlap of orbitals.
CI  - Copyright (c) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
FAU - Reddy, K Harikrishna
AU  - Reddy KH
AD  - Department of Inorganic and Physical Chemistry, Indian Institute of Science, 
      Bangalore-560012, India.
FAU - Usharani, Dandamudi
AU  - Usharani D
FAU - Nixon, John F
AU  - Nixon JF
FAU - Jemmis, Eluvathingal D
AU  - Jemmis ED
LA  - eng
PT  - Journal Article
DEP - 20110715
PL  - Germany
TA  - Chemistry
JT  - Chemistry (Weinheim an der Bergstrasse, Germany)
JID - 9513783
EDAT- 2011/07/19 06:00
MHDA- 2011/07/19 06:01
CRDT- 2011/07/19 06:00
PHST- 2011/01/21 00:00 [received]
PHST- 2011/07/19 06:00 [entrez]
PHST- 2011/07/19 06:00 [pubmed]
PHST- 2011/07/19 06:01 [medline]
AID - 10.1002/chem.201100239 [doi]
PST - ppublish
SO  - Chemistry. 2011 Aug 8;17(33):9142-52. doi: 10.1002/chem.201100239. Epub 2011 Jul 
      15.